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Feasibility of Composting Wood and Cardboard Waste with Green Garden or Household Kitchen Waste: Trials Research Report Project code: WOO0044 Date of commencement of research: July 2005 Finish date: September 2006

Written by: ADAS UK Ltd

Published by: WRAP (The Waste & Resources Action Programme) The Old Academy, 21 Horse Fair, Banbury, Oxon, OX16 0AH Tel: 01295 819900 Fax: 01295 819911 www.wrap.org.uk WRAP Business Helpline: Freephone: 0808 100 2040 Date (published) June 2007 ISBN: 1-84405-320-2

Creating markets for recycled resources

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Authors Peter Davies, David Border, Andrew Urquhart. ADAS UK LTD Woodthorne Wergs Road Wolverhampton WV6 8TQ Acknowledgements The authors of this report would like to thank TRADA Technology for their assistance in the compilation of this report, and Norboard and B&Q for providing materials. WRAP and ADAS UK Ltd believe the content of this report to be correct as at the date of writing. However, factors such as prices, levels of recycled content and regulatory requirements are subject to change and users of the report should check with their suppliers to confirm the current situation. In addition, care should be taken in using any of the cost information provided as it is based upon numerous project-specific assumptions (such as scale, location, tender context, etc.). The report does not claim to be exhaustive, nor does it claim to cover all relevant products and specifications available on the market. While steps have been taken to ensure accuracy, WRAP cannot accept responsibility or be held liable to any person for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or misleading. It is the responsibility of the potential user of a material or product to consult with the supplier or manufacturer and ascertain whether a particular product will satisfy their specific requirements. The listing or featuring of a particular product or company does not constitute an endorsement by WRAP and WRAP cannot guarantee the performance of individual products or materials. For more detail, please refer to WRAP's Terms & Conditions on its web site: www.wrap.org.uk.

Feasibility of Composting Wood and Card – Trials Research Report 3

Executive summary....................................................................................... 7

1 Description and objective of work....................................................... 13

2 Overall Methodology............................................................................ 13 2.1 LITERATURE REVIEW .......................................................................................... 13 2.2 REVIEW OF CURRENT PRACTICES ........................................................................... 13 2.3 CASE STUDY .................................................................................................... 14 2.4 COMPOSTING TRIALS ......................................................................................... 14 2.5 EXPERIMENTAL DESIGN ....................................................................................... 14 2.6 GUIDANCE DOCUMENT ........................................................................................ 16

3 Literature survey 18

Wood residues ............................................................................................ 18 3.1 SOURCES OF WOOD RESIDUES............................................................................... 18 3.2 WOOD RESIDUE CONTAMINANTS............................................................................ 19 3.3 TYPES OF WOOD RESIDUES .................................................................................. 20

Waste cardboard......................................................................................... 21 3.4 WASTE CARDBOARD CONTAMINANTS....................................................................... 22 3.5 TYPES OF WASTE CARDBOARD............................................................................... 22

Composting in the UK ................................................................................. 23 3.6 LEGISLATIVE DRIVERS FOR THE UK COMPOSTING INDUSTRY .......................................... 23 3.7 THE COMPOSTING PROCESS.................................................................................. 23 3.8 COMPOSTING TECHNOLOGIES ............................................................................... 25

Composting wood wastes ........................................................................... 25 3.9 FORMALDEHYDE................................................................................................ 28 3.10 PAH ............................................................................................................. 29

Composting of waste cardboard................................................................. 29 3.11 MARKETS FOR COMPOSTS CONTAINING COMPOSTED WOOD OR CARDBOARD ....................... 30 3.12 QUALITY CONTROL AND STANDARDS FOR COMPOSTING WOOD WASTES AND CARDBOARD........ 32 3.13 INFLUENCE OF THE LITERATURE SURVEY UPON THE STRUCTURE OF THE COMPOSTING TRIALS .. 32 3.14 CONCLUSIONS.................................................................................................. 32

4 Operator Survey................................................................................... 33 4.1 METHODOLOGY ................................................................................................ 33 4.2 RESULTS......................................................................................................... 33 4.3 SUMMARY OF TELEPHONE INTERVIEWS.................................................................... 35

5 CASE STUDY......................................................................................... 40 5.1 WASTE TYPES SOURCES AND QUANTITIES................................................................. 40 5.2 COMPOST PROCESSING ....................................................................................... 40 5.3 PRODUCT AND QUALITY ...................................................................................... 41 5.4 RECOMMENDATIONS FOR THE TRIALS ...................................................................... 42

6 Composting trials................................................................................. 43 6.1 CARDBOARD .................................................................................................... 43 6.2 CHIPBOARD ..................................................................................................... 54 6.3 MEDIUM DENSITY FIBREBOARD (MDF) ................................................................... 70 6.4 MARKET WASTE ................................................................................................ 84


7 Conclusions .......................................................................................... 94 7.1 THE QUALITY OF COMPOST FROM THE TRIALS ............................................................ 94 7.2 THE PRACTICALITIES .......................................................................................... 94 7.3 ECONOMIC VIABILITY ......................................................................................... 95

8 Further information ............................................................................. 95

Appendix I................................................................................................... 96

WASTE AND RESOURCES ACTION PROGRAMME WASTE WOOD COMPOSTING SURVEY 2005....................................................................... 96

SECTION 1 – CONTACT DETAILS ....................................................................................... 96 SECTION 2 – COLLECTION OF WOOD WASTE......................................................................... 96 SECTION 3 – TYPES SOURCES AND QUANTITIES OF WOOD WASTE ............................................... 96 SECTION 4 – PROCESSING............................................................................................... 97 SECTION 5 – PRODUCT AND END USE ................................................................................. 97

Appendix II Temperature data ................................................................... 99

Appendix III - Protocols ........................................................................... 108

The trials ................................................................................................... 108 8.1 SOURCING MATERIALS ...................................................................................... 108 8.2 COMPOST PROCESSING ..................................................................................... 108 8.3 PARTICLE SIZE REDUCTION ................................................................................ 108 8.4 WEIGHING, MIXING AND WETTING ....................................................................... 108 8.5 EXPERIMENTAL DESIGN ..................................................................................... 108 8.6 SAMPLING AND ANALYSIS .................................................................................. 109 8.7 SAMPLING METHODS ........................................................................................ 109

Appendix IV – Time temperature profiles ................................................ 111

REFERENCES ............................................................................................. 132


TABLE OF FIGURES Figure 1 Summary of composting protocol for feedstock mixed with garden waste............................. 15 Figure 2 Summary of composting protocol for trials involving kerbside collected kitchen and garden

waste ................................................................................................................................... 15 Figure 3 Classification of composting technologies .......................................................................... 25 Figure 4 Wood waste prior to treatment at Harewood ..................................................................... 40 Figure 5 Co-composting wood and green waste ............................................................................. 41 Figure 6 Composted production in windrow .................................................................................... 42 Figure 7 Source separated kerbside waste..................................................................................... 44 Figure 8 Source separated kerbside waste with additional cardboard ................................................ 44 Figure 9 Scan of the time-temperature profile of the first cardboard trial (CARD 1) ............................ 47 Figure 10 Chipboard stacked on pallets as delivered........................................................................ 54 Figure 11 Close view of the chipboard............................................................................................ 55 Figure 12 Large pieces of broken chipboard.................................................................................... 57 Figure 13 Shredded chipboard....................................................................................................... 58 Figure 14 Wetting the chipboard and garden waste......................................................................... 58 Figure 15 Mixing the chipboard and garden waste using the shredder and bucket loader.................... 59 Figure 16 Time temperature profile of chipboard tunnel 2................................................................ 60 Figure 17 The compost product derived from 10% inclusion of chipboard with garden waste.............. 62 Figure 18 Close up of compost product derived from 5% inclusion of chipboard with kerbside collected

garden and kitchen waste ...................................................................................................... 63 Figure 19: The reduction in formaldehyde concentrations during composting chipboard ..................... 68 Figure 20 MDF fines ..................................................................................................................... 70 Figure 21 MDF and garden waste composted in windrows ............................................................... 72 Figure 22 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF DRY 1)

........................................................................................................................................... 73 Figure 23 Fate of formaldehyde during composting 10% MDF with garden waste or kerbside collected

garden and kitchen waste ...................................................................................................... 82 Figure 24 Market waste ................................................................................................................ 84 Figure 25 In-vessel time and temperature profile of the first market waste trial (market waste 1) ....... 86 Figure 26 In-vessel time and temperature profile of the second market waste trial (market waste 2)...87 Figure 27 Scan of the in-vessel time-temperature profile computer print out of the Tunnel Control.... 111 Figure 28 Scan of the in-vessel time-temperature profile computer print out of the CARD 1 trials ...... 112 Figure 29 Scan of the in-vessel time-temperature profile computer print out for the CARD 2 trial ...... 113 Figure 30 Scan of the in-vessel time-temperature profile computer print out for the EXTRA CARD 1 trial

......................................................................................................................................... 114 Figure 31 Scan of the in-vessel time-temperature profile computer print out for the EXTRA CARD 2 trial

......................................................................................................................................... 115 Figure 32 Time and temperature profile of the Tunnel Chip 1 (kerbside kitchen, garden and chipboard)

......................................................................................................................................... 116 Figure 33 Time and temperature profile of the Tunnel Chip 2 (kerbside kitchen, garden and chipboard)

......................................................................................................................................... 117 Figure 34 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF DRY 1)

......................................................................................................................................... 118 Figure 35 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF DRY 2)

......................................................................................................................................... 119 Figure 36 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF WET 2)

......................................................................................................................................... 120 Figure 37 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF WET 2)

......................................................................................................................................... 121 Figure 38 Scan of the time and temperature profile of the first market waste trial (market waste 1). 122 Figure 39 Scan of the time and temperature profile of the second market waste trial (market waste 2)

......................................................................................................................................... 123


LIST OF TABLES Table 1 Experimental treatment .................................................................................................... 14 Table 2 Common sources and types of wood residues ..................................................................... 19 Table 3 Potential contaminants in wood residues ............................................................................ 19 Table 4 Organic wastes composted in the UK 2003/0412 .................................................................. 23 Table 5 Summary of telephone interviews ...................................................................................... 36 Table 6 Analysis of the cardboard trial feedstocks ........................................................................... 45 Table 7 Incorporation rate of the composting mixes ........................................................................ 45 Table 8 The weights of feedstocks added....................................................................................... 46 Table 9 Temperature and moisture monitoring in windrows after processing in-vessel........................ 48 Table 10 Mass balance of waste, compost and oversize material ...................................................... 49 Table 11 Physical and chemical characteristics of compost produced from kerbside collected garden,

kitchen and cardboard waste.................................................................................................. 49 Table 12 The nutrient value of compost produced in the card trials .................................................. 50 Table 13 Comparison of the composting trials using a cardboard containing feedstock to PAS 100 ...... 51 Table 14 Comparison of the heavy metals at the start and end of the process, and against EN13432 in

the cardboard feedstock......................................................................................................... 52 Table 15 Chipboard analysis.......................................................................................................... 55 Table 16 Incorporation rate of chipboard in the trial runs ................................................................ 56 Table 17 Chemical analysis of the garden waste and chipboard feedstock mixture ............................. 56 Table 18 Chemical analysis of the garden, kitchen and chipboard feedstock mixture .......................... 57 Table 19 Temperature and moisture contents during the windrow phase of composting chipboard with

garden or kerbside collected garden, kitchen and cardboard waste ............................................ 61 Table 20 Mass balance of the chipboard trials................................................................................. 62 Table 21 Physical and chemical analysis of the chipboard compost ................................................... 63 Table 22 Nutrient analysis of the chipboard compost....................................................................... 64 Table 23 Comparison of a garden and kerbside chipboard compost with PAS 100 .............................. 65 Table 24 Comparison of other contaminants in compost with and without chipboard.......................... 66 Table 25 Formaldehyde reduction during the composting process of feedstock containing chipboard...67 Table 26 MDF Analysis.................................................................................................................. 71 Table 27 Garden waste and MDF chemical and physical analysis ...................................................... 71 Table 28 Kerbside collected waste and MDF chemical and physical analysis....................................... 71 Table 29 Summary temperature and moisture monitoring during the windrow phase of the MDF trials 74 Table 30: Mass balance of MDF trials before and after composting .................................................. 75 Table 31 General characteristics of the compost derived from garden waste and MDF........................ 75 Table 32 General characteristics of the compost derived from kerbside collected garden and kitchen

waste and MDF ..................................................................................................................... 75 Table 33 Nutrient analysis of the composts derived from MDF with garden or garden and kitchen waste

........................................................................................................................................... 77 Table 34 Comparison of the composts derived from MDF and garden waste or garden and kitchen waste

to the PAS 100 ...................................................................................................................... 78 Table 35 Other contaminants ........................................................................................................ 80 Table 36 Analysis of the cardboard trial feedstocks ......................................................................... 84 Table 37 Incorporation rate of the composting mixes ...................................................................... 85 Table 38 Weights of the feedstocks added ..................................................................................... 85 Table 39 Temperature and moisture monitoring in windrows after processing in-vessel ...................... 89 Table 40 Mass analysis of the end product ..................................................................................... 89 Table 41 Physical and chemical characteristics of compost produced from market waste .................... 90 Table 42 Nutrient value of the market waste derived compost compared to controls .......................... 90 Table 43 Comparison of the market waste composting trials to PAS 100 ........................................... 91 Table 44 Windrow temperature and moisture monitoring data of the controls.................................... 99 Table 45 Temperature and moisture monitoring for the windrow phase of the card trials.................. 100 Table 46 Temperature and moisture monitoring of the windrow phase of the chipboard trials........... 102 Table 47 Temperature and moisture monitoring during the windrow phase of the MDF trials ............ 104 Table 48 Temperature and moisture monitoring during the windrow phase of the market waste trials106 Table 49 Experimental treatments ............................................................................................... 109 Table 50: The Analysis required by PAS 100 ................................................................................ 109 Table 51: Non PAS 100 compost contaminants in the chipboard trials............................................ 124 Table 52 Non PAS 100 contaminants in the MDF trials................................................................... 128


Executive summary This study was carried out to determine the feasibility of composting wood and cardboard waste with

garden or household kitchen waste. The work was carried out in two phases. The first phase was a

review of the published information, and assessment of current practice. This information was then

used to establish composting trials in the second phase, the results of which are also reported.

The Literature Survey revealed the following:

Types of wastes and contaminants

• There are many different sources of wood wastes suitable for composting. These include forest

harvesting waste, primary processing waste (e.g. sawmills), secondary processing waste (e.g.

furniture manufacturing), wood waste from residue traders, construction & demolition waste, and

components of municipal and commercial wastes;

• Wood residues can consist of a number of forms in addition to virgin wood. These include layered

composites (e.g. plywood), particle composites (e.g. chipboard) and fibre composites (e.g. MDF);

• Wood wastes often contain contaminants of a variety of types, including physical contaminants

(e.g. paints, laminates, veneers) and chemical contaminants such as preservatives;

• Cardboard wastes can be generated from cardboard manufacturing and packaging, and can form a

major component in kerbside collected wastes;

• Cardboard often contains physical contaminants (e.g. staples, plastics) and chemical contaminants,

(e.g. adhesives and printing ink); and

• When composting wood wastes and cardboard wastes it is essential to be aware of the differences

between the different types and to recognise the potential importance of some of the

contaminants.

Composting in the UK

• In 2004/05 2.67 million tonnes of organic wastes were composted (The Composting Association,

2006);

• 16% of local authorities allowed the collection of waste cardboard with kerbside collected green

waste, and 16% allowed the collection of cardboard with kerbside collected kitchen waste;

• In 2003 composting was identified as a disposal option for wood waste by 6.9% of companies

accounting for 11% of the wood waste produced;

• The legislative drivers for the development of the UK composting industry include the EU Landfill

Directive, The Waste and Emissions Trading Act, the Landfill Allowance Trading Scheme, and UK

recycling targets; and

• Many different composting technologies are used in the UK, including windrow composting, aerated

static piles, horizontal and vertical continuous systems, and batch tunnels. All can be suitable for

the composting of wood waste and waste cardboard.


Composting wood wastes

• Most wood waste producers have their wood waste collected by third parties for recycling or

composting;

• A number of WRAP reports have looked at different aspects of the suitability of treated woods as

feedstocks in composting operations;

• The cost of composting wood waste has been estimated to be between £10 and £30/tonne

depending upon volume, the composting technology chosen, and a number of other factors;

• Factors determining the suitability of wood waste for composting include the presence of

contaminants, (e.g. bonding agents, preservatives, paints and other chemicals, plastics), continuity

of supply, marketability of products manufactured, and economic viability;

• Health and safety considerations have to be taken into account in composting wood wastes

containing these chemicals, (e.g. emission of formaldehyde from some treated woods);

• A number of studies have shown that some of these chemicals are readily broken down by the

composting process while others are resistant to breakdown by this method;

• The range of chemicals used to preserve and otherwise treat wood has changed considerably in

recent years. However, the continuing presence in older waste wood of no longer used chemicals

must be recognised;

• Wood can fit in well within an existing composting process as long as compensation is made for

factors including low moisture, and a high C:N ratio. The wood must be comminuted to produce a

particle size of not more than a few centimetres. The high levels of lignin within the wood make the

material slow to compost compared to many other wastes such as green waste; and

• Poorly composted wood can produce phytotoxic effects on plant growth.

Composting of waste cardboard

• Cardboard is routinely composted as a component in kerbside collected material although in many

cases it is regarded as a difficult material and collected separately for recycling by other means;

• Various forms of waste cardboard such as multilayered cardboard boxes, Biopol coated cardboard,

corrugated cardboard, and waxed cardboard have been successfully composted;

• Pre-wetting and the addition of supplemental nitrogen can allow a greater proportion of cardboard

to be added to a composting mixture without slowing down the process;

• As long as the wood and cardboard wastes are properly comminuted before composting, and other

steps are taken to compensate for their low moisture and high C:N ratio, their presence in the

feedstock should not affect the marketability of the final product; and

• The most important specification for composts containing composted wood wastes and cardboard is

the BSI PAS 100 along with other industry-specific standards such as those for landscaping and top

soil manufacture.

Fifteen composting operators were contacted by telephone to obtain an overview of the current state of

wood and cardboard composting within the UK.

The Operator Survey revealed the following:


Types, quantities and sources

• Three operators composted wood wastes, 5 composted cardboard waste, 4 composted wood and

cardboard waste, and 3 did not compost either wood or cardboard waste;

• It was not possible to clearly identify the specific types of wood wastes composted. Instead,

composters used a rudimentary classification, e.g. clean, high grade, low grade, contaminated;

• Three operators composted between 2,000 and 5,000 tonnes of wood waste a year. Another

collected 14,000 tonnes a year of wood waste but composted only a small part of this material; and

• Material was sourced mainly from Civic Amenity sites, kerbside collected material, and commercial

sources.

Composting of wood wastes and cardboard

• The inclusion rate of wood was difficult to determine but ranged from insignificant to 10-15%

(w/w);

• The inclusion rate for cardboard ranged from 10% (w/w) to more than 10% with excess cardboard

being screened out at the end of the process;

• Both wood and cardboard were often pre-wetted prior to adding to a composting mixture.

• Standard shredders were used to comminute the wastes;

• Problems were often encountered with the wastes drying out and with dust emissions as wood

waste was shredded;

• Composting of mixtures containing the wood and cardboard wastes was carried out in the same

way as with green waste;

• A higher gate fee than for green waste was obtained for the wood wastes, and the income

obtained from compost sales was not affected, but there were higher processing costs;

• The main problem relating to quality of feedstocks was the presence of hinges, nails and glass in

the wood wastes. Most composters avoided composting wood contaminated with paints and

preservatives;

• The quality of the end product was determined, to an extent, by the inclusion rate of both the

wood wastes and the cardboard waste; and

• The main uses of composts derived from wood and cardboard containing feedstocks were as

mulches or soil improvers in land restoration, agriculture or landfill restoration.

Case Study

• Yorwaste’s Harewood Composting Site was visited as part of the project. The site takes in civic

amenity waste including doors, panels and tables;

• Cleaner wood waste is sent on to recyclers while lower quality wood waste is composted;

• Wood waste is shredded to <50 mm and mixed with shredded green waste and then co-composted

with liquid wastes; and

• The end product is used for landfill restoration.

The above preliminary work produced valuable information that has been used to inform the design of

the composting trials that form the bulk of this project.


Literature survey

• Most previous analytical studies have been carried out at a bench top or small scale. There is a

need for similar work to be carried out at a full commercial scale;

• Most composting studies have been carried out using a basic windrow system. There is a need for

such work to be carried out within a more controlled environment;

• Upper limits must be set for inclusion rates of wood and cardboard in composting feedstock

mixtures;

• There is a strong argument for adding water and nitrogen directly to the wood and cardboard

components at the start of the composting process;

• The origin of the wastes and their likely contaminants should be determined prior to composting.

• Physical contaminants should be removed before or after composting;

• Efficient comminution of both wood and cardboard wastes is essential; and

• Composting should be carried out to an acceptable standard such as PAS 100.

Operator survey

• The addition of water to the wastes, possibly in the form of a liquid waste including nitrogen, is

called for;

• Upper limits should be set for inclusion rates; and

• Care should be taken in reducing dust emissions during shredding.

The composting trials revealed the following:

Cardboard trials

The cardboard composted was collected from two sources. The first source was a kerbside collection of

garden, kitchen and cardboard. The level of cardboard received in these collections is difficult to

control. Given these difficulties, a robust composting technology is required as the feedstock may not

always be optimal for composting. The second source was extra card that had been separated from

fruit deliveries.

The composting of cardboard is feasible if precautions are taken. The addition of dry cardboard can dry

out the composting process. Therefore, the cardboard needs to be sufficiently wetted. Wetting at the

start of the process as opposed to during the process can minimise run-off. Shredding cardboard is

quite difficult and compost producers should consider the type of shredder they purchase if they intend

to process card. The hammer and flails shredder used in this trial was adequate but did not shred the

entire card feedstock. A hammer shredder is likely to perform better, while a chipper shredder will not

be suitable for card. The data show that the compost can reach adequate temperatures during the

process.

A quality compost product was produced from trials which met the Publicly Available Specification for

Composted Materials (PAS 100). It was therefore feasible to compost cardboard as received (16% card)

in a kerbside collection. Also the trials showed that the addition of 5% extra card (by weight) to mimic

an abnormally high cardboard inclusion rate did not have deleterious effect on the composting process.

Moreover, the product had desirable characteristics for plant growth and had a fibrous and light


structure. However, the compost was screened to 10 mm losing approximately 30% as oversize

material. A significant proportion of this oversize material was organic matter. A more powerful

shredder and more rigorous turning regime may have enabled a quality compost to be produced at 25

mm, but contamination by plastic packaging was a major limiting factor to increasing the proportion of

product recovered.

During the winter the proportion of cardboard in the kerbside collection increased (as a consequence of

there being less green waste). This material could still be composted but it was more difficult due to a

lack of structure, high carbon content, and a greater proportion of the plastic contaminated kitchen

waste.

Chipboard trials

Large flat boards (3m x 2m) for the composting trials were sourced from B&Q. The chipboard was

composted with green waste in windrows at a 10% inclusion rate and kerbside collected green and

kitchen waste was composted for one week in batch tunnels at a 5% inclusion rate followed by windrow

composting.

The material was difficult to compost in comparison to green waste. Particle size reduction required

three processing stages in comparison to one shredding stage used for green waste. Furthermore,

additional health and safety precaution needed to be put in place to prevent exposure to formaldehyde.

Adequate temperatures were easily met for both invessel and windrow composting. However, the

material dried out quickly and it was both difficult and time-consuming to re-wet using a water bowser.

At the end of composting, the material was screened to produce a 10 mm product. The product was of

high quality, characterised by adequate nutrient levels to support plant growth, it had a lower bulk

density and conductivity compared to green waste. Nitrogen levels were elevated in all the test

composts compared to the controls. The test composts met the PAS 100 specification in all aspects,

with the exception of one trial that had a high stones content. There were also signs of chlorosis in the

bioassay trials, but these were not significant enough to be considered an abnormality. High

ammonium-N levels were implicated as the cause of chlorosis where low formaldehyde levels were

present. This was further supported by test composts with low ammonium levels and no observable

symptoms.

Contaminants associated with wood wastes including heavy metals, organics including phenols and

glues were analysed, and were all found to be low compared to green waste compost.

Medium Density Fibreboard (MDF) trials

The MDF had been reduced in particle size before arrival on site. The material was light and had a

‘fluffy’ appearance. It was incorporated in both green waste and kerbside collected green and kitchen

waste trials at 10% (w/w). For half of the trials the MDF was pre-soaked in water prior to composting.

The material was difficult to compost. It tended to clump, especially when wetted, and was easily

blown around when dry, which made uniform mixing difficult. As with chipboard the material dried very


easily, and was then difficult to re-wet as a large proportion of the water applied did not penetrate the

surface. This was not detrimental to achieving composting temperatures but more degradation would

have likely occurred if the material could have been re-wetted more thoroughly.

The MDF and green waste derived compost had higher nitrogen levels compared to green waste alone,

while the nitrogen levels in MDF and green and kitchen waste were similar to the green and kitchen

waste control. The compost could meet PAS 100 however, one compost had a high concentration of

lead, and three of the eight composts had higher than permitted levels of physical contaminants, which

could be attributed to paper being included as a physical contaminant.

The only contaminant at high levels was formaldehyde. This was measured at both the start and after

12 weeks composting. The formaldehyde levels in the compost derived from MDF mixed with green

waste and kitchen waste behaved as expected, decreasing during the process, and the rate of decrease

was higher where pre-soaked MDF had been incorporated. The formaldehyde levels in the compost

derived from MDF mixed with green waste, however, did not behave as expected as the formaldehyde

levels appeared to increase with time, possible explanations for this are given in the MDF results

section.

Market waste trials

Market waste was composted in two trials with kerbside collected green and kitchen waste. The high

moisture content of the fruit and vegetable waste limited the inclusion rate and made composting more

difficult. During composting, adequate temperatures were recorded to meet the Animal By-product

Regulations and to promote degradation throughout the 12 week process. Although the compost

produced was of suitable chemical and physical quality measured against PAS 100 and had sufficient

nutrient availability, it failed to adequately support plant growth. The plants exhibited phytotoxic

effects, and therefore a lower incorporation rate of market waste was recommended.


1 Description and objective of work

This report covers a project undertaken to determine the feasibility of composting wood and cardboard waste with green garden or household kitchen waste. It encompasses optimising the co-composting of the materials, identifying the effects of wood and/or cardboard in the composting mix and assessing the quality of the compost produced. The research work was carried out in three parts. The first was to assess published information and the second to determine current industry practice. This information was then used to carry out the third phase, the design and carrying out of practical trials to compost card and wood waste. The objectives of the work were to: • Review published information and current practice on the composting of wood and cardboard

waste; • Design and undertake composting trials using windrow and in-vessel technologies on a commercial

scale; • Assess the quality of the compost produced from the trials; • Assess the practicalities and economic viability of the composting option; and • Use the results to prepare a guidance document on how to compost wood and/or cardboard with

organic municipal waste.

2 Overall Methodology

This report consists of three components: • A literature Review; • A review of current practices of existing UK composters; and • Composting trials using wood and cardboard, and an assessment of the compost quality

2.1 Literature review The literature review has been carried out to assess the recent and current composting operations concerning cardboard and/or wood waste, specifically focusing on information on the composting of panelboard waste. Information was gathered on: • The source, type, quantity and relative proportions of the feedstocks; • Feedstock preparation/pre-treatment; • Processing conditions and timescales involved; • Compost quality compared with the PAS 100 specification, including the fate of any chemical

contaminants such as inks and panelboard resins; • Compost end uses and sales prices; • Any concerns/difficulties associated with composting cardboard and/or wood wastes; and • Any perceived benefits from composting wood or cardboard.

2.2 Review of current practices A review of current practices was obtained through telephone interviews of 15 compost producers. The information obtained includes:


• Types, sources and quantities of wood and cardboard-containing wastes; • The percentage of wood waste or cardboard that is incorporated into green/kerbside waste for

composting; • The advantages of composting wood or cardboard in terms of economics, processing and compost

quality; • Compost quality – whether the compost produced meets PAS 100, or whether any other standard

or assessment of the compost quality is carried out; • End uses of the resulting compost for both the product types and markets to which they are sold; • Difficulties in processing or using the composted materials; and • Sales price

2.3 Case study A case study was described to provide greater detail than could be obtained during a telephone interview. The case study examined: • Waste types sources and quantities; • Compost processing; • Product quality; and • Recommendations for the trials.

2.4 Composting Trials Information gathered within the literature review and review of current practices was used to define the composting trials. The aim of the trials was to optimise and demonstrate the effectiveness of cardboard and/or wood waste composting, focusing on the co-composting of individual materials as well as mixtures of wood and cardboard waste. For each trial the following activities were established: • Sorting, storage, pre-treatment requirements; • Processing conditions which optimise the composting process e.g. requirements for water, turning,

shredding etc; • The maximum amount of cardboard and/or wood waste that can be included within the composting

mix without affecting the optimum composting process; • Any benefits or difficulties observed from including cardboard and/or wood waste in the composting

mix; • Carrying out the trials on a commercial scale • Analysing data on the feedstocks through direct analysis and information obtained from waste

producers; and • Analysing the chemical and physical composition of the feedstocks.

2.5 Experimental design The trials were designed as shown in Table 1. Each trial was carried out in duplicate and compared to the controls. Medium Density Fibreboard (MDF) WET refers to a trial where the MDF was wetted before mixing. For the Medium Density Fibreboard (MDF) DRY trials the boards were mixed before being wetted. A detailed protocol is provided in the Appendix.

Table 1 Experimental treatment In-vessel Windrow

control (Garden, kitchen and card) control (green waste) Cardboard 1 (as received) Cardboard 2 (as received) Cardboard extra 1 (5% extra w/w) Cardboard extra 2 (5% extra w/w) Chipboard (5% w/w) Chipboard (10% w/w) Chipboard (5% w/w) Chipboard (10% w/w) Market 1 (20% w/w) Market 2 (20% w/w) MDF WET (10% w/w) MDF WET (10% w/w) MDF WET (10% w/w) MDF WET (10% w/w) MDF DRY (10% w/w) MDF DRY (10% w/w) MDF DRY (10% w/w) MDF DRY (10% w/w)


The composting protocol used is summarised in Figure 1 for the trials involving green waste, and Figure 2 for those involving garden, catering and card waste. All the feedstocks were shredded prior to composting.

Figure 1 Summary of composting protocol for feedstock mixed with garden waste

Figure 2 Summary of composting protocol for trials involving kerbside collected kitchen and

garden waste

In some trials wetting was carried out before mixing

TRIAL FEEDSTOCK GREENWASTE

SHRED

MIX

WINDROW COMPOSTING8 WEEKS

FURTHER COMPOSTING(MATURATION) 4

WEEKS

WET

SCREEN


2.6 Guidance document

TRIAL FEEDSTOCK GREEN WASTE CATERINGWASTE AND CARD

WET

SHRED

MIX

INVESSEL COMPOSTINGONE WEEK

WINDROW COMPOSTING7 WEEKS

FURTHER COMPOSTING(MATURATION) 4

WEEKS

SCREEN


The evidence based gathered from this report will be used to compile a guidance document for the industry, which will include: • The types of cardboard and wood waste that composters can use and those they cannot • Physical contaminants, inks, dyes and organic residues; • Methods of collecting these wastes; • The principles of site management and process control; • Methods composters use to optimise the composting of these wastes by windrow and in-vessel

composting; • Standards and test procedures, for example PAS 100, that composters should apply to composts

made from these wastes; • The effect the use of these wastes can have on recycling costs and income; • Sources for further information.


3 Literature survey

This literature review has been carried out as part of WRAP Project WOO0044 – “Feasibility of composting wood and cardboard waste with green garden or household kitchen waste”. The purpose of the study is to review published literature relating to the composting of wood residues and cardboard waste. One reason for this is that wood waste, including disposal to landfill, can cost manufacturers between 5% 1 and 10% 7 of turnover. This report first looks at the sources and types of wood waste and cardboard waste produced in the UK, and then examines the common contaminants in these materials of relevance to the composting process. A brief review of the state of composting in the UK is presented, along with an outline of the composting technologies currently available, followed by an examination of published data specifically on the composting of wood residues and waste cardboard, and the use of the resultant composts. The report concludes with a summary of how this literature review provides guidance to the nature of the proposed wood and cardboard composting trials. The literature and operator surveys presented in this report have been prepared in order to determine: • The current state of knowledge regarding the composting of wood and cardboard with green waste

or household kitchen waste; • Methodologies for the composting these wastes; • Potential problems, including health and safety considerations and environmental effects, that

might be encountered during the composting of these wastes; • The current state of the composting of these wastes in the UK; and • The attitude of UK composters towards the composting of these wastes and the potential for the

expansion of this activity. The above data was collected in order to inform the design of composting trials to optimize the processing of these wastes and to encourage the use of these wastes in commercial composting facilities.

WOOD RESIDUES A number of important factors have to be considered in determining if a particular wood residue is suitable for composting, including the source of the residue, the presence of any contaminants, and the nature of the wood residue itself.

3.1 Sources of wood residues A survey carried out by TRADA2 has produced basic data for the types of wood residues generated in the UK. The sources and types of wood residues as shown Table 2.


Table 2 Common sources and types of wood residues Sector Source Wood residue Forest harvesting Thinning, logging, harvesting

operations Bark, branches, leaves, rejected trees, roots, stumps, thinnings, top wood

Primary processing Sawmills, board-mills Bark, edgings, off cuts, rejects, sawdust, slab-wood, shaving, wood chip

Secondary processing Flooring, furniture, joinery, pallet and packaging manufacture

End-trim, damaged products, off cuts, reject material/products, sander dust, sawdust, screening and grinding dusts, shavings, veneer clippings/waste

Traders Distributors, importers, merchants of timber products, wood residue traders, timber salvage operations

Possible secondary processing residues and rejected/damaged products

Construction and demolition Construction, demolition, refurbishment, de-construction, scaffolders

Cable drums, coated materials, cladding, dimension timber, doors and door frames, fences, flooring, framing timbers, pallets and packaging (whole and broken), panels and engineered wood composites using adhesives, piles, poles, solid wood, stakes, window frames

Landfill / Municipal solid waste Residential, commercial, institutional and industrial products

Residential, commercial, institutional and industrial end-of-life products including durable and non durable goods, containers and packaging, furniture, toys, paper and board, scrap timber and panels, garden and parkland waste (leaves, grass clippings, bush and tree clippings and removals).

References: Falk 1997, Fehrs 1996, Hall 1971, Mckeever et al 1995, Marutzky 1997, Skog and Rosen 1997

3.2 Wood residue contaminants In principle, many of these wood residues could be used as composting feedstock, although the TRADA report lists a wide range of physical and chemical contaminants that may be present (Table 3).

Table 3 Potential contaminants in wood residues

Mechanically separable Physically and chemically separable Aggregates, bricks, ceramic tiles, concrete, glass, gypsum, plaster Asbestos Asphalt shingles Carpets, linoleum Dirt, soiling, stones Drywall lining Fibre glass, insulation Metallic (ferrous and non ferrous) compounds Plastic compounds Paper, cardboard, tar paper, wall papers

Creosote Waterborne / organic preservatives Waxes, oils Paints, lacquers Glues, adhesives Fire retardants Water

References: Falk 1997, Fehrs 1996, Marutzky 1996 and 1997, Skog and Rosen 1997


If these wood residues are to be used as composting feedstocks these contaminants must be removed physically, e.g. by screening before or after composting, or must be broken down by the composting process. The resultant compost must be of beneficial use and must not result in negative effects upon the environment, e.g. inhibition of plant growth, and must also be aesthetically acceptable to the market place. Composite wood residues can be generated from recently produced wood products using modern adhesives and other chemicals. Wood residues may also come from older sources of wood containing a different range of chemicals, for example, lead-based paints3 or other chemicals which are no longer used. The effects of all of these chemicals must be considered in choosing to compost these feedstocks. The presence of plastic components in waste wood, e.g. melamine facing or as recycled wood fibres combined with plastic components, also must be considered by the composter. The effect on the end product may be one of aesthetics, i.e. visual appearance of plastic contaminants. These plastics may be prevented from entering the composting process by not allowing the input of plastic-coated feedstocks4

5, or the shredded plastic may be removed from the finished product by air separation methods6.

3.3 Types of wood residues Apart from residues produced from virgin hardwoods and softwoods by forest harvesting and primary processing, residues are also obtained from secondary processes, e.g. furniture construction7 8and from construction and demolition activities. These other sources may consist of virgin wood, painted wood or composite wood products. A number of reviews have been carried out on the composting of composite wood products9 10. There are many forms of wood composites,11 divided into three main types detailed into the section below. 3.3.1 Layered composites These can be used to produce both sections and sheets. Glulam (glued laminated timber) Formed by gluing together a series of small sections of timber to form large cross-section structural members of long length. LVL (laminated veneer lumber) Formed from thin sheets of wood peeled from the log (in a similar manner, but thicker than plywood veneers), which are glued together to provide the required thickness, and then cut into structural sized sections. Plywood Formed from thin sheets of wood (veneers) bonded together, most frequently with synthetic glues. The grain of the wood in the different veneers is normally arranged at right angles to each other. 3.3.2 Particle composites These can be further divided into four main types. The products are fabricated either from (a) small fragments of wood produced by cutting or mechanical fracture of timber (parallel strand lumber, particle boards, oriented strand board), or (b) long, thin, thread-like, strands of woodshavings (wood wool). PSL (parallel strand lumber) This is made from long strands of dried timber oriented with the grain parallel and glued together under heat and pressure into a continuous block which is cut into standard structural lengths. Particleboards (e.g. chipboard) Chipboard is made from wood chips produced by mechanically fracturing wood, such as forest thinnings and industrial wood waste, into small fragments. After drying, the graded chips are mixed with resin and formed into boards by curing in a heated press.


OSB (oriented strand board) This is made from strands of wood aligned in layers throughout the thickness of the board, the strands having a length of at least twice their width. This produces a cross-ply effect, emulating plywood with similar strength and stiffness. Woodwool Woodwool slabs are made from long strands of wood shavings, tangled, coated in cement and lightly compressed together. They have an open texture, and are very permeable to water vapour and are moisture absorbent 3.3.3 Fibre composites Fibreboards These are produced from chips of wood which are reduced to a pulp by mechanical or pressure heating methods. The pulp is mixed with water and other additives, formed on a flat surface and pressed at high temperature. There are three basic types of boards, differentiated by their increasing density insulation board, medium board and hardboard. Insulation board Insulation board differs from other fibreboards in that it is manufactured by only a wet process using resin glue. They have lighter density than medium or hard boards, and a smaller fibres compared to MDF or hardboards made in a dry process MDF (medium density fibreboard) This is manufactured by a dry or wet process using resin glue. The homogeneous cross section and smooth faces of MDF give high quality surfaces that are ideal for painting.

Hardboard

This type of fibreboard is manufactured using a wet or dry process. It differs from MDF and insulation board, having a greater density, although the fibre size is similar to MDF.

WASTE CARDBOARD Most cardboard wastes can be composted. However, care has to be taken with the source of the cardboard, physical and chemical contaminants, and printing inks. In the UK, cardboard is mainly used as a packaging material, especially within the manufacturing and retail industries. Cardboard residues can be obtained for composting as cardboard manufacturers waste, commercial packaging waste, through kerbside collection, or collection at Civic Amenity Sites. As of 2003/04, 32% of UK Local Authorities allowed the co-collection of cardboard in their kerbside collection schemes.12


3.4 Waste cardboard contaminants Waste cardboard may contain a number of physical and chemical contaminants13 such as: • Staples; • Adhesives (may contain boron); • Tape (paper or plastic); • Plastic liners; • Waxes (may contain volatile and polycyclic aromatic hydrocarbons); • Colouring agents; • Bonding agents; • Printing ink; • Polystyrene; and • The original contents of the packaging, e.g. food. Staples are not normally removed from the cardboard before composting, but those associated with large cardboard fraction may be during the screening of finished compost product. Plastic tape, polystyrene, and plastic liners may be removed before shredding or may be screened out after composting is completed. Ink used for printing on cardboard is chemically much more complicated than is often appreciated. Ink is defined as a colloidal system of fine synthetic pigment particles dispersed in a solvent. The pigment may be coloured, or not, and the solvent may be aqueous or organic14. There is an increasing move towards the use of water as a solvent. Inks used for printing paper and cardboard are dispersions of synthetic organic pigments (rather than dyes as in writing ink) in a bonding agent system built up essentially of resins, vegetable oils and high-boiling-point mineral oil products15. The proportion of mineral oil material in the ink ranges between 20 to 30%. Printing ink may include16: • pH modifiers; • humectants to retard premature drying; • polymeric resins to impart binding; • defoamer/antifoaming agents to regulate foam efficiency; • wetting agents (e.g. surfactants) to control surface tension properties; • fillers or extenders (clays) to reduce costs; • biocides to inhibit fungal and bacterial growth; and • thickeners to control the rate of ink application. Printing ink pigments are insoluble and may be inorganic or organic. Most white inks contain titanium dioxide as the pigment. However, in order to reduce the levels of heavy metals in printing inks, many of the inorganic pigments such as chrome yellow, molybdenum orange and cadmium red have been replaced by organic pigments. Also, carbon black is now the pigment in almost all black inks.

3.5 Types of waste cardboard There are two main types of waste cardboard in the UK, normally obtained as packaging waste. Both types can be composted. • Corrugated cardboard – consisting of two flat sheets of cardboard with a ruffled layer between the

two. Used frequently as a packaging material which may have printing ink applied; and • Flat cardboard (paperboard) – consisting of a single flat sheet of cardboard. Used in cereal boxes,

shoe boxes etc. and often coated and well as printed.


COMPOSTING IN THE UK The composting of organic wastes in the UK is a rapidly expanding industry. This growth has been followed and reported upon in a number of surveys carried out by The Composting Association17 18 19 20. The 2004/05 survey showed that c. 2.67 million tonnes of organic wastes were composted in that period . The report also states the 16% of local authorities accepted cardboard with green wastes in their kerbside collections, and 16% accepted cardboard mixed with kerbside collected green waste and kitchen waste (10% up on the previous survey for 2003/4). Overall, the breakdown of wastes composting during the period of the latest report (2003/04) is summarised in Table 4:

Table 4 Organic wastes composted in the UK 2003/0412

Waste type Input (‘000 tonnes)

Percentage of Total

Municipal Household 2,178 81.5 Municipal Non-Household 63 2.4 Commercial (Non-Household) Commercial landscape 135 5.0 Forestry 57 2.2 Food processing 93 3.5 Food retailers 2 0.1 Paper and card 2 0.1 Other organic by-products 5.2 Totals 2672 100

3.6 Legislative drivers for the UK composting industry To a great extent the growth of the industry has been driven by changes in legislation. The introduction of the EU Landfill Directive 199921 included mandatory targets for the reduction in the amount of biodegradable waste going to landfill. For the UK the quantity of biodegradable waste (including wood) that can be disposed of to landfill must be reduced as follows: • 75% of the amount produced in 1995, by 2010; • 50% of the amount produced in 1995, by 2013; and • 35% of the amount produced in 1995, by 2020. The Waste Strategy 200022 provided guidance on the UK Government’s views on the way that biodegradable waste (including wood) should be handled and produced the following targets for the recycling and composting of household waste: • To recycle or compost at least 25% of household waste by 2005; • To recycle or compost at least 30% of household waste by 2010; and • To recycle or compost at least 33% of household waste by 2015. Since then each Nation within the UK has developed its own separate strategy, setting more challenging targets. The reduction in biodegradable municipal waste landfilled is driven primarily by economic incentives under the Landfill Allowance Trading Scheme, legislated by The Waste and Emissions Trading (WET) Act 2003.23

3.7 The composting process Composting can be defined as “the breakdown of organic wastes by micro-organisms, in the presence of air, to produce water, carbon dioxide, heat, and a more stabilised, pasteurised organic material (compost)”. All composting technologies, whether simple or sophisticated, open or contained, share a number of basic characteristics. In composting, a wide range of bacteria, actinomycetes, and fungi act upon organic feedstocks, in the presence of air (oxygen) and water to carry out a number of chemical changes. Some of the lipids and carbohydrates in the feedstocks are broken down via a number of intermediates into carbon dioxide and water. At the same time, energy is released in the form of heat raising the temperature of the composting mass. Some of the proteins and amino acids are also broken and ammonia may be released. The more resistant components in the organic waste (ash, lignin, and


cellulose) contribute to the final compost product, although some of the cellulose and lignin is broken down. In the process of carrying out the above chemical changes, particular micro-organisms (bacteria, actinomycetes and fungi) increase in number in the composting material. These newly produced micro-organisms contribute to the composting process and bring about further breakdown with increased microbial production. Over the period of composting, different varieties of micro-organisms flourish at different stages. Some of these die and become part of the organic waste being broken down. The first stage of a composting process is referred to as the pre-composting stage and normally involves shredding the wastes to a small particle size (c. 2-5 cm). There are a number of different shredding techniques available and a variety of shredders24,25. Some shredders operate at low speed and high-torque, while others operate at high speed and have a lower torque. Some machines have one or more rotating shafts and sets of cutting disks. Others use contra-rotating shafts that pull the material into contact with the cutting disks. Shredded wood tends to consist of a wide variety of particle sizes, including some that are so big that they will remain intact through even an extended composting process. Typically, oversize material is returned to the composting process. Dry, firm wastes such as wood waste may also be taken through a grinder rather than a shredder. Grinders can be of the flat-bed variety or take the form of a tub-grinder 26. In each case the wood waste is broken down at high speed by a series of hammermills. Some systems operate a two stage or multi-stage shredding/grinding process resulting in the production of material with a very even and reproducible particle size and with little or no oversize material present 27. The porosity of the composting mixture is very important in determining how easily air can penetrate the composting mass in order to ensure aerobic composting conditions. The addition of shredded wood to other wastes normally improves the porosity of the mixture. Shredding is normally followed by mixing the wastes thoroughly to produce an homogeneous feedstock, and by addition of water, if necessary, to optimise the moisture of the mix. The optimum moisture of a composting mixture involving wood waste will depend very much upon the ability of the mixture to hold water without producing excessive leachate. It is often considered advantageous to pre-wet the shredded wood before mixing it with the other components. The stage may also be used to add nitrogen directly to the wood prior to composting in the form of a urea solution.28 The pre-composting stage is normally carried out over a period of a single day. The next stage of the composting process is variously called the first stage, rapid stage or high-temperature stage, during which the temperature of the composting mixture can rise to between 45oC and 75oC (when pasteurisation is achieved). Much of the initial breakdown of the waste occurs at this point. At the end of this stage the material may optionally be screened (before composting is continued), to remove oversized particles that can be returned to the start of the process, re-shredded or disposed. This stage may last between 3 days and a number of weeks, depending upon the type of composting technology employed. It may be carried out in a windrow or within an enclosed vessel. The next stage, referred to as conditioning, second stage or lower temperature stage, takes place at a lower temperature (45-50°C). This temperature may be reached naturally, as the high-temperature stage comes to an end, or it may be brought about by the composter increasing the supply of fresh air to the compost and thereby cooling it. It may last from several days to a number of weeks depending upon the composting technology used and the type of compost being made. The next stage of composting known as the curing or maturation stage, takes place at even lower temperatures, between ambient and 45°C. Further chemical reactions occur during this stage to produce mature and stable compost, for example the conversion of ammonium to nitrate. Depending upon which type of compost is being made, this stage may be missed out. Some applications may be able to use compost directly after the conditioning stage, while others may require very stable compost that has been allowed to mature for several months. A number of approaches have been taken to defining the end-point of the composting process and in determining the degree of stability of the compost product29 30. The end point of a composting process is ultimately determined by the required specification of the compost product. Some applications of waste-derived composts require a highly stabilised product. This requirement will apply, for example, when the composted material is to be part of a formulation of a growing medium that may be supplied and stored in plastic bags. Other applications, for example as a bulk soil improver in agriculture, will require a less demanding level of stabilisation.


The final stage of composting is referred to as the post-composting stage. This often involves screening the compost into range of products of varying particle size, where oversized particles may be removed and put back into the composting process or disposed.

3.8 Composting technologies 31 There is no single method of composting that is correct or optimal under all circumstances. The composting technology chosen by a composter will always depend upon the waste being processed, the product being made, and a number of other practical and financial considerations. The available technologies range from the very simple to the very sophisticated. Composting technologies can be divided into two basic categories: those in which the composting process is carried out within some form of container, and those that are not. Composting technologies may be further divided according to whether the composting material is moved or not, if forced air is supplied or not, and whether the composting process is carried out on a continuous or batch basis. Wood waste and cardboard waste can be composted using any of the composting technologies listed, as long as the wastes and properly comminuted and form part of a mixture of feedstocks optimised for composting. In the case of wood and cardboard, this means the addition of moisture and a source of nitrogen.

Figure 3 Classification of composting technologies

Composting Technologies

Contained systems

Open systems

Windrow Aerated static pile

Vertical flow(Continuous)

Non- flow(Batch)

Horizontal flow

(Continuous)

Silos Rotary drums

Agitated bins

(Circular)

Agitated bays(Rectangular)

Continuous tunnels

Fixed batch tunnels

Mobile batch tunnels

Composting technology is still in a process of development and a considerable number of new suppliers have entered the market. However, these new technologies can be incorporated into the above classification.

COMPOSTING WOOD WASTES In a survey carried out in 199832 it was estimated that disposal of the 799,000 tonnes per annum of wood not being salvaged did not involve any going into the composting industry. In a study published in 200333 composting was identified as a disposal option for wood waste from the furniture industry by 6.9% of companies and this accounted for 11% of the wood waste produced. Another survey report34 indicated that no more than 10% of wood waste was sent for final disposal to landfill, and that most wood waste producers had their wood waste collected by third parties for recycling or composting, while many were able to reuse and recycle a proportion of the waste, for example as fuel. In this report 9% of the wood waste generated by wood recyclers and processors was


sent off site for composting. The figure for forestry and arboriculture was 17%. The report also identified the problem that some treated wood waste was not suitable for composting. A WRAP report 35 on the use of treated wood waste looked at the options available for the composting of this type of material. Composting was put forward as the Best Practicable Environmental Option only for treated wood waste derived from packaging. Treated wood wastes from other sources, e.g. construction wastes and municipal solid waste were held to be unsuitable for composting because of the contamination of the composted products. It is the purpose of the present study to look in detail at the feasibility of producing useful composts from wood-based materials from sources other than packaging. Other WRAP reports36 37 looked in detail at the feedstock specifications for a number of different wood applications including composting. These reports pointed out the usefulness of wood wastes in reducing the moisture, and increasing the C:N ratio, of other wet wastes intended for composting such as biosolids and catering wastes. The addition of wood could also improve their structure to allow adequate aeration. A WRAP report38 pointed out the value of composting wood wastes as part of a soil remediation scheme and also as a method of making artificial top soils, e.g. using wood chips. The requirement to minimise contamination with glass and other inerts was noted. Options for using composting as one method of increasing the recovery of panelboard waste is discussed in a recent WRAP report39 . This report identified the need to investigate co-composting this material with other wastes to speed up the process, to test and demonstrate the quality of the resultant compost, and to explore end uses. This report stated that as far as the furniture industry is concerned, 163,814 tonnes of waste (c. 260,000 m3) from furniture processing are being used for composting or animal bedding. The report concludes that most of this is wood waste and that the vast majority of panel waste is currently sent to landfill or burned without energy recovery. The report goes on to describe two UK companies who currently compost panel board or use composted particle board prepared by another company. Between 6,000 and 12,000 tonnes a year of composted material are utilised. The composting company proposed that the urea in the urea formaldehyde-bonded particle board, composted on its own only with the addition of water, acted as a ‘catalyst’ for the composting process. It was recognised that co-composting this type of waste with green waste would accelerate the process. The problem of this type of material being coated was recognised. This would either have to be removed at the screening stage after composting, or the product would have to be sold into markets where the presence of coating was acceptable. The report also presents a ‘Capability Matrix’ in which an assessment is made of the relative merits of a number of recovery options. The cost of composting wood waste has been estimated in one report40 as ranging from £10- £20/tonne, with additional costs, including shredding, packaging and transport, adding a further £7-£52/tonne depending upon the volume and manner by which the resultant compost is sold and supplied. The higher costs refer to compost packaged and transported in small bags into the retail market. This market commands higher prices than the bulk market but is also very difficult to penetrate and expensive to exploit. In essence, the cost of composting wood waste, and marketing the resultant compost, should not inherently be any greater than the cost of composting any other form of solid organic waste. A survey of cost of processing municipal waste within the EU41 estimated the cost of windrow composting to be c. £15/tonne and in-vessel composting c. £30/tonne. These figures would also apply to composting operations in which shredded wood was included. However, composting costs are very site specific and will vary according to a number of parameters, including42: • Cost and purchase or lease the associated area required; • The composting technology (in-vessel systems tend to have a smaller footprint than windrow

systems, but windrow composting is often used after in-vessel composting as a secondary composting stage);

• The percentage of site capacity utilised (processing costs can spiral if the site has a low utilisation rate);

• Efficiency of getting completed composting off site (failure to do this may restrict the intake of feedstock and increase unit processing costs);

• Nature of final product (higher quality product requires higher processing costs than that required by the production of a restoration or agricultural product); and

• The percentage of rejects that have to be landfilled Whether a particular wood residue is used in composting depends very much on the quality and quantity of the wood residue and the type and amount of contaminant present, including bonding agents, preservatives, paints, and other chemicals. Supply issues also influence the likely success of reuse or recycling options. These include factors such as:


• continuity of supply in sufficient volumes; • absence of contamination; • marketability of products manufactured ; • lack of new disposal problems to be created; and • economical viability. The composting of furniture waste has been reported in a detailed study43 that shows the significant benefits of using composting to process waste from the UK furniture manufacturing industry. The composting of plywood and sawmill residue is covered in a number of reports44 . The process of co-composting wood wastes with other wastes follows the same general principles of composting outlined earlier. However, special consideration has to be given to the fact that wood is typically hard, dense, dry and has a very high C:N (carbon:nitrogen) ratio. Most wastes are comminuted (shredded/ground) before composting in order to increase the surface area on which micro-organisms can act and to produce a more uniform mixture. This process is particularly important for material such as wood which are inherently difficult to break down. There are many different systems used to shred wood and other materials and many different suppliers of equipment.45 46 47 There are a number of basic parameters that a composter must control and optimise in order to compost wood waste effectively. These include oxygen, moisture, temperature and the C:N ratio of the feedstock mixture. This last parameter is controlled by mixing the wood waste (which has a typical C:N of between 300:1 and 700:1) with wastes of much lower C:N ratio, such as manures, biosolids (sewage sludge), grass clippings and food waste, in order to bring the C:N of the mixture to near 30:1 which is the optimum for a composting process 33. FIRA has carried out composting trials with wood dust.48 Wood is difficult to compost49 , compared to other, softer feedstocks such as green waste, grass and biosolids, because of the high levels of lignin present that are resistant to rapid microbial degradation. The presence of preservatives and biocides in the wood may further limit or slow down degradation. Changes in the issues affecting preservative suppliers for treated wood have recently been summarised.50 This report summarises the European legislation covering the use of wood preservatives and outlines the considerable changes that have taken place in the market place over the last 20 years. The use of traditional preservatives such as chromated-copper-arsenate, creosote and pentachlorophenol are now severely restricted or banned. Preservatives currently used fall into three categories: • Water-based organic biocide preservatives such as triazoles combined with synthetic pyrethroids; • Copper-chromium based preservatives such as chromated-copper-boron, chromated-copper and

chromated-copper-phosphate; and • Copper in conjunction with an organic biocide, such as TANALITH E. However, it should be recognised that some treated wood made available for composting could contain the older preservatives that are no longer used such as dieldrin and lindane. The fate of some of these older chemical in the composting process are discussed in a review on the persistence and degradation of pesticides in composting51 and in an article dealing with dieldrin in particular 52 It is normally possible to introduce wood waste into existing composting operations as long the inclusion rate is not too high and basic limitations regarding C:N, moisture and other parameters are followed. It is vital that C:N ratios are reduced to about 30:153 54, that nitrogen comes into contact with the wood, and that the wood particles are moistened. Poorly composted wood may cause phytotoxic reactions if the resultant compost is used as a soil improver55. During composting and maturation phytotoxic compounds should be broken down completely.56 The manufacture of composite wood products requires the use of bonding resins such as: • urea-formaldehyde (UF); • melamine-formaldehyde (MF); • melamine-urea-formaldehyde (MUF); • phenol-formaldehyde (PF); and • isocyanates.


In addition, the composite products may be treated with preservatives (to prevent microbial degradation or attack by insects), waxes or other chemicals (to repel water)57, or chemicals to retard fire58. These chemicals may be added separately or combined with the glues or resins. A number of these additives have health and safety implications.59 60. Techniques have been developed to identify61, sample and analyse these chemicals62. The effect of the composting process on some of the chemicals used in the treatment of wood is an important consideration for composters and has received considerable attention. A number of reviews have looked at the use, and composting fate, of biocides added to composite wood products63 64 65. These show that most biocides do not cause contamination problems with the compost product as they are degraded during composting. One study65 showed that composite wood materials, such as chipboard, plywood and laminates, were degraded by the composting process and the resultant composts displayed no biotoxic effects. Another study63 showed mechanisms by which composting can break down the types of chemicals involved. These mechanisms include mineralisation, abiotic transformations, adsorption, leaching, humification and volatilisation. Although most chemicals were quickly degraded, some organochlorine compounds (such as dieldrin and DDT) were difficult to degrade. This result indicates that great care has to be taken in processing old wood that might have been treated with such chemicals and that compost produced from treated wood should be regularly tested for chemical contamination. A wide ranging study66 on the effect of composting on pesticides, preservatives, PCBs, chlorophenols and PAHs has been carried at a laboratory scale. This work showed a wide variety in the response of these chemicals to composting. 2,4–dintrophenol and diazanon are rapidly broken down whereas atrazine and PCB breakdown was limited. Great care should be taken in taking data generated at the laboratory scale and assuming that similar results will be obtained at the commercial scale. The health risks involved in composting are well documented, although a number of gaps in our knowledge still exist67. The risks inherent in the composting of untreated wood do not seem to carry any specific additional risks. However, because of the additional chemicals involved, the composting of treated wood wastes deserves attention. During the initial shredding process, during composting itself, and during the screening and handling of processed materials there are opportunities for volatile chemicals to be produced and released. There is also the potential for some of these added chemicals to survive the composting process. The composting of a number of specific chemicals associated with wood residues have been studied in some depth.

3.9 Formaldehyde A report published in 197968 suggested that the rate of emission of formaldehyde from treated wood can, especially in an enclosed environment, produce enough emissions of formaldehyde to cause eye and respiratory irritation. This fact should be considered when shredding treated wood and in controlling the process air from the composting process. Adequate ventilation and/or suitable scrubbing of process air should be considered. Testing for formaldehyde presence in the working environment should be carried out if thought necessary. In a report69 on a six month composting study, sawdust from machined softwood plywood bonded with phenol-formaldehyde resin was amended with chicken manure, cow manure, horse manure, cotton gin trash and inorganic fertilizer. The amended sawdust was composted for 180 days. Compost samples were tested for weight loss and for toxicity. Greenhouse tests were conducted on corn, soybeans and cotton by amending potting soil with 25% of each compost sample. All treatments showed a significant decrease in toxicity by day 180, maintained a neutral pH throughout the study (with the exception of the horse manure treatment), and showed a significant reduction in weight. Dry weights of crop plants from the greenhouse study showed no significant difference between potting soil only and potting soil mixed with composted sawdust amended with chicken manure. All other treatments were comparable with the chicken manure, with the exception of the cotton gin trash treatment. The authors concludes that composting PF-bonded sawdust can produce an acceptable soil amendment in a 180-day period. A subsequent report70 evaluated the compostability of MDF sawdust in a simulated MSW. Composting was conducted over a 10-day period at 45ºC. and 55oC. Simulated MSW was amended with 2.5% and 5.0% MDF sawdust by weight. Samples of the substrate were collected every two days to determine the degradation rate of formaldehyde. Dry matter loss over 10 days was less than 14% for the mesophilic phase and 13% for the thermophilic phase. After 10 days, formaldehyde was reduced by over 90% in


both mesophilic and thermophilic phases in fixed-temperature conditions (at 2.5% MDF), by about 80% in biodegradation tests (independent of temperature and MDF concentration), and by about 66% under adiabatic conditions (simulating outdoors composting). No gaseous formaldehyde emissions were detected in either phase. In commenting on these two reports, a further report71 discussed the demand for engineered wood products like plywood, MDF, and OSB and the resultant waste streams that are generated from these materials. The main concern about composting these wood wastes has been the presence of formaldehyde from the urea-formaldehyde or phenol-formaldehyde glues used in the manufacturing process of these products. The author concluded that the two earlier studies showed that engineered wood wastes may be suitable for use as a composting carbon source without concern about formaldehyde resins and glues. A recent US study72 has reviewed the potential environmental risks of onsite re-use of ground engineered wood wastes from residential construction. This report refers to a 1994 study73 in which sawdust from urea-formaldehyde bonded pallets decomposed very slowly unless additional nitrogen was added. It was concluded that much of the 4% nitrogen present in the sawdust was unavailable for composting in the short term (14 days). The study found that emissions of formaldehyde to air varied from very low to undetectable. Another study looked at wood waste from furniture production containing urea-formaldehyde74. It was found that nitrogen was released from the urea-formaldehyde after 45 days composting with fermentation biomass. A study looking at the composting of plywood products containing urea-formaldehyde75 found that these products can decompose slowly even without added nitrogen but that they would decompose quicker if animal manures or inorganic nitrogen were added. Six month old compost made from this material was tested in greenhouses with soybeans, cotton and corn and was found to have no toxic effects on these crops.

3.10 PAH The composting of wood containing PAHs (phenanthrene and pyrene) has been studied under laboratory conditions76. Contaminated wood from industrial applications was studied along with untreated wood to which the PAHs were added in the laboratory. The wood was soaked in pig manure before being composted. After 61 days composting in Dewar vessels, the PAH concentrations were reduced from 1000 mg/kg of each PAH to 26 mg phenanthrene and 83 mg of pyrene/kg. Both industrially contaminated and laboratory contaminated wood reacted positively but the industrially wood responded slower.

COMPOSTING OF WASTE CARDBOARD Cardboard is routinely composted as a component in kerbside collected green waste/kitchen waste, although some local authorities exclude cardboard on the grounds that it is ‘difficult’ to compost and may collect it separately for recycling. A number of studies have looked at the implications of adding cardboard to a composting mixture or of composting cardboard per se77. One study78 looked at the disintegration of Biopol-coated cardboard and other packaging materials within a composting system. Direct addition of the cardboard to the composting windrow was not found to have any detrimental effect on the process and the compost produced showed no toxicity on plant growth tests with barley and radish seeds. The composting of multilayer cardboard boxes (Tetra Brik Aseptic (TBA)) has been examined in an US study.79 The aluminium and polythene sections of the TBA remained intact throughout the composting process but the cardboard component was successfully broken down. Heavy metal levels were acceptably low. The composting of waxed corrugated cardboard has also been examined80. It was found possible to compost this type of material very successfully by combining it with broiler or hen manure. The finished compost could be marketed into horticulture as well as agriculture. A number of technical studies have been carried out on how to compost cardboard efficiently. The disintegration of Biopol-coated cardboard, polylactide fabric and film was studied81 by adding the material directly to the compost pile, placing them in the pile in nylon bags, or in steel frames. Adding the materials directly to the compost pile had no detrimental effect on the composting process. The use


of steel frames proved to be good a method for testing samples such as packaging materials. Both polylactide samples and Biopol-coated cardboard degraded completely in the steel frames. The compost produced from the samples showed no toxicity in the plant growth test with barley and radish seeds performed at the end of the experiment. In 1993 the Clean Washington Center (CWC) carried out a series of seven trials co-composting produce waste and waxed cardboard waste from the grocery industry in varying proportions with green waste82. The ratio of cardboard to the other wastes varied from 1:5 to 1:10 (v/v). The study showed that the addition of cardboard had no deleterious effect upon the composting process when used up to an inclusion rate of 15% (v/v). Heavy metals levels in the cardboard and the finished compost were significantly below the maximum allowed standards. The wax used in the production of the waxed cardboard was produced from the distillation of crude oil. One sample of the waxed cardboard was therefore analyzed for volatile organic aromatic compounds. None of the compounds analyzed for was detected. Waxed corrugated cardboard was shown to be compostable in a 1998 US study83. Shredded cardboard was mixed with two forms of poultry manure and at two different inclusion rates. It was found that thorough mixing and moisture levels above 50% were needed in order to compost the cardboard efficiently. Heavy metals in the final compost were much lower than that described in the 1993 CWC study. This was held to be because the CWC study used cardboard packaging from the grocery industry that had much more printing ink and printed labels on it. A 1997 study84 looked at the effect of different inclusion rates (by volume) of waxed corrugate cardboard (0%, 25%, 50%) in a windrow composting operation (over 12-16 weeks) using spent mushroom compost (50%) and pulverised wood waste (50%, 25% and 0%) as the other feedstocks. Supplemental nitrogen was added to some trials in the form of poultry manure and/or soybean processing wastes. During the first 8-10 weeks composts containing 50% cardboard reached and maintained the highest temperatures but then cooled the most rapidly. The paraffin wax in the cardboard was degraded by 95%. Electrical conductivity and levels of phenols were highest in compost made from feedstock containing 50% cardboard. All the mixtures produced usable composts.

3.11 Markets for composts containing composted wood or cardboard

A number of extensive reviews have been carried out on applications and markets for composts derived from various wood wastes.87 A number of studies have also been undertaken to identify and quantify markets for recycled wood waste including composting. The quality requirements of wood feedstock for composting to produce mulches and soil conditioners are that it should be clean, mixed wood with not too many fines85. Wood waste, such as wood chips, shavings, off-cuts (suitably comminuted), and sawdust, can also be used as a component in bioremediation using windrow composting86 technology or in engineered biopiling (aerated windrows)85 87

. The latter technique involves the use of forced aeration. The composting of composite wood residuals can be economically viable. The compost produced from these feedstocks (or their mixes) can be used for the production of a variety of end-products. Given that composite wood composts comply with standards for soil conditioners and mulches, composite wood-based composts should attract similar markets to other composts made from more traditional feedstocks. The manufacture of compost can be targeted towards low and high value markets depending upon the composting process and quality of feedstock used. High value products require quality feedstock, good screening processes for the removal of physical contaminants, and effective size reduction and composting procedures. Monitoring of compost quality and chemical composition during the composting process is necessary to maintain standards and also to avoid possible contamination issues associated with the resins and preservatives used in composite wood products. Some examples of end-products and applications for compost include soil conditioners, mulches, potting mixes and soils for landscaping and garden use. Composted wood fibre can form a component of commercial horticultural products88 89. Compost that has been manufactured from lower quality feedstocks, comprising higher physical and chemical contaminant levels can be used for the bioremediation of degraded areas. For these end-products, the manufacturing process is less extensive, giving reduced production costs, and product prices that are markedly less than those for high quality products. Composts utilised in this way do not


require extensive screening, size-reduction or fully matured compost, as they are applied to areas (e.g. mine-site rehabilitation) to assist with the biological breakdown of hazardous organic chemicals. If cardboard is co-composted with green waste, or kerbside collected kitchen waste mixed with kerbside collected green waste, at proportions less than 10% (v/v) the resultant compost should not be significantly different from composts made without the addition of cardboard90 and should attract similar markets. The upper inclusion rate for cardboard is a subject of the present WRAP study.


3.12 Quality control and standards for composting wood wastes and cardboard

The most important standard for composts made from any source-separated organic wastes in the UK is the BSI PAS 10091 although other standards are also relevant. Other standards include composting specifications for the landscaping industry, top soil manufacture, reclaiming disturbed land for forestry and in land reclamation, and are summarised in a recent WRAP report 38.

3.13 Influence of the literature survey upon the structure of the composting trials

The results of the literature survey on the composting of wood wastes and waste cardboard have influenced the design of the composting trials associated with this project in the following areas: • It is clear that much of the compositional and analytical work reported in the literature has been

carried out on small scale or even bench top composting trials. It is often very difficult to extrapolate the results of such trials to commercial scale. There is a demonstrable need for the composting trials to be carried out at a full commercial scale;

• Where composting was carried out at a scale approaching a commercial scale, the composting process consisted of the turned windrow method with little control over the composting environment. This emphasised the importance of using a highly controlled and documented composting process. The use of windrow composting and in-vessel composting allows the project to cover both ends of the scale of composting sophistication;

• Adding shredded wood to a composting mixture both reduces available moisture and increases the C:N ratio of the mixture. Both of these effects will result in a slowing down of the composting process;

• In order to avoid these problems and to produce a feedstock mixture for the trials that composts at or near optimum conditions, there is a clear upper limit to the proportion of wood waste and cardboard waste that can be used without slowing down the process;

• There is also a strong argument for adding water and nitrogen directly to the shredded wood before mixing with the other feedstock components; and

• A survey of the analytical processes detailed in published literature revealed a number of gaps and allowed an identification of the analyses to be carried out by the project.

3.14 Conclusions

It is clear that while the composting of wood wastes and cardboard wastes can both be carried out successfully, there are a number of important factors that need to be considered. • Care has to be taken to understand the origin of the feedstocks and thereby the potential for

contamination; • The presence of any physical contaminants in the composting mixture should be minimised, if

possible, before composting begins. Alternatively, a screening process after composting is completed should be used to remove any remaining physical contaminants;

• The presence of any chemical contaminants in the feedstock should be determined either by a knowledge of the material itself and its origin, or by the direct analysis of the feedstock;

• The wood or cardboard feedstock should be comminuted to ensure that the two feedstocks are efficiently composted and will not reduce the value of the end product;

• The initial composting mixture should be formulated to ensure that there is adequate moisture present and that the starting C:N of the feedstock is c. 30:1;

• Composting should be carried out as efficiently as possible, perhaps using an in-vessel system. • Composting should be continued until biotoxicity tests show that the compost has no deleterious

effects upon plant growth; • Composting should be carried out according to an acceptable standard such as PAS 100; and • Further work is needed to give confidence to commercial composters, and users of their composts,

that wood and cardboard can be successfully composted in a routine way.


4 Operator Survey

A survey was carried out to establish the current state of wood waste composting during July/August 2005. The aims of the survey were to: • Establish the sources of cardboard and wood containing wastes, and the quantities that the sites

surveyed produced; • Determine the percentage of wood or cardboard included; • Identify the advantages/difficulties of composting wood or cardboard in terms of economics,

processing procedures and compost quality; and • Identify the end uses of the resultant material.

4.1 Methodology Fifteen compost operators were contacted to acquire a general overview of the state of wood and cardboard composting in the UK. The baseline questionnaire is attached in the appendix. The survey was aimed primarily at medium and large scale compost operators. Previous research by The Composting Association (2005) has indicated that small-scale operators focus primarily on green wastes, therefore it is unlikely that these operators would compost wood wastes.

4.2 Results The survey operators were categorised as follows: • operators composting wood wastes; • operators composting wood and cardboard wastes; • operators composting cardboard wastes; and • operators not composting wood or cardboard waste Within the above categorisation there were five companies that collected wood waste and sent it to wood re-processors, rather than composting, and two that no longer composted cardboard, although they had previously.

4.2.1 Types, quantities and sources of cardboard and wood containing wastes The wood waste received on site was categorised into a small number of rudimentary categories depending on the level of contamination either ‘clean, high grade’ or ‘contaminated, low grade’ material. This meant the survey was unable to identify the quantities of specific panel board types such as medium density fibreboard (MDF), orientated strand board (OSB) or chipboard. The majority of those questioned could not provide exact quantities of materials composted. Three operators stated the quantity of wood waste composted was 3-5,000, 2,000 and 5,000 tonnes per annum. One stated they collected 14,000 tonnes per annum but did not compost the majority. The material was sourced primarily from civic amenity sites, but was generally a mix of civic amenity and commercial sources. The composted cardboard was collected as part of a kerbside collection, so the quantities of cardboard collected could not be accurately established.


4.2.2 The percentage of wood and/or cardboard There was a very large variation in the proportion of wood or cardboard included in the composting process. The quantity of wood included ranged from the ‘almost insignificant’ inclusion of small wood fines to a mulch product, which was virtually 100% wood. Few producers were able to give any quantitative data. The best estimate provided was a 10-15% inclusion rate for wood wastes that was composted for use in land restoration. The sites which composted cardboard received the material as part of a kerbside green and/or kitchen waste collection. It was therefore difficult to establish an inclusion rate, given that the weights were not recorded separately. The percentage of cardboard varied from c. 10% in the summer to c. 75% in the winter. However, not all this material was composted with the excess being screened out at the end. 4.2.3 Feedstock preparation/pre-treatment The preparation of feedstock materials was fairly limited. The compost producers tended to use the machines that they already had on site to reduce the particle size. The material was often wetted thoroughly. This was an important part of composting both cardboard and wood, which tended to dry out quickly. 4.2.4 Advantages/difficulties of composting wood and cardboard The survey identified a number of advantages and disadvantages of composting cardboard and wood wastes in terms of • Processing procedures; • Time-scales; and • Economics. 4.2.5 Processing procedures Compost producers found the process of composting cardboard and wood wastes more challenging than composting green wastes alone. The main modification to the composting practice was increased wetting of the material. Some compost producers would only put wood fines through the composting process as there is more surface area to absorb moisture and they composted more readily. One producer used the waste wood composting process as a means of treating liquid wastes. The main processing advantage of composting card is that segregation of feedstock is not necessary. There were some difficulties with composting wood and cardboard. Reducing the particle size of wood leads to a large increase in dust emissions, and due to the dry nature of the wood and rapid heating there is an increased risk of fire. The main problem identified in both cardboard and wood waste composting was drying out. The cardboard was also difficult to shred and forms pulp when wetted. Some compost producers also found that composting cardboard was difficult in the winter. Two producers stated that the percentage of cardboard collected in the winter was 70% or greater. The high inclusion rate may affect the ability to meet ABPR temperature requirements. 4.2.6 Timescales The composting of card and wood was carried out as for green waste composting. Composting was carried out depending on the degree of stability required for the end purpose. 4.2.7 Economics The economics of composting wood waste was the key benefit identified by the respondents. Although, no respondents divulged the exact gate fee obtained, a higher fee than green waste was obtained in some circumstances. The prices obtained for the resultant compost varied markedly from £0-26 per tonne. Generally operators only including a small quantity of wood wastes where able to obtain a price similar to composts green waste alone. 4.2.8 Compost quality Compost quality was described mainly in terms of aesthetics. The main factor influencing the quality was the inclusion rate of the wood or cardboard waste. Compost producers were not generally aiming


to produce the compost to an independent quality standard like PAS 100. This was not perceived as an issue for most sites as wood was generally included in compost made for lower value markets. One site did meet PAS 100 for their cardboard composting process and another was in the process of obtaining the specification. 4.2.9 Contaminants The composters questioned were only able to identify visual or physical contamination. The contamination was mainly due to difficulties in separating the waste, as wood waste may contain hinges, nails, glass etc. Some producers stated that allowing cardboard in the kerbside collection also resulted in an increase in other unwanted packaging such as plastics. The majority of compost producers avoided composting any wood that was contaminated with paints or preservatives. 4.2.10 End uses The end use of the composted material varied. The main products produced were either mulches or soil conditioners used primarily in land restoration, agriculture or landfill restoration. The outlet depended on a variety of factors including the rate at the quantity of wood or card included and the site’s overall marketing strategy. Specifically, the availability of a landfill restoration outlet enabled producers to incorporate more wood waste.

4.3 Summary of Telephone Interviews

The results of the fifteen telephone interviews are summarised in Table 5. All the sites interviewed were medium to large-scale compost producers, defined as those composting at least 10,000 tonnes per annum.

Table 5 Summary of telephone interviews

Producer Waste type, sources, quantities

Pre-treatment Inclusion rate Advantages/disadvantages Quality End use

1 Do not put waste wood through the composting process.

2 Do not put wood waste through the composting process.

3 Compost approximately 3-5,000 tonnes of wood wastes at two sites.

Do not alter composting practices.

No maximum inclusion – either incorporated with the oversize fraction or mixed with commercial waste.

Diverts lower grade material from landfill.

In house standards Land restoration




4 Experience of composting wood and card from a variety of sources.

Shredding / wetting.

No maximum inclusion - wood used as a bulking agent to amend food waste at a approximately 10-15% by weight inclusion rate. Wood waste inclusion could be as high as 25% by weight if the facility is processing biosolids.

Economic value of the product £12-26.

Do not generally recommend that local authorities collect card. The proportion of card in the winter can be as high as 70% of the mix, and therefore can affect the ability to meet ABPR temperature requirements. Therefore a high nitrogen / moisture source needs to be added which then affects the capacity and sizing.

Chipped clean wood is beneficial in providing porosity but the benefits of card are less clear. Card should only be added if the facility is processing very wet with a high nitrogen content.

Exclusion of any wood containing preservatives, soft boards, laminated with plastic or painted.

Landscaping and hobby gardeners.

5 2,000 tonnes civic amenity site wood wastes per annum.

Plan to compost cardboard in the near future.

Shredding / Wetting (as for green waste).

Not defined No problems composting wood waste compared to green waste. They plan to compost card in the future, but are aware of potential problems that other sites are experiencing.

Retention time is longer than green waste.

In house standards.

Landfill restoration




6 Clean mixed wood (avoid contaminants) and cardboard.

Shredding / wetting.

Not defined Wood composts well.

Cardboard can be difficult and lead to more contamination.

In the process of obtaining PAS 100.

Landscaping and landfill restoration.

7 The majority of the wood collected is not composted but sent to wood recyclers or used for fuel.

Usually only very small, fine particles are composted.

Very low Obtains value of £6-7 per tonne of compost.

Higher gate fee than green waste.

Similar to green waste

Agriculture

8 Does not routinely compost wood wastes but have composted sawdust.

Process not altered Very small Excess cardboard obtained at the end of the process which is re-circulated

PAS 100 accredited Agriculture

9 5,000 tonnes of clean wood waste, e.g. pallets.

Processed in exactly the same as green waste.

Depends on seasonality and other factors.

Economics – obtain gate fee, and product can be sold £0-4.

Similar to green waste.

Agriculture or land restoration.

10 Do not compost wood wastes but do receive it for treatment by other processes.

Previous experience indicated that composting needs to be carefully managed, as the pile heats up very quickly and there is an increased fire risk.

Wood increases porosity.

Very high dust generation during shredding.

11 Composting now out-sourced.

A cardboard composting trial resulted in dried material which did not shred very well.




12 Mature bark and forestry residues.

Do not compost wood wastes.

13 Kerbside collected cardboard.

Wetting cardboard. Dependent on seasonality

10-20% to 75%.

Optimal approximately 10%.

Higher gate fee.

Avoid separation of card-board.

Product screened to 10 mm can be sold at £2-8/tonne.

Screened cardboard has a negative value.

Lower value than green waste.

Land restoration, landfill restoration.

14 Do not compost wood but operate a wood recycling plant that produces mulches.

15 Wood waste split into two grades – the lower grade is composted.

Shredded, mixed with green waste and co-composted with liquid wastes.

Depends on overall characteristics.

Diverted from landfill and liquid wastes are treated.

Contaminants do not generally pose a problem.



5 CASE STUDY

A site visit to Yorwaste’s Harewood Composting site was undertaken as part of the project. The site composts 30,000 tonnes of source segregated green waste per annum from Household Waste Recycling Centres. In addition wood waste is also composted using a different methodology.

5.1 Waste types sources and quantities At Yorwaste the wood waste (Figure 4) is categorised into two discrete categories. The higher grade, cleaner material is sent on to wood recyclers, while the lower grade material is composted. The wood waste is typical Civic Amenity site waste containing doors, panels, tables etc.

Figure 4 Wood waste prior to treatment at Harewood

5.2 Compost processing The wood waste is shredded to 50 mm using a hammer shredder. In some cases the material is to reduced in size prior to this in order to be fed into the shredder. The shredded green waste is mixed with civic amenity site waste to make a mix of 80% wood and 20% green waste, after which the mixture is co-composted with liquid wastes. The co-composting process adds necessary moisture to the composting mix.


Figure 5 Co-composting wood and green waste

5.3 Product and quality

A friable compost product is produced as pictured in Figure 6. However, due to the nature of the input material the quality of the end product is variable so the material is only used for landfill restoration


Figure 6 Composted production in windrow

5.4 Recommendations for the trials

On the basis of the operator survey and the case study the following recommendations are made for the trials:

• the wood/cardboard should be wetted;

• Liquid wastes may be added;

• The material should be finely shredded to help the composting process;

• An inclusion rate of 10% cardboard (v/v) produces good results but is not necessarily the maximum possible;

• There are no definite conclusions regarding an optimal inclusion rate for wood waste composting, so it is recommended to be cautious with the inclusion rate;

• Procedures should be introduced to reduce generation of dust during wood shredding; and

• Chemical and physical contamination should be assessed.


6 Composting trials

This section reports the results of trials carried out at the Envar composting site at St Ives in Cambridgeshire. There were 20 trials involving: • Cardboard; • Wood wastes; and • Market wastes. The overall aims of the trials were to: • Determine the maximum inclusion rate that could be safely incorporated into the compost; • Determine pre-treatment requirements; • Establish processing requirements; and • Identify the benefits of including the waste in the compost mix.

6.1 Cardboard Trials were carried out in duplicate to assess the effect of the addition of cardboard on the composting process and on the quality of the end product. The trials were based on kerbside collected garden and kitchen waste containing cardboard. The rationale for this was twofold: firstly there is an increasing number of councils that would like to include cardboard in their collections, and secondly if cardboard is to be collected for composting it is more likely to be included in a kerbside green and kitchen waste collection. The following trials were therefore carried out: • Control (kerbside collected garden, kitchen and cardboard waste); • Card 1 (kerbside collected garden, kitchen and cardboard waste); • Card 2 (kerbside collected garden, kitchen and cardboard waste); • Card extra 1 (kerbside collected garden, kitchen and cardboard waste with 5% added cardboard); and • Card extra 2 (kerbside collected garden, kitchen and cardboard waste with 5% added cardboard). 6.1.1 The Feedstocks The kerbside collected material was a typical household garden and food wastes containing cardboard. The additional cardboard added was corrugated cardboard used to for the packaging of fruit and vegetables. Figure 7 and 8 shows the shredded kerbside collection mix with card.


Figure 7 Source separated kerbside waste

Figure 8 Source separated kerbside waste with additional cardboard


Chemical analysis Prior to composting, the shredded feedstocks were analysed as shown in Table 6. The dry matter (DM) ranged from 266 g/kg to 397 g/kg (or 60-73% water content). The relatively high moisture was partially due to the feedstock being thoroughly soaked before composting commenced. The bulk density ranged from 224 g/l to 271 g/l, and was on average 88 g/l less dense where extra card was incorporated at 5%.

Table 6 Analysis of the cardboard trial feedstocks

Sample type In-vessel control

Card 1 Card 2 Card average

Card Extra 1

Card Extra 2

Card extra average

Dry matter (DM) (g/kg) 382 266 351 309 372 397 385Bulk density (g/l) 271 354 338 346 224 292 258total nitrogen (g/kg) DM 11.1 19.1 15.9 17.5 14.1 13.3 13.7Nitrogen % DM 1.1 1.9 1.6 1.8 1.4 1.3 1.4Organic carbon %m/m 30.3 34.2 14.4 24.3 21.4 25.5 23.5C:N ratio 27.6 18.0 9.0 13.5 15.3 19.6 16.8Lead (mg/kg) DM 62.0 21.4 64.2 42.8 58.8 54.2 56.5Nickel (mg/kg) DM 8.1 6.2 9.7 8.0 11.0 15.1 13.1Zinc (mg/kg) DM 108 66 112 89 119 131 125Cadmium (mg/kg) DM 0.5 0.3 0.5 0.4 0.5 0.3 0.4Chromium (mg/kg) DM 16.7 6.4 12.0 9.2 11.6 13.6 12.6Copper (mg/kg) DM 34.6 16.0 30.4 23.2 28.9 30.6 29.8Mercury (mg/kg) DM 0.1 0.0 0.1 0.1 0.1 0.5 0.3 Incorporation rate Waste analysis of the cardboard was carried out after the material had been shredded. The overall percentage of cardboard (as received) was 16.3 %. There were also large pieces of cardboard that had passed directly through the shredder, which accounted for 2.5%. Many composting facilities have developed experience through the use of particular feedstocks. Although these may vary with seasonality the site will know what to expect and how to deal with these variations. When dealing with new materials the C:N ratio and moisture content are normally considered. The feedstock analysis demonstrated that the carbon and nitrogen levels were suitable for composting and the moisture content was amended by the addition of water. In general the carbon to nitrogen ratio of 25-40:1 is considered optimal. Since the C:N ratio was unknown at the time of incorporation so could not be used to optimise the inclusion rate, therefore cardboard was added to excess. In practice this resulted in was 5% additional card to the 16% that was already present.

Table 7 Incorporation rate of the composting mixes

Trial Cardboard Incorporation rate

Control (kerbside collected garden, kitchen and cardboard waste) As received (16%) Cardboard trials Card 1 (kerbside collected garden, kitchen and cardboard waste) As received (16%) Card 2 (kerbside collected garden, kitchen and cardboard waste) As received (16%) Card extra 1 (kerbside collected garden, kitchen and cardboard waste with 5% added cardboard)

c. 5% extra, 21% overall (w/w)

Card extra 2 (kerbside collected garden, kitchen and cardboard waste with 5% added cardboard)

c. 5% extra, 21% overall (w/w)


6.1.2 Feedstock preparation Particle size reduction The particle size of the feedstock was reduced using a hammer and flails shredder. This resulted in the kitchen and green waste being reduced to <6 cm in diameter in compliance with the Animal By-Products Regulations (2003). The majority of the cardboard was shredded effectively. However, a small proportion passed directly through the shredder without the particle size being reduced (Figure 8). In addition, it would have been desirable if some of the card that was actually shredded could have been reduced in size even further before composting. Mixing and wetting The cardboard was soaked with water whilst mixing with the kerbside collected garden and kitchen waste. The feedstocks were first weighed using a tractor and trailer at the weigh-bridge. The materials were then mixed using the ‘volume of the bucket loader’ to estimate the proportion of each feedstock. Materials were added whilst shredding to aid the mixing of materials in the quantities shown in Table 8.

Table 8 The weights of feedstocks added Trial Weight at start

(tonnes) Percentage of

cardboard Control 112 as received Card 1 104 as received Card 2 105 as received Card extra 1 106 4.1 (w/w) Card extra 2 105 4.5 (w/w)

6.1.3 Composting process The feedstocks were composted within a batch tunnel for one week. During that time temperature was monitored continuously ensuring that all the material reached 60oC for two days as required to treat ‘meat excluded’ kerbside collected green and kitchen waste. A scan of the computer print out of the time-temperature profile of the first trial (CARD 1) is shown in Figure 9. The upper 5 lines are temperature probes in the compost. The graph shows the temperature rising over the first 24 hours until it reaches 60 degrees, at which the compost is maintained for 48 hours, then it is cooled to enable removal from the batch tunnel. Composting then continued in windrows. The windrows were turned weekly and the temperature monitored using hand held temperature probes. The data (Table 9) show that once the material has been in the composting in-vessel it is relatively dry but still contained sufficient moisture for composting to proceed. CARD 1 did become too dry 10 weeks into the process (see Appendix I), however no water addition took place at this point as the material was nearly ready to be screened.


Figure 9 Scan of the time-temperature profile of the first cardboard trial (CARD 1)


Table 9 Temperature and moisture monitoring in windrows after processing in-vessel

BATCH TEMPERATURE READINGS

Point 1 Point 2 Point 3 Core (oC)

(1 metre) Surface(oC) (0.5 metre)

Core (oC) (1 metre)

Surface(oC)(0.5 metre)

Core(oC) (1 metre)

Surface(oC) (0.5 metre)

Moisture1

CONTROL Min 52.9 56.3 51.6 56.8 53.7 57.1 2 Max 77.0 78.0 76.2 78.5 79.9 79.9 2 Average 65.7 69.4 64.6 68.8 67.0 69.7 CARD 1 Min 56.1 55.0 58.4 54.1 61.5 55.6 2 Max 78.3 69.0 77.7 71.3 692.0 69.8 3 Average 66.9 60.3 67.9 60.7 120.2 60.5 CARD 2 Min 55.3 44.8 56.3 45.8 55.9 46.8 2 Max 71.1 66.5 74.6 68.8 74.6 64.2 2 Average 64.9 57.7 65.2 60.2 66.2 56.3 CARD EXTRA 1 Min 58.3 55.2 60.1 56.6 64.6 53.2 2 Max 69.9 64.2 72.6 67.2 76.8 66.4 2 Average 64.1 59.5 67.6 61.8 69.4 61.6 CARD EXTRA 2 Min 55.8 44.2 56.7 48.7 58.3 49.7 2 Max 78.3 78 77.7 78.5 692 79.9 2 Average 62.7 54.2 64.7 56.3 62.7 55.7 1 Moisture content Key 1. Too wet 2. Near optimum 3. Too dry 6.1.4 Screening The final product was screened to 10 mm in a McCloskey’s 621 trommel. Mass Balance Each run was weighed before and after composting. Following screening both the product and the oversize were weighed to assess the break down of material during the composting process. The composting runs all showed a large decrease in mass during the composting run, reducing by approximately 60%. Of the remaining material between 28-34% was oversize material (greater than 10 mm) and the remaining 66% to 72% was product that passed through the trommel screen. The mass reduction in the extra card trial was approximately 10% less than that of the card trials, this would appear to be mainly due to a loss in moisture as Card 1 and 2 had on average 10% more water at the start than the extra card trials.


Table 10 Mass balance of waste, compost and oversize material

Weight at start

(tonnes)

Weight at end

(tonnes)

Percentage loss (%)

Weight of product less than 10 mm

(tonnes)

Weight of oversize(tonnes)

Percentage of sub 10 mm

product (%)

Control 112 46 59 30 15 66 Card 1 104 44 58 31 12 72 Card 2 105 45 58 29 16 64 Card extra 1 106 54 49 35 18 66 Card extra 2 106 56 52 36 20 64 6.1.5 Product quality A number of concerns have been raised regarding the effect of adding card on the quality of compost. These include the inclusion of inks, wax coating, cellotape, and staples. The quality of the end product was therefore assessed by the following criteria • Physical and chemical characteristics • Nutrients • Comparison to the Publicly Available Specification for Composted Materials and EN13432 for compostable packaging Physical and chemical characteristics The general physical and chemical characteristics were analysed as shown in Table 11. The dry matter averaged approximately 60%, and there was little difference across the composts. The organic matter indicated by Loss on Ignition (LOI) analysis was very high indicating a high content of humus, which is beneficial to soils. The bulk density of the compost derived from feedstocks containing additional cardboard was lower than the garden waste control indicating a more open structure. The pH (8-9) and carbon to nitrogen ratio (14-18) were within levels expected. The C:N ratio appeared to increase as more cardboard was incorporated in the feedstock. The higher cardboard content also reduced the conductivity of the compost.

Table 11 Physical and chemical characteristics of compost produced from kerbside collected garden, kitchen and cardboard waste

In-vessel

control

Card 1 Card 2 Card average

Card Extra 1

Card extra 2

Card extra

average Dry matter (g/kg) 630 704 479 592 578 597 588 Bulk density (g/L) 379 343 388 366 327 356 342 Total N (g/kg) DM 18.5 19.3 20.2 19.8 17.8 18.2 18.0 Nitrogen % DM 1.9 1.9 2.0 2.0 1.8 1.9 1.9 LOI (g/100) dry matter 52.7 47.3 52.6 50.0 55.9 48.7 52.3 Est organic carbon % m/m 30 27 30 29 32 28 30 C:N ratio 16 14 15 15 18 15 17 pH 9.0 9.1 8.8 9.0 9.2 8.4 8.8 Conductivity (μS/cm 20oC) 1505 1500 1330 1415 952 1400 1176 Nutrients CAT extraction (extracting nutrients using a media containing calcium chloride and DTPA) detects higher nutrient levels than water extraction and is believed to more accurately reflect what a plant or crop experiences in the compost in the medium to long term. Experience indicates it is particularly useful for phosphorus, magnesium, iron and zinc. Levels of these four nutrients (Table 12) are satisfactory for supporting plant growth in all composts. Water is the extractant normally used for analysis of peat-based growing media and is able to detect the immediately available supply of nutrients. It is relied on mainly for nitrate-N, ammonium-N, potassium and chloride. The ammonium-N values are satisfactory, and potassium levels are relatively high compared to organic fertilisers. Chloride levels are higher than required by plants, indicative of increased conductivity. The values for nitrate-N are very low compared to garden waste compost and manures indicating that there was little readily available nitrogen present.


Table 12 The nutrient value of compost produced in the card trials In-vessel

controlCard 1 Card 2 Card

averageCard

Extra 1Card

extra 2 Card

extra average

DTPA Extractable nutrients Phosphorus (mg/l) 54 67 42 55 46 53 50Potassium (mg/l) 2965 3110 2440 2775 1920 2180 2050Magnesium (mg/l) 170 186 172 179 156 184 170Sodium (mg/l) 289 279 206 243 209 247 228Sulphur (mg/l) 278 370 343 357 143 458 301Boron (mg/l) 42 2.8 2.4 2.6 2.6 2.9 2.8Copper (mg/l) <0.5 0.7 0.5 0.6 0.8 0.8 0.8Iron (mg/l) 46 39 44 41 40 37 38Manganese (mg/l) 37 38 31 35 27 33 30.0Zinc (mg/l) 10.8 12.5 9.7 11.1 8.6 10.2 9.4Molybdenum (mg/l) 0.2 0.1 0.1 0.1 < 0.1 < 0.1 <0.1 Water soluble nutrients Boron (mg/l) 1.7 1.5 1.4 1.4 1.3 1.4 1.4Molybdenum (mg/l) 0.3 0.4 0.3 0.3 0.3 0.2 0.2Ammonium-N (mg/l) 110 82 47 65 21 14 18Nitrate-N (mg/l) <5 6 < 5 6 < 5 < 5 <5Chloride (mg/l) 908 960 710 835 595 655 625Potassium (mg/l) 1800 1950 1640 1795 1260 1650 1455Magnesium (mg/l) 17 18 25 22 14 44 29Calcium (mg/l) 89 92 125 109 72 237 155Na (mg/l) 187 190 163 177 155 214 185Iron (mg/l) 6.5 5.4 4.5 4.9 4.3 2.4 3.3Phosphorus (mg/l) 24 27 15 21 19 13 16Copper (mg/l) < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5Manganese (mg/l) 0.5 0.5 0.4 0.5 0.4 0.5 0.4Zinc (mg/l) 0.5 0.5 0.5 0.5 0.5 0.3 0.4Sulphur (mg/l) 279 283 366 325 184 571 378 Total nutrients Phosphorus (mg/kg) DM 3995 3490 3870 3680 3080 2930 3005Calcium (mg/kg) DM 44850 37100 46500 41800 38100 41500 39800Potassium (mg/kg) DM 16900 15300 15900 15600 13700 13200 13450Sodium (mg/kg) DM 1450 1220 1240 1230 1320 1370 1345Manganese (mg/kg) DM 461 454 463 459 455 437 446Iron (mg/kg) DM 12600 17500 11700 14600 12300 12000 12150Nitrogen (g/100g) DM 1.9 1.9 2.0 2.0 1.8 1.8 1.80Sulphur (mg/kg) DM 5840 3810 5980 4895 3750 5380 4565Magnesium (mg/kg) DM 3100 3100 3480 3290 3060 3080 3070Boron (mg/kg) DM 42 37 40 39 46 48 47Molybdenum (mg/kg) DM 4.1 2.5 4.5 3.5 2.7 3.0 2.9

Comparison to the Publicly Available Specification for composted materials (PAS 100:2005) The quality of the end product was compared to PAS 100:2005. Table 13 depicts each card run against the PAS 100 limit in the right hand column. All the analysis were within the limits set for PAS 100, with the exception of Card Extra 2 that was not sufficiently stable, leading to poor growth in the bioassay trial, and the control that had physical contamination 0.2% above the specification. The instability (Card Extra 2 compost) was probably the cause of the plant growth not achieving the PAS 100 minimum of 80% growth compared to controls, but the compost would become more stable with time. The 0.2% above the glass found in the control run was due to a large fragment of glass in the 2-4 mm fraction.


Table 13 Comparison of the composting trials using a cardboard containing feedstock to PAS 100 In-vessel

control Card 1 Card 2 Card

averageCard

Extra 1Card

extra 2 Card

extra average

PAS 100 limit

Stability Compost Stability (mgCO2/gV/d) 10.8 9.4 13.1 11.3 10.3 21.9 16.1 16

Pathogens Escherichia coli (cfu/g) <10 < 10 < 10 <10 < 10 < 10 <10 1000Salmonella (/25g) N D N D N D N D N D N D N D Absent

Heavy metals Total Lead (mg/kg) DM 119 104 103 104 88 82 85 200Total Nickel (mg/kg) DM 13 15.5 13.4 14.5 13.5 12.7 13.1 50Total Zinc (mg/kg) DM 198 218 187 203 183 175 179 400Total Cadmium (mg/kg) DM 0.8 0.7 0.7 0.7 0.7 0.8 0.7 1.5Total Chromium (mg/kg) DM 21 21 23 22 19 26 23 100Total Copper (mg/kg) DM 65 60 80 70 60 51 55 200Total Mercury (mg/kg) DM 0.6 0.4 0.2 0.3 0.2 0.2 0.2 1.0

Plant growth test Percentage germination compared to control (5)

102 100 100 100 100 100 100 80

Percentage Fresh wt compared to controls (5)

92 88 82 85 92 75 83 80

Comments Comment1 Comment2 Comment3 Comment4 Comment5 No abnormalities

Physical contaminants Percentage of glass, metal and plastic over 2mm (%)

0.7 0.0 0.0 0.0 0.0 0.0 0.0 0.5

Percentage of plastic over 2mm (%)

0 0 0 0 0 0 0 0.25

Percentage of stones > 4mm (%) 0.5 4.2 5.9 5.1 4.5 2.1 3.3 8Total sharps 0 0 0 0 0 0 0 0

Weeds Weeds No of weeds per litres 0 0 0 0 0 0 0 0 Pass / fail Fail Pass Pass Pass Pass Fail Pass

Comment 1. Sample 1 – All mid green. Test plants had strong leaf purpling. Sample 2 - All mid green. Slight interveinal

chlorosis on some of the oldest leaves. Test plants had slightly more leaf purpling than the controls. 2. Card 1 – Only 2 test plants had emerged by 7 days. All plants were mid green with slight leaf purpling. 3. Card 2 – None of the control plants had emerged by 7 days. All the test plants had slightly more leaf purpling than

the controls 4. Card Extra 1 – No plants had emerged by 7 days. The test plants had slightly more purpling than the control. All

were mid green 5. Card Extra 2 – Only 2 test plants had emerged by 7 days. All plants were mid-green with very slight leaf purpling Comparison to the European Standard for Compostable Packaging and fate of heavy metals There are a number of standards for compostable packaging but the EU standard EN13432 is the most applicable to the UK. Packaging that meets the standard is considered biodegradable within the composting time frame and to have low toxicity. The standard requires that the heavy metal criteria below are met for the packaging to be certified as compostable. The heavy metal limits in EN13432 are proportionately based on the EU Eco-label for compost products. The heavy metals were measured at the start and the end of the process. Looking at the compost data only it appears that the cardboard is contributing to the heavy metal content at the start of the process. However, examination of the


card itself showed that concentrations in the card were lower than in the compost. The heavy metal levels in the card were below the limits set in the compostable packaging standard. At the end of the process the heavy metal concentration appears similar in all the composts. Closer examination reveals that cadmium, chromium and nickel are similar, but lead, zinc and mercury are reduced in the compost derived from extra card. During the composting process the heavy metal concentration increases, rising by (90%) lead, (40%) nickel, (70%) zinc and (70%) cadmium. The increase in copper and mercury levels was much less at 17% and 24% respectively. Since there was no source of additional heavy metals these results indicate that those present at the start have become more concentrated during the process, which is possibly due to the heavy metals being more readily associated with the smaller screened fraction. Table 14 Comparison of the heavy metals at the start and end of the process, and against EN13432 in the

cardboard feedstock In-

vessel Card 1 Card 2 Card

averageCard

Extra 1Card

extra 2Card

extra average

Card only EN13432LIMITS

Total heavy metals at the start

Lead (mg/kg) DM 62 21 64 43 59 54 57 19.2 50Nickel (mg/kg) DM 8.1 6.2 9.7 8.0 11.0 15.1 13.1 3.6 25Zinc (mg/kg) DM 108 66 112 89 119 131 125 83.3 150Cadmium (mg/kg) DM 0.5 0.3 0.5 0.4 0.5 0.3 0.4 <0.25 0.5Chromium (mg/kg) DM 17 6 12 9 12 14 13 6.6 50Copper (mg/kg) DM 35 16 30 23 29 31 30 22.5 50Mercury (mg/kg) DM 0.1 0.0 0.1 0.1 0.1 0.5 0.3 0.1 0.5Molybdenom (mg/kg) DM n/a n/a n/a n/a n/a n/a n/a 0.8 1Selenium (mg/kg) DM n/a n/a n/a n/a n/a n/a n/a 0.1 0.75Arsenic (mg/kg) DM n/a n/a n/a n/a n/a n/a n/a 1.7 5Fluorine (mg/kg) DM n/a n/a n/a n/a n/a n/a n/a 21.1 100 Total heavy metals in the product

Lead (mg/kg) DM 119 104 103 104 88 82 85 Nickel (mg/kg) DM 13 16 13 15 15 13 13 Zinc (mg/kg) DM 198 218 187 203 183 175 179 Cadmium (mg/kg) DM 0.8 0.7 0.7 0.7 0.70 0.8 0.7 Chromium (mg/kg) DM 21 21 23 22 19 26 23 Copper (mg/kg) DM 65 60 80 70 60 51 55 Mercury (mg/kg) DM 0.6 0.4 0.2 0.3 0.2 0.2 0.2


6.1.6 Conclusion of the cardboard composting trials Collection The cardboard composting was collected from two sources. The first source was a kerbside collection of garden, kitchen and cardboard. The level of cardboard received in these collections is difficult to control. Given these difficulties a robust composting technology is required as the feedstock may not always be optimal for composting, especially during winter months. Processing The composting of cardboard is feasible if precautions are taken. The addition of dry cardboard can dry out the composting process. Therefore, the cardboard needs to be sufficiently wetted when mixed with other feedstocks. Wetting at the start of the process as opposed to during the process can minimise run-off. Shredding cardboard is quite difficult and compost producers should consider the type of shredder they purchase if they intend to process card. The hammer and flails shredder used in this trial was adequate but did not shred the entire card feedstock. A hammer shredder is likely to perform better, while a chipper shredder will not be suitable for card. The data show that the compost can reach adequate temperatures to satisfy Animal By-Product Regulations, and demonstrated effective composting. Maximum inclusion rate A quality compost product was produced from trials, which met the PAS 100. It is therefore feasible to compost cardboard as received (16% card) in a kerbside collection. Also the trials showed that the addition of 5% extra card (w/w) to mimic an abnormally high cardboard inclusion rate did not have any deleterious effect on the composting process. Benefits and disadvantages The compost produced from feedstock including card had desirable characteristics. The potassium levels were good and it had a fibrous and light structure. When the compost was screened to 10 mm approximately 30% of the product was lost as oversize material. A significant proportion of this oversize material was organic matter. A more powerful shredder and more rigorous turning regime may enable a quality compost to be produced at 25 mm. Seasonal variability During the winter the proportion of cardboard increases (as a consequence of there being less garden waste). This material can still be composted but it is more difficult. 6.1.7 Further research Further research can be carried out on composting cardboard: • Comparison of the cardboard trials against card excluded compost; • Comparison of the quantity of compost that may be achieved from using 25 mm screen instead of 10 mm; • Analysis of the cardboard content of the oversize material; • The effect of seasonal variation on feedstock composition; and • The use of a more powerful shredder to reduce the particle size of the cardboard further.


6.2 Chipboard Chipboard was identified as a material that is problematic to divert from landfill, but which could potentially be composted and applied beneficially to land. The use of wood in composting is already well established, so composting chipboard should be feasible providing the material can be handled by existing machinery at a composting site and the product is of suitable quality. The following trials were carried out: Windrow trials Control (garden waste only); Chip 1 (garden waste and chipboard); and Chip 2 (garden waste and chipboard). In-vessel composting Control (kerbside collected garden, kitchen and cardboard waste); Tunnel Chip 1 (kerbside collected garden, kitchen and cardboard waste); and Tunnel Chip 2 (kerbside collected garden, kitchen and cardboard waste). 6.2.1 Feedstock The feedstocks Large flat boards (approximately 3m by 2m) as shown in Figure 10 and Figure 11 were used. The boards were quite thick and difficult to handle requiring a fork lift with a 7.5 tonne loading capacity. The board was stored indoors (Figue 10) until the trial could commence.

Figure 10 Chipboard stacked on pallets as delivered


Figure 11 Close view of the chipboard

Chemical analysis and incorporation rates Analysis of the board was carried out. As expected, it had a high organic matter and carbon content. The heavy metals present were lower than normally found in the compost products, so would be expected to have a dilution effect. However, there were fairly high levels of formaldehyde at 1100 mg/kg. The analysis also shows that there was 32.7 mg/kg of nitrogen, which is approximately double that of garden waste. Data obtained from the supplier and the high nitrogen levels indicate that that the wood is glued together with Urea Formaldehyde, which is also used as a slow release fertiliser and regulated under The Fertiliser (Amendment) Regulation 1995.

Table 15 Chipboard analysis Chemical ConcentrationCadmium (mg/kg) 0.18 Chromium (mg/kg) 3.76 Copper (mg/kg) 8.07 Mercury (mg/kg) <0.01 Nickel (mg/kg) < 2.0 Lead (mg/kg) 17.2 Zinc (mg/kg) 21.5 Loss on ignition g/100g 97.1 Nitrogen (g/kg) 32.7 Organic carbon (% m/m)

41.9

Formaldehyde (mg/kg) 1100

Although the carbon to nitrogen ratio of chipboard (13:1) indicates that it could be mixed with garden waste at a high rate,eg 2 parts garden waste to 1 part chipboard, the effect this might have on the end product in terms of appearance and quality is unknown. Therefore a lower incorporation rate of 10% (Table 16) was used in windrows. The chipboard was incorporated with the garden and kitchen waste at a reduced rate of 5% in-vessel to insure against any negative possible impact on achieving the minimum temperature profile required by the Animal By-Product Regulations 2003.


Table 16 Incorporation rate of chipboard in the trial runs Trial Chipboard

percentage (%)

Garden waste (windrow) Control 0% Chip 1 (garden waste and chipboard) 10% Chip 2 (garden waste and chipboard) 10% Garden waste and kitchen waste (In-vessel) Control (kerbside collected garden, kitchen and cardboard waste) 0% Tunnel Chip 1 (chipboard and kerbside collected garden, kitchen and cardboard waste) 5% Tunnel Chip 2 (chipboard and kerbside collected garden, kitchen and cardboard waste) 5%

Table 17 shows the chemical analysis of the chipboard and garden waste. The dry matter content is very high indicating that the mixture required further wetting. The data show that the chipboard mixture had a higher nitrogen content than the garden waste alone. The organic carbon analysis was low due to the fact that the Tinsley method of analysis was used. Higher organic carbon would be expected in the chipboard mix compared to the controls but the data show the opposite. The reason for this result is unclear but probably lies with the method of determination. There are many methods that can be used to determine the organic carbon content. The Tinsley method is commonly used for soil and sediments and is more accurate and precise than many other similar methods e.g. Walkley-Black. The Tinsley method is based on heated dichromate extraction and titration. Another method, often used for compost is LOI (Loss on Ignition method) which involves heating the sample in a crucible to 350-440oC overnight. The sample is then cooled in a dessicator and weighed. The difference between the initial and end mass is then used to calculate the percentage of organic matter, and a conversion factor applied to calculate the organic carbon. Traditionally, for soils, a conversion factor of 1.724 has been used based on the assumption that soil contains 58% organic carbon. However, soil carbon does vary from soil to soil, and within the soil profile. A conversion factor as high as 2.5 may be used for some sub-soils. However, this method often leads to a over-estimation because clay minerals will lose structural water or hydroxyl groups. Despite this lack of accuracy the data would suggest that it may have been preferable to use the LOI method as the Tinsley method underestimates the organic carbon content at high soil carbon concentrations. This is clearly evident (Table 18) where the both methods were compared for second garden and kitchen waste trial. The organic carbon content calculated using the Loss on Ignition method is virtually double the Tinsley method.

Table 17 Chemical analysis of the garden waste and chipboard feedstock mixture Sample type Windrow

controlGarden

waste Chip 1

Garden waste Chip 2

Garden waste Chip

average Dry matter(g/kg) 547 674 661 668 Bulk density 269 320 312 318 Total nitrogen (g/kg) DM 11.0 17.4 23.1 20.3 Nitrogen % 1.1 1.7 2.3 2.0 Organic carbon %m/m (Tinsley) 18.8 12.0 16.0 14.0 Formaldehyde (mg/kg) <5.0 53.0 55.4 54.2

Analysis was carried out on the chipboard and catering/garden wastes mixture. The dry matter contents are low compared to the optimum for composting (50-60%) due to fact that all feedstocks entering the composting tunnels were wetted. Only 5% chipboard was added to the runs so the level of nitrogen and formaldehyde was reduced compared to the windrow trials. Again the results suggest that the organic carbon is lower than in the controls using the Tinsley method (as discussed previously).


Table 18 Chemical analysis of the garden, kitchen and chipboard feedstock mixture

Sample type TunnelControl

Tunnel Chip 1

Tunnel Chip 2

Tunnel Chip

average Dry matter(g/kg) 382 391 311 391 Bulk density 271 324 420 324

total nitrogen (g/kg) DM 11.1 13.6 10.7 13.6 Nitrogen % 1.11 1.36 1.07 1.36 Organic carbon %m/m (Tynsley) 30.3 20.2 19.6 20.2 Estimated from organic carbon % m/m (LOI)

38.5

Formaldehyde 2.5 32.5 36.1 34.3 6.2.2 Feedstock preparation Particle size reduction The material was prepared for composting by reducing its particle size. First the large boards were broken into smaller pieces using a bucket loader, resulting in jagged, irregular shaped boards as shown in Figure 12. These pieces were then shredded as shown in Figure 13 to produce small fines. There was still a small proportion of the board in small compressed blocks. The shredding process was quite slow compared to shredding garden waste and work had to stop twice to un-block the shredder.

Figure 12 Large pieces of broken chipboard


Figure 13 Shredded chipboard

Mixing and wetting The chipboard material was added to the other waste as the latter was shredded thus going though the shredder a second time. The initial analysis (Table 17) revealed that the material was very dry so the windrows were wetted up using a bowser. The chipboard was difficult to handle for the following reasons: • The boards were very large; • Once shredded the fines created dust which blocked the radiators in plant equipment; and • Personal protective equipment was also required due to the dust and formaldehyde present.

Figure 14 Wetting the chipboard and garden waste


Figure 15 Mixing the chipboard and garden waste using the shredder and bucket loader

6.2.3 Composting The garden waste chipboard mixture was composted in windrows approximately 2.5 metres high, 3 metres wide and 4 metres long. The windrows were weighed before formation. Once formed they were turned weekly. The temperature was measured, and observations made of the moisture content. The ‘meat excluded’ kerbside collected garden and kitchen waste and chipboard trials were composted for one week in-vessels where the moisture and oxygen levels were carefully controlled by a temperature feedback system. The vessels were maintained as 60 oC for 2 days as required by the Animal By-Products Regulations (Figure 16). After one week in-vessel it was then composted in windrows, maintained at 55-60 oC. The moisture content as observed by the ‘squeeze’ test was at the drier end of the scale. After 10 weeks composting the compost was dry and friable to touch. Chemical analysis revealed that the formaldehyde levels had not reduced as much as expected so the windrows were re-wetted to assess whether formaldehyde would break down further.

Figure 16 Time temperature profile of chipboard tunnel 2


Table 19 Temperature and moisture contents during the windrow phase of composting chipboard with

garden or kerbside collected garden, kitchen and cardboard waste BATCH TEMPERATURE READINGS

Point 1 Point 2 Point 3 Moisture1 Core

(1 metre) Surface

(0.5 metre) Core

(1 metre) Surface

(0.5 metre)Core

(1 metre) Surface

(0.5 metre)

CHIP 1 (garden and chipboard waste) Min 54.3 46.6 57.0 56.7 57.0 52.6 2 Max 69.9 73.3 68.2 73.2 68.8 73.6 3 Average 61.9 64.7 61.9 65.5 62.1 61.1 CHIP 2 (garden and chipboard waste) Min 41.8 41.9 38.6 37.7 39.2 39.5 2 Max 79.9 69.9 76.4 69.9 72.4 67.2 3 Average 67.6 59.9 67.9 58.9 66.8 60.7 Tunnel Chip 1 (chipboard and kerbside collected garden, kitchen and cardboard waste) Min 50.6 41.1 50.2 41.2 52.1 43.5 2 Max 75.7 73.1 75.9 73.2 76.1 72.5 3 Average 66.3 61.1 65.9 59.9 65.2 60.0 Tunnel Chip 2 (chipboard and kerbside collected garden, kitchen and cardboard waste) Min 48.8 46.2 60.2 53.5 57.5 50.1 2 Max 74.5 66.7 74.8 73.4 74.5 68.4 3 Average 66.8 59.3 68.8 63.4 67.6 60.0 Moisture content key 1. Too wet 2. Near optimum 3. Too dry 6.2.4 Screening The compost was screened to 10 mm using a McCloskey’s 621 trommel, as shown in Figure 17. Close examination of the product shows a large number chipboard fines in the compost.


Figure 17 The compost product derived from 10% inclusion of chipboard with garden waste

Mass balance The mass balance was calculated (Table 20). Comparison of the garden waste control and chipboard trials shows that there was little mass loss during the process, in part due to a low moisture content at the start and low degradation. There was approximately 10% less product in the green waste control compared to the green waste and chipboard trials. The kitchen waste and garden waste trials also showed a similar pattern with approximately 5% more product than compared to the control. This is consistent with the quantity of chipboard that was added to the waste which, together with reduced percentage loss compared to the control, would suggest that the chipboard fines passed through the screen into the product and were not degraded to any major extent.

Table 20 Mass balance of the chipboard trials Weight at

start Weight at

endPercentage

lossWeight of

product less than 10 ml

Weight of oversize


product (%)

Green waste control 78 66 15 46 19 71Control 112 46 59 30 15 67Green waste chip 1 128 107 16 83 24 78Green waste chip 2 129 121 6 99 22 82Tunnel chip 1 105 49 53 34 15 69Tunnel chip 2 95 42 56 30 12 71 6.2.5 Product quality The quality of the end product was compared to both the controls and PAS 100, and contaminants not specifically referred to in PAS 100 were compared against levels in the controls only. General characteristics As expected the organic matter content of the chipboard trials was marginally higher than the controls. There were also higher levels of nitrogen in the compost derived from chipboard waste in both the garden waste and garden and kitchen waste trials. Visually, the compost (Figure 17 and Figure 18) looked lighter in colour than the controls and chipboard fines could clearly be seen.


Figure 18 Close up of compost product derived from 5% inclusion of chipboard with kerbside collected garden and kitchen waste

Table 21 Physical and chemical analysis of the chipboard compost Windrow

control Chip 1 chip 2 Garden

waste and chip average

Tunnelcontrol

Tunnel chip 1

Tunnel chip 2

Kerbside collected and chip average

Dry matter (g/kg) 660 742 751 747 630 573 591 582Bulk density (g/l) 450 433 403 418 379 357 442 400Total N (g/kg) 13.4 16.3 16.1 16.2 18.5 23.8 16.9 20.4Nitrogen % 1.3 1.6 1.6 1.6 1.9 2.4 1.7 2.LOI 33 39 38 38 53 57 54 55Est organic carbon % m/m 19 22 22 22 30 33 31 32PH 8.4 9.1 8.8 9.0 9.0 9.1 8.3 8.7Carbon to nitrogen ratio 14 14 14 14 16 14 18 16Conductivity (μS/cm 20oC) 1540 1220 1310 1265 1505 1300 1380 1340 Nutrients Levels of CAT (0.01 M CaCl2 and 0.002 DTPA [diethyletriaminepetnaaceticacid) extractable phosphorus, magnesium, iron and zinc were similar in all composts and all were entirely satisfactory to support plant growth as confirmed by the growth tests. Water-extractable potassium levels were very good compared to organic fertilisers e.g manures. The water extractable levels of phosphorus are under-estimated using this method due to the high pH. Chloride levels were high and could have some damaging effect on the roots of sensitive plants if the compost is used at a high rate of application. It has been calculated (Potash Development Association, www.pda.org.uk/notes/tn12.asp) that safe levels of chloride range from around 180mg/l for sensitive crops on light soils to 1800 mg/l for tolerant crops on heavy textured soils. Nitrate-N levels are higher than in the compost controls. The ammonium-N levels observed are unusually high, and if the compost was used in a growing medium at the recommended rate (20-33% depending on conductivity of the compost and peat) this could cause plant damage and could be the cause of the observed foliage symptoms in the growing test.


Table 22 Nutrient analysis of the chipboard compost

Windrow (garden waste)

Garden waste

and chip 1

Garden waste

and chip 2

Garden wast and

chip average

TunnelControl

Tunnel chip 1

Tunnel chip 2

Tunnel control

average

DTPA extractable nutrients Phosphorus (mg/l) 40 51 44 48 52 53 20 37Potassium (mg/l) 2370 2470 2230 2350 2965 2270 2340 2305Magnesium (mg/l) 179 150 145 148 170 130 164 147Sodium (mg/l) 138 146 130 138 289 233 345 289Sulphur (mg/l) 648 238 313 276 278 81 604 343Boron (mg/l) 1.7 2.0 1.7 1.9 3.3 2.5 3.2 2.8Copper (mg/l) 0.8 0.9 0.7 0.8 1.6 0.3 1.5 0.9Iron (mg/l) 43 42 36 39 46 34 50 42Manganese (mg/l) 9.0 20.9 17.1 19.0 36.5 30.8 25.7 28.3Zinc (mg/l) 8.3 9.4 7.4 8.4 10.8 8.9 11.7 10.3Molybdenum (mg/l) < 0.1 < 0.1 < 0.1 <0.1 0.2 0.2 0.1 0.2 Water soluble nutrients Boron (mg/l) 0.7 0.9 0.8 0.8 1.7 1.4 1.7 1.6Molybdenum (mg/l) 0.2 0.2 0.2 0.2 0.3 0.3 0.2 0.3Ammonium-N (mg/l) 19 161 194 178 110 216 64 140Nitrate-N (mg/l) 40 51 121 86 <5 8 95 52Chloride (mg/l) 793 720 670 695 908 795 821 808Potassium (mg/l) 1745 1320 1350 1335 1800 1370 1670 1520Magnesium (mg/l) 50 11 15 13 16.5 11 27 19Calcium (mg/l) 299 57 84 71 89 64 144 104Na (mg/l) 106 87 89 88 187 149 263 206Iron (mg/l) 1.7 7.1 4.7 5.9 6.5 9.2 5.0 7.1Phosphorus (mg/l) 7 18 11 15 24 32 8 20Copper (mg/l) < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 <0.5Manganese (mg/l) 0.5 0.2 0.2 0.2 0.5 0.7 0.4 0.5Zinc (mg/l) 0.2 0.3 0.3 0.3 0.5 0.8 0.4 0.6Sulphur (mg/l) 609 187 272 330 279 89 367 228 Total nutrients Phosphorus (mg/kg) DM 2505 2620 2570 2595 3995 2790 3150 2970Calcium (mg/kg) DM 46300 39400 39600 39500 44850 30000 68200 49100Potassium (mg/kg) DM 10400 10500 9240 9870 16900 12500 11900 12200Sodium (mg/kg) DM 639 605 572 588.5 1450 1230 1580 1405Manganese (mg/kg) DM 328 293 309 301 305 373 380 377Iron (mg/kg) DM 23300 20000 20600 20300 12600 11800 13000 12400Nitrogen (g/100g) DM 1.3 1.6 1.6 1.6 1.9 2.4 1.7 2.0Sulphur (mg/kg) DM 4980 3740 3670 3705 5840 2750 5420 4085Magnesium (mg/kg) DM 3810 3720 3600 3660 3100 2980 2910 2945Boron (mg/kg) DM 29 28 29 28 43 34 41 38Molybdenum (mg/kg) DM 13.6 2.8 3.1 3.0 4.1 3.6 5.3 4.5 Comparison to the Publicly Available Specification for Composted Material The composts were analysed in accordance with the methods prescribed in PAS 100 and assessed against the quality criteria (Table 23). The compost produced using chipboard complied with PAS 100 in all the categories but there were unfavourable comments in the bioassay trials, and that one trial had a high percentage of stones. Although the plants performed well in terms of germination, growth and weight, compared to controls there were some abnormalities in their appearance (plant purpling and inter-veinal chlorosis of the oldest leafs) reported. Chlorosis can occur for numerous reasons e.g lack of iron, zinc, manganese, compaction. The plants may be stressed by the level of formaldehyde present but the data does not necessarily support this as the tunnel controls (which do not contain significant levels of formaldehyde) also suffered from chlorosis of the leaves. The only composts that did not suffer any abnormalities were those produced from the garden waste control trial and the second 5% chipboard, garden and kitchen waste trial (tunnel chip 2). The garden waste trial composts had low levels of ammonium-N and formaldehyde in the final product, and the


second chipboard and catering/garden waste trial was the only test compost with low ammonium-N levels. The formaldehyde concentration in this compost was fairly high (25 mg/kg) at the time of sampling. In the garden waste and MDF composts the ammonium-N concentrations are high but the formaldehyde concentration (39 mg/kg) was also higher than the catering/garden waste trial so symptoms may have been caused by either. Overall, the compost produced was stable (as measured by CO2 evolution). Immature composts may contain high concentrations of organic acids, or other water-soluble compounds that may limit seed germination and root development. While immature compost tend to have higher levels of mineralised nitrogen, this can lead to nitrogen immobilisation, where mineralised nitrogen is converted to organic nitrogen, as the composts continues to degrade (combined with the possible volatilisation of ammonium-N) the overall availability of nitrogen to plants will decrease. The compost is also low in pathogens, heavy metals, physical contaminants and did not contain any weed seeds. One of the chipboard garden and kitchen waste trials (tunnel chip 2) had an unusually high test result for the percentage of stones (16.9%).

Table 23 Comparison of a garden and kerbside chipboard compost with PAS 100

Windrow Garden waste and

chip 1

Garden waste and

chip 2

Garden waste and

chip average

TunnelControl

Tunnel chip 1

Tunnel chip 2

Tunnel chip

average

PAS 100 limit

Stability Compost Stability (mgCO2/gV/d)

5.0 6.4 4.4 5.4 10.8 8.9 6.7 7.4 16.0

Pathogens Escherichia coli (cfu/g) <10 < 10 < 10 < 10 < 10 < 10 <10 <10 1000Salmonella (/25g) N D1 N D1 N D1 N D1 N D1 N D1 N D1 N D1 Absent

Heavy metal Total Lead (mg/kg) DM 81 72 93 83 119 72 77 75 200Total Nickel (mg/kg) DM 16 15 15 15 13 11 16 14 50Total Zinc (mg/kg) DM 203 171 180 176 198 154 205 180 400Total Cadmium (mg/kg) DM 0.5 0.5 0.5 0.5 0.8 0.7 0.6 0.6 1.5Total Chromium (mg/kg) DM 30 24 28 26 21 16 21 18 100Total Copper (mg/kg) DM 76 61 71 66 65 48 110 79 200Total Mercury (mg/kg) DM 0.2 0.1 0.2 0.1 0.6 0.1 0.2 0.1 1.0

Plant growth test Percentage germination compared to control

102 100 93 97 102 103 104 104 80

Percentage Fresh wt compared to controls

89 84 97 90 92 94 109 102 80

Comments/abnormalities Comment1 Comment2 Comment3 Comment4 Comment5 Comment6 No abnormalities

Physical contaminants Percentage of glass, metal and plastic over 2mm

0.2 0.2 0.0 0.1 0.7 0.0 0.0

0.0 0.5

Percentage of plastic over 2mm

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.25

Percentage of stones > 4mm 3.4 3.1 1.0 2.1 0.5 1.8 17.3 9.6 8Total sharps 0 0 0 0 0 0 0

0 0

Weeds Weeds No of weeds per litres 0 0 0 0 0 0 0 0 0 Pass/fail Pass Pass Pass Pass Fail Pass Fail Pass

Notes ND = Not detected


Comment/abnormality. 1. Windrow control (sample 1) - All mid green. Controls had very slight leaf purpling, test plants. Windrow control

(sample 2) - test plants had strong leaf purpling. All were mid green 2. Chip 1 - The test plants had slightly more purpling than the controls and slight inter-veinal chlorosis on the oldest

leaves 3. Chip 2 - The test plants had slightly more purpling than the controls and slight inter-veinal chlorosis on the oldest

leaves 4. Tunnel control (sample 1) - All mid green, test plants had strong leaf purpling, Tunnel control (sample 2) - All mid

green, slight interveinal chlorosis on some of the oldest leaves. Test plants had slightly more leaf purpling than the controls

5. Tunnel chip 1 - Test plants slight dark green with strong leaf purpling. Slight interveinal chlorosis of most of the oldest leaves

6. Tunnel chip 2 All mid green. Test plants slightly taller than the controls Contaminants outside the scope of PAS 100 The compost resulting from the trials was compared to the controls for a variety of contaminants that may be expected in wood e.g. • Fluoride (common preservative) • Arsenic (used in chromated copper arsenic) • PAHs (preservatives) • Polychlorinated bi-phenols (PCBs [used in paints]) • Phenols (phenol formaldehyde) In addition to those mentioned above there are numerous other organic contaminants that have been associated with wood used as either preservatives e.g. hydrocarbon (napthalene, fluorene), quaternary ammonium compounds, organoiodines, carboxylic acid derivatives, cyclodienes, isocyanates, dicarboximides, organophosphates, pyrethroids, triazoles and others. It was not possible to test for all these, and in any case the contaminants expected in the chipboard are likely to be associated with the bonding agents, which are usually volatile. Therefore, a suit of analysis was carried out on volatile organic compounds and semi-volatile organic compounds, which may indicate the presence of other contaminants if present at elevated levels. The levels of fluoride and arsenic were low in the compost containing chipboard compared to the controls. Although garden waste composts had higher levels of arsenic than garden and kitchen waste derived composts. The levels of Polyaromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs) and phenols were all low compared to the controls, and the majority were below levels of detection. Only formaldehyde (discussed in the next section) was found at a significantly higher level than in the controls.

Table 24 Comparison of other contaminants in compost with and without chipboard

WindrowControl

Garden waste

and chip

Tunnel control

Tunnel chip

Total Fluoride (mg/kg) DM 85.0 85.0 59.0 43.0 Total Arsenic (mg/kg) DM 11.0 10.3 6.8 5.8 PAH Naphthalene (mg/kg) Air Dried 2.5 3.0 4.1 6.0 Acenaphthylene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Acenaphtene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Fluorene (mg/kg) Air Dried 0.8 0.5 0.6 0.9 Phenanthrene (mg/kg) Air Dried <0.5 0.6 0.7 0.6 Anthracene (mg/kg) Air Dried < 0.50 < 0.5 <0.5 < 0.5 Fluoranthene (mg/kg) Air Dried 1.1 1.4 1.0 0.7 Pyrene (mg/kg) Air Dried 1.0 1.2 0.7 0.5 Benzo(a)anthracene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Chrysene (mg/kg) Air Dried 0.6 0.7 <0.5 < 0.5 Benzo(b)fluoranthene (mg/kg) Air Dried 0.8 1.1 0.9 0.9 Benzo(k)fluoranthene (mg/kg) Air Dried < 0.5 0.5 <0.5 < 0.5 Benzo(a)pyrene (mg/kg) Air Dried <0.5 0.8 <0.5 < 0.5


WindrowControl

Garden waste

and chip

Tunnel control

Tunnel chip

Dibenzo(ah)anthracene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Benzo(g,h,I)perylene (mg/kg) Air Dried 0.9 0.9 0.8 0.8 Indeno(123-cd)pyrene (mg/kg) Air Dried <0.5 0.6 <0.5 < 0.5 PAH Screen (mg/kg) 10 12 10.5 12 Formaldehyde (mg/kg) 1.3 39.2 0.9 25.3

VOC ANALYSIS (mg/kg) Below detection level 0.1 (see appendix)

SVOC ANALYSIS (mg/kg) Below detection level 1.0 (see appendix)

PCB CONGENERS (mg/kg) Below detection level 0.01 (see appendix)

PHENOLS (mg/kg) Catechol < 0.1 < 0.1 <0.1 < 0.1 Phenol < 0.1 0.1 0.1 0.1 Cresols < 0.1 < 0.1 <0.1 < 0.1 Xylenols < 0.1 < 0.1 <0.1 < 0.1 Trimethylphenol < 0.1 < 0.1 <0.1 < 0.1 Total phenols < 0.5 < 0.5 < 0.5 < 0.5

Formaldehyde The initial level of formaldehyde in the chipboard was 1100 mg/kg. The effect of mixing with the garden waste with chipboard significantly reduced the formaldehyde levels as shown in Table 25. A dilution effect of 90% in windrows and 95% in the tunnel would be expected based on the quantity of amendment material. However, the formaldehyde reduced by approximately 95% and 97% respectively. The reduction in formaldehyde during composting was much less than expected. The concentration of formaldehyde was reduced by 68% in garden waste and 39% in kerbside collected waste. The data in Figure 19 demonstrates the observed reduction over time. In all the trials the formaldehyde decreased, but the rate of decrease was markedly more in the garden waste, which had a higher initial concentration. At 30 weeks the levels converge.

Table 25 Formaldehyde reduction during the composting process of feedstock containing chipboard Formaldehyde in

the chipboard(mg/kg)

Initial formaldehyde concentration when

mixed (mg/kg)

Final formaldehyde concentration (mg/kg) after

30 weeks

Percentage reduction during composting (%)

Windrow (garden waste and chipboard 10%

1100 53.0 16.9 68

Tunnel (kerbside collected) and chipboard 5%

1100 34.3 20.1 39


Figure 19: The reduction in formaldehyde concentrations during composting chipboard

6.2.6 Conclusions of the chipboard composting trials Collection A clean source of chipboard is required for composting, so intensive segregation is required. This may be achieved at civic amenity sites, but is likely to require a further segregation step after being segregated by the public Processing Composting boards may also require specialist plant equipment to lift, break up and shred the material, so careful consideration is required when sourcing the waste. The chipboard fines also caused difficulties to the operation of equipment blocking the shredder twice and dust had to be routinely removed from the radiators of plant equipment. During the trials dust was generated and once the compost piles are formed the heat generation leads to the release of formaldehyde. The maximum exposure limit (MEL) for formaldehyde is two parts per million (2ppm), time weighted average over eight hours. The short-term limit (averaged over ten minutes) is 2ppm. Therefore occupational exposure must be controlled and appropriate protective clothing worn. The temperatures observed demonstrated that the trials were composting adequately. Maximum inclusion rate The screening and process data show that the chipboard may be composted at the incorporation rates used in the trials. However, chipboard fines were prominent in the compost product. This lack of degradation may be explained by a lack of degradation of the lignin within the composting timeframe. Wood is comprised of three main components cellulose, hemicellulose and lignin. Cellulose (long glucose chains) and hemicellulose (long branched glucose chains) can be degraded by a plethora of micro-organisms. Lignin, however, is far more complicated and therefore more recalcitrant. During composting actinomycetes and fungi are capable of breaking down lignin (actinomycetes would typically responsible for the less than 20 percent (Basaglia et al 1992)92 of the lignin degraded). There is much debate regarding the potential degradation of lignin ranging from none (Lynch and Wood, 1985)93 to 70% in olive wastes (Tomati et al, 1995)94, which implies that the matrix and surface area of the substrate are important. Although further degradation may be expected, as more surface area becomes available over time, it would be difficult to increase the incorporation rate above 10% without having a negative impact on the visual quality of the compost during a 12 week period. While the plants germinated and grew adequately they also showed plant chlorosis. These symptoms can be caused by a number of factors. The only contaminant found to be at higher levels than in the controls was formaldehyde. However, the ammonia levels were also high.

0

10

20

30

40

50

60

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

Weeks

Red

uctio

n in

form

alde

hyde

(mg/

kg)

Green waste (windrows only)

Kerbside green and kitchen waste (invessel one week then windrowed)


The data from trials on formaldehyde shows that a 5% incorporation rate has no negative impact on plants at 12 weeks, this may or may not be true at the 10% incorporation rate, but it is not possible to implicate formaldehyde as the sole cause of the observed effects. However, if the compost is left to mature for the 30 weeks, the formaldehyde concentration falls below the level observed at the 5% incorporation rate at 12 weeks. In conclusion, the data would suggest it is safe to incorporate 5% chipboard in to a 12 week composting process, or possibly 10% in to a 30-week process. The 30-week process time may be reduced if formaldehyde can be eliminated as a possible cause of the observed foliage symptoms, and even though foliage symptoms were reported these were not recorded as abnormalities by the laboratory so were not considered sufficiently severe to fail the PAS 100 growth test. Benefits and disadvantages The benefits of adding chipboard are: a higher nitrogen concentration in the garden waste and kerbside collected garden kitchen waste compost and potential gate fee. However, the material was difficult to process, and in particular, to maintain moisture levels. The windrows tended to become dry during composting and did not wet very well, once they had been formed. Ensuring there is sufficient moisture at the start was therefore essential. Urea formaldehyde is used a slow release fertiliser (covered by The Fertiliser (amendment) Regulations 1995). The data show that adding chipboard to garden waste increases the nitrogen concentration and therefore the provides additional beneficial nutrients in the form of nitrogen as urea formaldehyde is degraded over time. Wood based panels like chipboard may contain other forms of formaldehyde e.g phenol formaldehyde and melamine formaldehyde. It is not clear from these test results that composting is able to completely degrade these forms. Although, the literature search would indicate that composting can degrade phenol formaldehyde, there is less certainty regarding melamine formaldehyde. Therefore the exact type of formaldehyde present in the feedstock should be identified before composting as this data only shows that urea formaldehyde can be safely used in the compost mix. Moreover, there are many different types of urea formaldehyde with varying degrees of degradability (depending on molecule size), so whenever composting chipboard, a trial period is recommended to validate the method. A search of the literature did not find any evidence of formaldehyde levels in soils to compare to the observed compost residual level, or evidence of bioaccumulation. Formaldehyde alone is unlikely to bioaccumulate as it is reactive and volatile so is likely to break down (ATSDR, 1999)95. Formaldehyde is estimated to have a half-life of 24-168 hours in soil, and has a short residence time in water and air (WHO, 2002)96 so once the urea has broken down and the nitrogen used by the plants the formaldehyde should rapidly breakdown. Seasonal variability Variability in the waste was not observed in the trials, and would not be expected as the material came from one consistent source. Generally wood waste arising vary geographically and seasonally (WRAP, 2002) but no consistent trend has been identified. 6.2.7 Further research Further research • Using different methods of wetting e.g. sprinklers; • Lignin degradation rates; and • Biodegradation analysis of the phenol formaldehyde and melamine formaldehyde in chipboard.


6.3 Medium Density Fibreboard (MDF) In recent years the increased use of medium density fibre board, has shown a corresponding increase in the waste stream, which is likely to continue. Apart from the recycling of a small proportion of MDF off-cuts in the manufacturing process there are few opportunities to recycle MDF, which has stimulated interest in composting the waste material. The chapter describes the results from eight trials Windrow trials Control – Garden waste only Garden waste and MDF DRY 1 Garden waste and MDF DRY 2 Garden waste and MDF WET 1 (MDF soaked prior to mixing/composting) Garden waste and MDF WET 2 (MDF soaked prior to mixing/composting) In-vessel composting Control - Kerbside collected garden and kitchen waste Kerbside collected garden and kitchen waste and MDF DRY 1 Kerbside collected garden and kitchen waste and MDF DRY 2 Kerbside collected garden and kitchen waste and MDF WET 1 (MDF soaked prior to mixing/composting) Kerbside collected garden and kitchen waste and MDF WET 2 (MDF soaked prior to mixing/composting) 6.3.1 Feedstock The feedstock The feedstock was clean MDF waste from the manufacturing process, which arrived as fines. The consistency of the material was ‘light and fluffy’, and was incorporated at a rate of 10% (w/w).

Figure 20 MDF fines

Chemical analysis and incorporation MDF samples were taken prior to the waste arriving on-site to assess its suitability for composting. The MDF contained the main plant nutrients phosphorus, potassium, and nitrogen. Phosphorus and potassium levels were much lower than those observed in garden waste so the MDF was expected to have a slight dilution effect at the proposed incorporation rates. However, nitrogen is the single most important nutrient with respect to plant growth and this was expected to have a positive effect, as it was 4-5 times higher than in garden waste. The levels of heavy metals were low compared to garden waste.


Table 26 MDF Analysis

Determinant Concentration Dry matter (%) 84 Total Nitrogen (%) 4.7 Ammonium nitrogen (mg/kg) <0.1 Organic carbon (%) 58 Phosphorus (mg/kg) 55 Potassium (mg/kg) 455 Copper (mg/kg) 2.2 Zinc (mg/kg) 4.1 Lead (mg/kg) 0.6 Cadmium (mg/kg) 0.1 Mercury (mg/kg) <0.05 Nickel (mg/kg) 0.2 Chromium (mg/kg) 0.7 Formaldehyde (mg/kg) 124

Half of the MDF was pre-soaked in water, prior to mixing, to assess whether this would improve the composting process. This increased the moisture content of the MDF from 15.6% to 62.2%. Table 27 and Table 28 show the chemical and physical analysis. The samples were taken prior to composting but after mixing with the amendment material. The carbon and nitrogen contents are high and the carbon to nitrogen ratios are within the optimum range. Although half of the trials used MDF that had been pre-soaked there appeared to be little difference in the overall moisture content of these trials after mixing. Since only 10% MDF was added the difference between the WET and DRY would not be expected to be greater than 5% providing that the moisture content of the amendment material was similar. However, the overall moisture content of the DRY trials was 61% and of the WET trials 58%. The two different types of trials (WET and DRY) were set up on separate weeks so differences in the moisture content of the amendment material account for the difference.

Table 27 Garden waste and MDF chemical and physical analysis Windrow

controlWindrow

MDF DRY 1Windrow

MDF DRY 2Windrow

MDF WET 1 Windrow

MDF WET 2Average windrow

MDF Compacted bulk density (g/l) 547 248 323 290 304 291 Dry matter (g/kg) 269 408 552 453 476 472 Total nitrogen (g/kg) 11 14 14 14 11 13 Organic carbon (LOI estimate) (%) N/A 35 36 24 32 32 Organic carbon (Tinsley) (%) 19 15 23 22 20 20 C:N ratio N/A 25 26 17 29 24 Formaldehyde (mg/kg) <5 17 26 11 19 18

Table 28 Kerbside collected waste and MDF chemical and physical analysis Tunnel

ControlTunnel

MDF DRY 1Tunnel

MDF DRY 2Tunnel

MDF WET 1

Tunnel MDF WET

2

Average tunnel

MDFCompacted bulk density (g/l) 382 289 355 301 283 307 Dry matter (g/kg) 271 301 287 401 361 338 Total nitrogen (g/kg) 11 13 15 11 13 13 Organic carbon (LOI estimate) N/A 45 45 40 24 39 Organic carbon (Tinsley) 30 30 24 23 22 25 C:N ratio N/A 35 29 36 18 29 Formaldehyde (mg/kg) 2.5 13.5 20.0 29.9 10.7 19.0


6.3.2 Feedstock preparation Particle size reduction The particle size of the MDF did not need to be reduced as it arrived as a fine material. Mixing and wetting Half of the MDF was pre-soaked in water, and additional water periodically added over a 24 hour period. This increased the moisture content from 15.6 to 62.5%. The other half was mixed with amendment material ‘as received.’ The MDF and pre-shredded garden waste was mixed with a bucket loader. The MDF was mixed with the kitchen and garden waste as the latter came out of the shredder. The MDF was not put through the shredder (even though this would have aided mixing) as the material was very light and fluffy and could potentially block machinery. 6.3.3 Composting The waste materials were weighed prior to composting. The MDF mixed with garden waste was composted in windrows (Figure 21), and the MDF mixed with kitchen waste was composted in batch tunnels for one week prior to completion in windrows. In total the material was composted for 12 weeks.

Figure 21 MDF and garden waste composted in windrows

Figure 22 is an example of the overall time temperature profile during in-vessel composting of MDF with kitchen waste (figures for each trial are shown in the Appendix IV). Table 29 below shows the monitoring data for temperature and moisture during windrow composting.

Figure 22 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF DRY 1)


Table 29 Summary temperature and moisture monitoring during the windrow phase of the MDF trials


Date Point 1 Point 2 Point 3 Moisture1

Core (1 metre)

Surface (0.5 metre)

Core (1 metre)

Surface (0.5 metre)

Core (1 metre)

Surface (0.5 metre)

WINDROW MDF DRY 1 MIN 58.6 52.3 55.2 52.3 54.2 52.3 2 MAX 72.2 71.1 73.4 76.6 75.6 63.2 3 AVERAGE 72.2 71.1 73.4 76.6 75.6 63.2 3

WINDROW MDF DRY 2 MIN 56.4 55.2 52.4 55.7 52.3 52.3 2 MAX 72.5 72.5 71.5 76.0 77.1 73.1 3 AVERAGE 64.3 60.3 64.6 61.8 64.1 61.5 3

WINDROW MDF WET 1 MIN 61.2 55.6 63.6 58.7 62.1 58.8 2 MAX 73.6 70.2 73.6 69.9 76.2 69.9 3 AVERAGE 67.5 62.7 68.6 63.1 69.9 63.4 3

WINDROW MDF WET 2 MIN 57.4 47.7 56.8 51.8 53.7 54.3 2 MAX 77.4 68.8 78.4 72.6 79.2 68.5 3 AVERAGE 64.4 57.7 65.8 59.7 65.6 58.7 3

TUNNEL MDF DRY 1 MIN 54.9 51.2 61.6 54.2 60.3 57.5 2 MAX 73.6 71.6 73.6 72.1 78.9 73.8 3 AVERAGE 67.2 60.0 67.9 63.3 69.6 64.5 3

TUNNEL MDF DRY 2 3 MIN 60.1 57.3 60.0 55.6 55.2 53.7 2 MAX 72.2 68.8 71.2 64.6 72.1 69.9 3 AVERAGE 64.8 60.3 65.6 59.3 64.8 60.1 3

TUNNEL MDF DRY 1 MIN 60.1 55.2 60.2 54.2 58.9 52.4 2 MAX 73.3 66.3 71.6 68.8 73.6 65.2 3 AVERAGE 66.0 60.3 65.4 60.3 64.1 57.8 3

TUNNEL MDF WET 2 MIN 60.1 56.1 60.1 55.1 63.1 55.6 2 MAX 75.0 62.3 74.3 60.1 74.6 63.6 3 AVERAGE 67.9 59.2 67.5 57.9 70.3 58.7 3

Notes1 Moisture content key 1 Too wet 2 Near optimum 3 Too dry


6.3.4 Screening The MDF composting trials were weighed before and after composting, and the percentage of product compared to oversize calculated (Table 30). The data shows an approximate mass reduction of 40% during composting, and 70% product compared to oversize. Pre-wetting the MDF appeared to be beneficial to green waste composting, but not tunnel composting. This was probably due to the fact that the kitchen and garden waste feedstock was already high in moisture.

Table 30: Mass balance of MDF trials before and after composting Weight at

start (tonnes)

Weight at end

(tonnes)

Percentage loss (%)

Weight of product less

than 10mm (tonnes)

Weight of oversize (tonnes)

Percentage of oversize

compared to product (%)

Green waste control 78 66 15 46 19 71Control 112 46 59 30 15 67MDF DRY 1 85 40 53 27 12 69MDF DRY 2 86 48 44 32 17 65MDF WET 1 92 63 32 42 20 67MDF WET 2 91 65 28 47 18 72MDF DRY 1 (windrow) 94 68 27 53 16 77MDF DRY 2 (windrow) 93 59 36 41 18 70MDF WET 1 (windrow) 87 43 51 34 9 79MDF WET 2 (windrow) 80 38 52 30 8 79 6.3.5 Product quality General characteristics The product derived from 10% addition of MDF to garden waste was similar to the compost produced from garden waste alone (Table 31). The differences were characterised by a lower bulk density, higher nitrogen and carbon content and much lower conductivity. The differences between the test composts and the controls were less evident for MDF, garden and kitchen waste compost.

Table 31 General characteristics of the compost derived from garden waste and MDF Windrow

Control Windrow

MDF WET 1

WindrowMDF

WET 2

WindrowMDF DRY 1

Windrow MDF DRY 2

AverageWindrow

MDF

Dry matter (g/kg) 660 533 60 543 464 537Bulk density (g/l) 450 334 295 336 314 320Total N (g/kg) 13 18 16 17 18 18Nitrogen % 1.3 1.8 1.6 1.7 1.8 1.8LOI Organic matter 33 52 54 53 55 54Est organic carbon % m/m 19 30 31 31 31 31Ph 8.4 9.5 8.7 9.3 9.6 9.3Carbon to nitrogen ratio 14 17 20 18 18 18Conductivity (μS/cm 20oC) 1540 554 510 616 410 522 Table 32 General characteristics of the compost derived from kerbside collected garden and kitchen waste

and MDF Tunnel

Control Tunnel

MDF WET 1

TunnelMDF

WET 2

TunnelMDF DRY

1

TunnelMDF DRY

2

Average windrow

MDF

Dry matter (g/kg) 630 516 455 545 545 515 Bulk density (g/l) 379 248 339 267 294 287 Total N (g/kg) 19 15 16 17 16 17


Nitrogen % 1.9 1.5 1.6 1.7 1.6 1.7 LOI (organic matter) 53 59 48 45 57 54 Est organic carbon % m/m 30 34 28 26 33 31 ph 9.0 9.6 9.6 9.7 9.6 9.6 Carbon to nitrogen ratio 16 23 18 15 21 20 Conductivity (μS/cm 20oC) 1505 352 499 499 504 464 Nutrients There are sufficient levels of the main plant nutrients nitrogen, potassium, phosphorus and trace nutrients in the test composts to support growth. The concentration of total nitrogen was elevated in the MDF and garden waste compost (Table 33). The average nitrogen concentration in the MDF and kitchen/garden waste compost (Table 34) appeared to be less than the control. The level of ready available nitrogen (ammonium-N and nitrate N) was also low in all test composts. The results would suggest that adding MDF to garden waste up to 10% may further support plant growth, but make little difference to the nitrogen concentration of kitchen and garden wastes. Overall there were less available nutrients in the test composts compared to the controls, due to the lower dry solids content. Some nutrients chloride, potassium, magnesium and calcium were much less available. These were low in the MDF so these nutrients were diluted overall by the addition of MDF. With regard to the total nutrients there was no overall pattern but some nutrients, sulphur and sodium, were much lower in the test composts.


Table 33 Nutrient analysis of the composts derived from MDF with garden or garden and kitchen waste


TunnelControl

WindrowMDF

WET 1

WindrowMDF

WET 2

WindrowMDF

DRY 1

WindrowMDF

DRY 2

Average MDF

TunnelMDF

WET 1

TunnelMDF

WET 2

TunnelMDF

DRY 1

TunnelMDF

DRY 2

AverageMDF

DTPA extractable nutrients Phosphorus (mg/l) 40 52 51 72 79 68 68 27 21 29 24 25Potassium (mg/l) 2370 2965 1280 1390 1870 1270 1453 776 917 1360 1410 1116Magnesium (mg/l) 179 170 119 123 141 118 125 94 107 113 125 110Sodium (mg/l) 138 289 114 104 133 98 112 148 162 213 237 190Sulphur (mg/l) 648 278 38 26 49 28 35 36 43 65 60 51Boron (mg/l) 1.7 3.3 1.2 1.4 1.7 1.4 1.4 1.4 1.5 2.0 2.2 1.8Copper (mg/l) 0.8 64.7 0.6 0.7 0.6 0.5 0.6 1.0 1.0 1.1 0.9 1.0Iron (mg/l) 43 46 35 64 36 33 42 29 33 29 27 30Manganese (mg/l) 9 37 7 16 7 9 10 16 18 15 18 17Zinc (mg/l) 8 11 8 9 10 8 9 10 10 10 12 10.2Molybdenum (mg/l) < 0.1 0.2 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 < 0.1 Water soluble nutrients Boron (mg/l) 0.7 1.7 0.3 0.5 0.5 0.4 0.4 0.5 0.6 0.8 0.8 0.6Molybdenum (mg/l) 0.2 0.3 <0.1 <0.1 0.1 <0.1 0.1 0.1 0.1 0.1 0.1 0.1Ammonium-N (mg/l) 19 110 7 10 8 7 8 8 8 9 8 8Nitrate-N (mg/l) 40 <5 11 < 5 10 < 5 5 < 5 < 5 < 5 < 5 < 5Chloride (mg/l) 793 908 458 420 510 317 426 252 352 345 362 328Potassium (mg/l) 1745 1800 781 730 917 588 754 446 675 675 658 614Magnesium (mg/l) 50 17 7 9 9 5 8 5 6 6 6 6Calcium (mg/l) 299 89 47 47 54 32 45 34 40 51 47 43Na (mg/l) 106 187 90 79 85 58 78 96 115 127 144 121Iron (mg/l) 1.7 6.5 11.7 15.7 12.1 9.6 12.3 5.5 6.8 5.8 5.4 5.8Phosphorus (mg/l) 6.5 24 11 19 16 14 15 9 9 13 11 11Copper (mg/l) < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 < 0.5 <0.5 < 0.5 < 0.5 < 0.5 < 0.5 <0.5Manganese (mg/l) 0.5 0.5 0.2 0.3 0.3 0.3 0.3 0.2 0.3 0.3 0.3 0.3Zinc (mg/l) 0.2 0.5 0.4 0.4 0.4 0.3 0.4 0.3 0.3 0.4 0.4 0.4Sulphur (mg/l) 609 279 39 25 43 23 33 31 63 44 48 47 Total nutrients Phosphorus (mg/kg) DM 2505 3995 2770 2710 3250 3140 2968 2350 2400 2830 2960 2635Calcium (mg/kg) DM 46300 44850 37400 31800 40100 38300 36900 34100 34700 39300 45100 38300Potassium (mg/kg) DM 10400 16900 10700 10400 13100 10700 11225 8450 9310 11900 10400 10015Sodium (mg/kg) DM 639 1450 877 768 897 769 828 1780 1230 1750 1700 1615Manganese (mg/kg) DM 328 305 339 278 295 299 303 376 375 381 463 399



TunnelControl

WindrowMDF

WET 1

WindrowMDF

WET 2

WindrowMDF

DRY 1

WindrowMDF

DRY 2

Average MDF

TunnelMDF

WET 1

TunnelMDF

WET 2

TunnelMDF

DRY 1

TunnelMDF

DRY 2

AverageMDF

Iron (mg/kg) DM 23300 12600 19600 16600 19300 18500 18500 12500 13500 11500 14000 12875Nitrogen (g/100g) DM 1.3 1.9 1.8 1.6 1.7 1.8 1.8 1.5 0.7 1.7 1.6 1.4Sulphur (mg/kg) DM 4980 5840 2340 2170 2660 2360 2383 2280 2890 2790 2720 2670Magnesium (mg/kg) DM 3810 3100 3020 2840 3260 2950 3018 2510 2690 2740 2960 2725Boron (mg/kg) DM 29 42 39 36 44 39 39 38 37 49 48 43Molybdenum (mg/kg) DM 14 4 0.0 0.0 0.6 0.0 0.2 0.0 0.7 0.8 0.8 0.6 Comparison to the Publicly Available Specification for Composted Materials Overall the MDF test composts performed well against the PAS 100 criteria for pathogens, heavy metal and weeds. Five of the eight test composts met the PAS 100 criteria. The remainder failed on physical contaminants; windrow MDF dry 1 because the level of plastic was above 0.25%, tunnel MDF dry 1 and 2 because the overall level of physical contaminants was above 0.5%. However, the majority of this contamination (analysis not shown) was paper. One of these trials (MDF Dry 2) also failed on another criterion – the lead content was higher than permitted - and much higher than in the other composts. The high level of lead observed can be attributed to the green and kitchen waste as it is 3 orders of magnitude lower in the MDF analysis.

Table 34 Comparison of the composts derived from MDF and garden waste or garden and kitchen waste to the PAS 100 Windrow Tunnel

ControlWindrow

MDF WET 1

WindrowMDF

WET 2

WindrowMDF

DRY 1

WindrowMDF

DRY 2

Average

Windrow MDF

TunnelMDF

WET 1

TunnelMDF

WET 2

TunnelMDF

DRY 1

TunnelMDF

DRY 2

Average tunnel

MDF

PAS 100 limit

Stability Compost Stability (mgCO2/gV/d)

5.0 10.8 4.3 8.5 2.4 4.8 5.0 7.5 8.9 13.5 8.7 9.7 16.00

Pathogens Escherichia coli (cfu/g) <10 < 10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 1000Salmonella (/25g) N D N D N D N D N D N D N D N D N D N D N D N D Absent

Heavy metal Total Lead (mg/kg) DM 81 119 95 102 96 108 100 175 140 127 360 201 200Total Nickel (mg/kg) DM 16 13 17 15 18 17 17 16 15 14 15 15 50Total Zinc (mg/kg) DM 203 198 207 248 181 310 237 214 207 227 222 218 400Total Cadmium (mg/kg) DM 0.5 0.8 0.5 0.4 0.5 0.5 0.5 0.6 0.5 0.7 0.7 0.6 1.5Total Chromium (mg/kg) DM 30 21 21 22 30 23 21 23 24 18 19 21 100Total Copper (mg/kg) DM 76 65 40 53 40 43 44 59 70 70 61 65 200Total Mercury (mg/kg) DM 0.2 0.6 0.1 0.1 0.1 0.1 0.1 0.2 0.2 0.1 0.1 0.2 1.0

Plant growth test Percentage germination 102 102 104 104 103 100 103 103 97 97 104 100 80


Windrow TunnelControl

WindrowMDF

WET 1

WindrowMDF

WET 2

WindrowMDF

DRY 1

WindrowMDF

DRY 2

Average

Windrow MDF

TunnelMDF

WET 1

TunnelMDF

WET 2

TunnelMDF

DRY 1

TunnelMDF

DRY 2

Average tunnel

MDF

PAS 100 limit

compared to control Percentage Fresh wt compared to controls

89 92 91 116 97 84 97 112 96 96 102 102 80

Comments/abnormalities Comment1 Comment2 Comment3 Comment4 Comment5 Comment6 Comment7 Comment8 Comment9 Comment10 No abnormalities

Physical contaminants Percentage of glass, metal and plastic over 2mm

0.2 0.7 0.0 0.0 0.4 0.2 0.0 0.0 0.0 4.3 1.4 1.4 0.5

Percentage of plastic over 2mm

0.0 0.0 0.0 0.0 0.4 0.2 0.0 0.0 0.0 0.5 0.47 0.25

Percentage of stones > 4mm 4.5 0.5 2.7 0.0 1.8 2.7 2.0 0.0 0.0 1.1 0.0 0.3 8Total sharps 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0.0

Weeds Weeds No of weeds per litres 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Pass/Fail Pass Fail Pass Pass Fail Pass Pass Pass Fail Fail Pass 1. Windrow control (sample 1) - All mid green. Controls had very slight leaf purpling, test plants. Windrow control (sample 2) - test plants had strong leaf purpling. All

were mid green 2. Tunnel control (sample 1) - All mid green, test plants had strong leaf purpling, Tunnel control (sample 2) - All mid green, slight interveinal chlorosis on some of the oldest

leaves. Test plants had slightly more leaf purpling than the controls 3. All similarly tall and mid green with no leaf purpling 4. All mid green with no purpling 5. All similarly tall and mid-green with no leaf purpling 6. One small test 1 senesced after day 12. Plants mid-green with no purpling 7. All mid green with no purpling 8. Mid green with no purpling 9. All mid green with no purpling 10. All mid green with no leaf purpling


Contaminants outside the scope of PAS 100 The following contaminants were measured in the controls (garden waste or garden waste and kitchen waste) and the composts derived from a 10% MDF inclusion rate: • Arsenic • PAHs • Volatile organic compounds (VOC) • Semi-volatile organic compounds (SVOC) • Polychlorinated bi-phenols (PCBs) • Phenols The levels of all the contaminants were low and comparative to the controls (Table 35), with the exception of formaldehyde covered in the next section.

Table 35 Other contaminants WindrowControl

Windrow MDF

Tunnel MDF

Tunnel control

Total Fluoride (mg/kg) DM 85.0 55.0 62.0 59.0 Total Arsenic (mg/kg) DM 11.0 11.1 7.9 6.8 PAH Naphthalene (mg/kg) Air Dried 2.5 0.5 1.9 4.1 Acenaphthylene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Acenaphtene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Fluorene (mg/kg) Air Dried 0.8 < 0.5 0.4 0.6 Phenanthrene (mg/kg) Air Dried < 0.5 0.4 0.7 Anthracene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Fluoranthene (mg/kg) Air Dried 1.1 0.8 1.0 1.0 Pyrene (mg/kg) Air Dried 1.0 < 0.5 0.4 0.7 Benzo(a)anthracene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Chrysene (mg/kg) Air Dried 0.6 < 0.5 0.4 <0.5 Benzo(b)fluoranthene (mg/kg) Air Dried 0.8 < 0.5 0.4 0.9 Benzo(k)fluoranthene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Benzo(a)pyrene (mg/kg) Air Dried <0.5 < 0.5 0.4 <0.5 Dibenzo(ah)anthracene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Benzo(g,h,I)perylene (mg/kg) Air Dried 0.9 < 0.5 0.8 0.8 Indeno(123-cd)pyrene (mg/kg) Air Dried <0.5 < 0.5 0.4 <0.5 Formaldehyde (mg/kg) 1.3 33.8 15.6 0.9

VOC ANALYSIS (mg/kg) Below detection level 0.1 (see appendix)

SVOC ANALYSIS (mg/kg) Below detection level 1.0 (see appendix)

PCB CONGENERS (mg/kg) Below detection level 0.01 (see appendix)

PHENOLS (mg/kg) Catechol < 0.1 <0.1 <0.1 <0.1 Phenol < 0.1 0.3 0.4 0.1 Cresols < 0.1 0.2 <0.1 <0.1 Xylenols < 0.1 <0.1 <0.1 <0.1 Trimethylphenol < 0.1 <0.1 <0.1 <0.1 Total phenols < 0.5 0.4 0.4 < 0.5

Formaldehyde The levels of formaldehyde were monitored before and after composting. The results (Figure 23) are displayed for each of the trials. Half of the trials, labelled wet, were incorporated with MDF pre-soaked for 24 hours. The other half were not pre-soaked (labelled dry). In the trial using kerbside collected kitchen and garden waste with 10% MDF added, the


formaldehyde behaved as expected, being reduced significantly (almost 50% in the trials using pre-soaked MDF), but only marginally in the trials that were not wetted. The garden waste and MDF trials (composted in windrows only) did not behave as expected. In all four of the garden waste trials the levels of formaldehyde appeared to increase, and in one trial MDF WET 2 (windrow) it appeared to double. This would not have been predicted from the literature. Although the data suggest the level of urea formaldehyde has increased this is not feasible under the conditions observed. The apparent increase is likely to be explained by a combination of factors. The urea formaldehyde may not have broken down despite going through the composting process. The rate of breakdown is dependent on the polymer’s composition – not all urea formaldehyde molecules are the same. Long chain polymers are less soluble, and as a consequence more resistant to breakdown, therefore the urea formaldehyde used in the MDF may have been more resistant to breakdown than the urea formaldehyde observed in the earlier garden waste and chipboard trials. That would at least explain high levels at the end, but not levels higher than at the start, or why the lower final concentrations were observed in the garden, kitchen and MDF waste composted in the batch tunnels. Another likely explanation is sampling error. The garden waste and MDF arrived at the site pre-shredded and was mixed using only a bucket loader. The kitchen and garden waste needed to be shredded on-site which enabled more thorough mixing of smaller volumes of material as they came out of the shredder. Insufficient mixing of the waste could have resulted in a sampling error. An apparent increase in formaldehyde may be partially explained by a greater concentration of MDF fines in the product than in the waste input. The MDF fines are less than 10 ml and passed through the screen into the product, which could result in greater concentration of formaldehyde in the product than in the input material. This, however, can not fully explain. Error in sampling the initial feedstocks, as a result of poor mixing, is the most likely explanation as this was the only process factor that differed. It may, however, have been compounded by some of the other factors explained.


Figure 23 Fate of formaldehyde during composting 10% MDF with garden waste or kerbside collected garden and kitchen waste

0

5

10

15

20

25

30

35

40

45

MDF 1 DRY(Tunnel)

MDF 2 DRY(Tunnel)

MDF WET 1(Tunnel)

MDF WET 2(Tunnel)

MDF WET 1(Windrow)

MDF WET 2(Windrow)

MDF DRY 1(Windrow)

MDF DRY 2(Windrow)

Trial

Form

alde

hyde

con

cent

ratio

n (m

g/kg

)

Initial formaldehyde (mg/kg)Final formaldehyde (mg/kg)


6.3.6 Conclusions Collection The material used on site was collected from the manufacturing process, and reduced to a small particle size for bulk delivery. Analysis of the waste was carried out prior to delivery to determine potential agricultural benefit and safety. Processing The MDF was delivered as a very fine material that was quite ‘fluffy’ and difficult to incorporate evenly. It was mixed after shredding to keep handling to a minimum and prevent blockage of machinery. The temperature achieved during the composting of kerbside collected garden waste and kitchen wastes were sufficient to meet Animal By-product regulations, and overall temperatures in the windrow indicating that composting was progressing adequately. Maximum inclusion rate Ten percent MDF was included in all the trials. The data shows that this did not have any detrimental effect on either the compost quality or the plant growth, nor did formaldehyde affect the plant appearance despite moderately high levels. The mass balance data showed that degradation occurred at this incorporation rate and a similar percentage of product was recovered compared to controls. Benefits and disadvantages Apart from the gate fee the main benefit of incorporating MDF was to increase the nitrogen in the garden waste derived compost, although this was not proved statistically. The nitrogen concentration in the kerbside collected garden and kitchen waste did not measurably increase with the addition of MDF. The MDF material was difficult to handle being a very light material that could be easily blown, and could potentially block machinery. Extra health and safety precautions were needed to prevent exposure to formaldehyde, and if processed on a continuous basis a monitoring programme would be required. Seasonal variability Since the material used on the site was derived from a manufacturing process then seasonal variability was not expected. Wood waste arising are variable but trends have not been established (WRAP, 2002).


6.4 Market waste Food markets produce a high proportion of biodegradable waste which can be segregated at source to enable composting. However, this type of waste is likely to be more difficult to compost than garden waste because it has a high moisture content and is more likely to produce odorous mixtures. In order to assess the practicalities and end product quality the following trials were carried out. Control (kerbside collected garden, kitchen and cardboard) Market waste 1 (Kerbside collected garden, kitchen and cardboard waste with added fruit and vegetable wastes) Market waste 2 (Kerbside collected garden, kitchen and cardboard waste with added fruit and vegetable wastes) 6.4.1 The Feedstocks To fairly represent market waste, this was visually inspected (as shown in Figure 24) at a market. The fruit and vegetable waste from wholesale suppliers, processed at the St Ives Composting site, was then mixed to simulate the market waste observed. The market waste mixture was then mixed with the kerbside collected feedstock.

Figure 24 Market waste

Chemical analysis Immediately after mixing, the feedstock was analysed for a range of properties. The dry matter content (Table 36) 332.5 g/kg was very low for composting. The bulk density was in the normal range, while the C:N ratio was slightly low due to the high nitrogen content of the fruit and vegetable waste. The two samples were comparable in most analyses, except they had markedly different bulk densities, and the carbon content of sample 1 was higher than sample 2, which resulted in a different C:N ratio. This could be explained if sample 1 had a higher carbon content.

Table 36 Analysis of the cardboard trial feedstocks

Sample type In-vessel control

Market waste 1

Market waste 2

Market waste

average Moisture content (%) 62 65 69 68 Bulk density (g/l) 271 260 469 365 total nitrogen (g/kg) DM 11.1 13.2 15.7 14.5 Nitrogen % DM 1.1 1.32 1.57 1.4 Organic carbon %m/m 303 30 22 26 C:N ratio 27.6 23 14 18 Lead (mg/kg) DM 62.0 69.5 62.1 65.9 Nickel (mg/kg) DM 8.1 13.4 9.8 11.6 Zinc (mg/kg) DM 108 136 125 131


Cadmium (mg/kg) DM 0.5 0.5 0.6 0.6 Chromium (mg/kg) DM 16.7 14.8 11.3 13 Copper (mg/kg) DM 34.6 64.1 67.3 65.7 Mercury (mg/kg) DM 0.1 0.2 0.1 0.1

Incorporation rate The main factor limiting the incorporation of fruit and vegetable waste was the moisture content. Due to the odour potential the feedstock had to be dealt with immediately. Therefore, assumptions were made regarding the moisture content rather than reliance on analysis. The fruit and vegetable waste was assumed to be 95% water and kerbside collected waste 55%. Therefore mixing 6 parts garden waste (by weight) to 1 part vegetable waste would give an approximate moisture content of 61%. The data shown in Table 36 gives the actual moisture content of the mixture. This was higher than expected at 67%, indicating that the kerbside collected kitchen waste itself had a high moisture content, approximately 60%.

Table 37 Incorporation rate of the composting mixes Trial

Incorporation rate

In-vessel control (garden and kitchen waste) As received Market waste 1 15% (by weight) Market waste 2 15% (by weight)

6.4.2 Feedstock preparation Particle size reduction The particle size was reduced using a hammer and flails shredder to <6cm. Mixing and wetting The wastes were weighed before mixing as recorded in Table 38. The wastes were then mixed during shredding using a ‘bucket loader.’

Table 38 Weights of the feedstocks added Trial Weight of market

waste (tonnes)

Control As received Market waste 1 20 Market waste 2 24

The feedstocks were not wetted as the moisture content was already high. 6.4.3 Composting process The market waste trials were composted in batch tunnels for one week. Figure 25 and Figure 26 show the time temperature profile during that time. The temperature of the compost was allowed to rise above 60oC, where it was maintained for 48 hours before being cooled down to enable it to be removed. Whilst in the vessel, air is circulated through the material, which is also beneficial in providing oxygen but also in reducing the excessive moisture of the market waste. The data show that even though the moisture content was above the level normally accepted, sufficient temperatures could still be achieved to meet the Animal By-Product Regulations 2003. Composting was then continued in windrows.


Figure 25 In-vessel time and temperature profile of the first market waste trial (market waste 1)


Figure 26 In-vessel time and temperature profile of the second market waste trial (market waste 2)


The table below summarises the windrow temperature achieved during the 8 week period following in-vessel processing. Observation of the moisture content show that the pile was too wet for optimal composting and turning the pile was not sufficient to dissipate the moisture.

Table 39 Temperature and moisture monitoring in windrows after processing in-vessel BATCH TEMPERATURE READINGS

Point 1 Point 2 Point 3 Core (oC) Surface(oC) Core (oC) Surface(oC) Core(oC) Surface(oC) Moisture1

MW1 Min 60 55 59 53 59 52 1 Max 67 63 68 61 70 60 1 Average 63 59 64 58 64 57 1 MW2 Min 55 52 56 50 61 55 1 Max 65 60 56 50 61 55 1 Average 61 58 63 58 64 58 1

Moisture content key 1 Too wet 2 Near optimum 3 Too dry 6.4.4 Screening The final product was screened to <10mm in a McCloskey’s 621 trommel. The data show that there was less weight reduction, and a smaller proportion of sub 10 mm product recovered from the market waste compared to the controls. Analysis later in this report indicates that this was primarily due to the high moisture content compared to the controls making the product more difficult to screen. Further composting would help to dry the compost and increase recovery of the product, even though stability tests indicate that no further treatment is required.

Table 40 Mass analysis of the end product

Weight at start

(tonnes)

Weight at end

(tonnes)

Percentage reduction (%)

Weight of product less than 10 mm

(tonnes)

Weight of oversize (tonnes)


product% (by weight)

Control 112 46 59 30 15 66Market waste 1 137 66 52 35 31 54Market waste 2 140 70 50 44 26 63Market waste Average

139 68 51 40 29 59


6.4.5 Product quality The final product was assessed to determine its characteristics, and hence the most suitable applications. Physical and chemical characteristics The data in Table 41 describes the chemical and physical characteristics of the compost. The compost is still very wet so would have higher transport costs per tonne dry matter. The C:N ratio was relatively high due to a high carbon content, whereas the nitrogen content was similar to the control. In other respects the market waste compost was similar to the controls. However, it had a significantly lower conductivity, similar to the range required in growing media.

Table 41 Physical and chemical characteristics of compost produced from market waste In-

vessel control

Market waste 1

Market waste 2

Average Market waste

Dry matter (g/kg) 630 419 421 420 Bulk density (g/L) 379 319 396 358 Total N (g/kg) DM 18.5 16.0 19.5 17.8 Nitrogen % DM 1.8 1.6 2.0 1.8 LOI (g/100) dry matter 53 64 57 61 Est organic carbon % m/m 30 37 33 35 C:N ratio 16 23 17 20 pH 9.0 9.1 9.0 9.0 Conductivity (μS/cm 20oC) 1505 567 559 563

Nutrients The nutrients that are usually measured by DPTA extraction (phosphorus, magnesium, iron and zinc), were all low compared to the controls (Table 42), consistent with the low conductivity observed in Table 41. The water extractable nutrients, ammonium-N, potassium, and chloride were also low compared to the controls, which is positive as garden waste composts are usually too high in potassium and chloride to support plant growth. The ammonium-N were also high in the control, which could potentially cause toxicity. Nitrate-N was similar to the controls. Overall, the nutrients tended to be lower in the market waste, particularly the more readily available nutrients.

Table 42 Nutrient value of the market waste derived compost compared to controls

In-vessel control

Market waste 1

Market waste 2

Average market waste

DTPA Extractable nutrients Phosphorus (mg/l) 52 30 36 33 Potassium (mg/l) 2965 1020 1330 1175 Magnesium (mg/l) 170 125 144 134.5 Sodium (mg/l) 289 171 234 202.5 Sulphur (mg/l) 278 64.4 84.7 74.6 Boron (mg/l) 3.3 2.1 2.5 2.3 Copper (mg/l) <0.50 0.8 0.9 0.8 Iron (mg/l) 46.4 21.3 30.1 25.7 Manganese (mg/l) 36.5 17.2 11.2 14.2 Zinc (mg/l) 10.8 7.4 10.3 8.86 Molybdenum (mg/l) 0.2 < 0.1 < 0.1 <0.1 Water soluble nutrients Boron (mg/l) 1.72 0.95 1.08 1.02 Molybdenum (mg/l) 0.32 0.14 0.14 0.14 Ammonium-N (mg/l) 110 4 5 5 Nitrate-N (mg/l) <5 < 5 < 5 <5 Chloride (mg/l) 908 345 439 392 Potassium (mg/l) 1800 727 852 790 Magnesium (mg/l) 16.5 8 9 9 Calcium (mg/l) 89 59 63 61


In-vessel control

Market waste 1

Market waste 2


Na (mg/l) 187 117 151 134 Iron (mg/l) 6.5 4.0 3.9 3.96 Phosphorus (mg/l) 24 10 10 10 Copper (mg/l) < 0.50 < 0.5 < 0.5 <0.5 Manganese (mg/l) 0.5 0.3 0.2 0.2 Zinc (mg/l) 0.5 0.6 0.7 0.7 Sulphur (mg/l) 279 59 77 68 Total nutrients Phosphorus (mg/kg) DM 3995 2630 2960 2795 Calcium (mg/kg) DM 44850 40900 32000 36450 Potassium (mg/kg) DM 16900 9750 9370 9560 Sodium (mg/kg) DM 1450 1390 1550 1470 Manganese (mg/kg) DM 461 336 328 332 Iron (mg/kg) DM 12600 9470 16000 12735 Nitrogen (g/100g) DM 1.8 1.6 2.0 1.8 Sulphur (mg/kg) DM 5840 2540 2730 2635 Magnesium (mg/kg) DM 3100 2510 2800 2655 Boron (mg/kg) DM 42. 54 43 48 Molybdenum (mg/kg) DM 4.1 1.6 2.0 1.8

Comparison to the Publicly Available Specification for Composted Materials (PAS 100:2005) The compost derived from market waste met most tests in the PAS 100 specification, with the exception of the plant growth test. The fresh weight of the test plants were only 66% of the weight of the control plants. PAS 100 requires the weight of plants grown in the test compost to be no less than 80% of the controls. The was not caused by a lack of nutrient as the nitrate levels were similar compared to the controls, and although other main plant nutrients including phosphorus and potassium were lower this would not have resulted in the low comparative growth. The test results also show the compost is sufficiently stable indicating that any phytotoxic organic molecules, derived from the fruit, have been broken down. The low growth rate could be attributed to the fact that a high inclusion rate of compost would have been used in the plant growth test because the volume of compost used is dependent on the conductivity, which was low. An alternative explanation is the high moisture content. Heavy metal and physical contamination levels in the market waste were all low compared to the PAS 100 specification, with the exception of stones.

Table 43 Comparison of the market waste composting trials to PAS 100 In-vessel

control Market

Waste 1Market

Waste 2Average market waste

PAS 100 limit

Stability Compost Stability (mgCO2/gV/d) 10.8 10.6 11.9 11.3 16

Pathogens Escherichia coli (cfu/g) <10 <10 <10 <10 1000 Salmonella (/25g) N D ND ND ND Absent

Heavy metals Total Lead (mg/kg) DM 119 69 60 65 200 Total Nickel (mg/kg) DM 13 11 10.0 10 50 Total Zinc (mg/kg) DM 198 154 143 149 400 Total Cadmium (mg/kg) DM 0.8 0.6 0.5 0.5 1.5 Total Chromium (mg/kg) DM 21 11 22 16.8 100 Total Copper (mg/kg) DM 65 54 73 63 200 Total Mercury (mg/kg) DM 0.6 0.1 0.1 0.1 1.0

Plant growth test Percentage germination compared 102 100 100 100 80


In-vessel control

Market Waste 1

Market Waste 2


PAS 100 limit

to control (5) Percentage Fresh wt compared to controls (5)

92 53 76 65 80

Comments Comment 1 Comment 2

Physical contaminants Percentage of glass, metal and plastic over 2mm (%)

0.7 0.0 0.4 0.2 0.5

Percentage of plastic over 2mm 0.0 0.0 0.4 0.2 0.25 Percentage of stones > 4mm (%) 0.5 0 1.5 0.8 8 Total sharps 0.0 0.0 0.0 0.0 0.0

Weeds Weeds No of weeds per litres 0.0 0.0 0.0 0.0 0.0 Pass/fail Fail Fail Fail Fail

Comment 1. The test plants were slightly dark green with very strong leaf purpling and yellowing cotyledons. Very slight inter

veinal chlorosis on all. 2. The test plants were slightly dark green and strong leaf purpling and slight interveinal chlorosis on all. Controls

were mid green with moderate leaf purpling 6.4.6 Conclusion of the market waste composting trials Collection The fruit and vegetable wastes used in the trials were not sourced from a market. However, the method of collection will need to be similar using containers to stop water leakage. Source separation of wastes at the market may or may not be needed depending on the waste produced, and the composting system. For example, fish waste will need to be separated if the facility can not handles ABPR material. Processing The wet nature of the fruit and vegetable waste made it difficult to process, and the waste had potential to be odorous so had to be handled efficiently. Process observations and analysis of the end product indicated that the material was above the optimal moisture content for composting. Comparison of the product with the feedstocks shows the moisture content did reduce during the process but remained above optimal. The reduction in moisture content was less in the market waste compared to the controls despite optimal temperatures being achieved. This indicates that the process should be adapted to assist the drying out of the compost. This could be achieved by retaining the feedstock in-vessel for longer or using a more bulky amendment material e.g. wood chips that would increase porosity. Maximum inclusion rate The data identified moisture content as the limiting factor for optimal composting. In these trials the market waste was mixed at a rate 1 to 6 (by weight) with kerbside collected waste resulting in a moisture content of 68%. This is higher than the 60% normally recommended for composting. Despite this, the material composted adequately but less product was achieved in the end, and the compost failed the bioassay trials. It would therefore be recommended that less than 15% market waste should be added. Benefits and disadvantages The advantage of composting market waste is the generation of income from a feedstock that is readily compostable and clean, which therefore produces a saleable product. The analysis also indicates that the product had a lower conductivity, which is beneficial for growing media applications. The conglomeration of compost particles with a high moisture content resulted in a high proportion of oversize and less product. Low growth rates were observed in the germination trials, but this could not be explained by the nutrient levels or phytotoxic effects, so may have been due to waterlogging. The feedstock also has a high odour potential. Seasonal variability Market waste will vary with season but the effect of this may be masked by the variation in different types of market waste produced each week. The most significant seasonal variation factor is the amendment material. This trial took


part in mid winter when there was a greater proportion of woody material, combined with fruit and vegetable waste. In summer there will be more potential for odour generation as the feedstocks will contain more nitrogenous waste.


7 Conclusions

7.1 The quality of compost from the trials The trial work resulted in compost derived from green waste or green waste and kitchen waste mixed with one of four different waste types – card, chipboard, MDF and market waste. All the compost produced a useable product at 10 mm that was environmentally safe and had sufficient nutrient to support plant growth, but not all were of sufficient quality to meet the PAS 100 criteria. In the trials involving compost derived from mixing cardboard with green and kitchen waste had failed the PAS 100 test due to levels of physical contamination above the PAS 100 criteria. However, this contamination was not directly caused by the increased cardboard content, but a result of plastic packaging being mistakenly put into the collection instead of cardboard or plastic packaging being mistakenly construed as kitchen waste. In addition the laboratories categorised paper as a physical contaminant, which of course, was elevated due to the inclusion of card. This level of contamination means that the compost had to be screened to 10mm rather than a courser fraction, for example >25mm, resulting in a large proportion of oversize material. It can therefore be concluded that to include cardboard in kerbside collections, (and the conclusion may also be applicable to food waste collections) that councils need to direct resource towards specifically educating householders on the segregation of plastic kitchen packaging. The alternative is for producers to invest in separation equipment but this would lead to extra processing costs. The quality of the compost produced from chipboard and MDF was also compared to PAS 100. Like the cardboard trials a minority would not have been able to obtain PAS 100. This was also due primarily to levels of physical contamination not directly attributable to the chipboard or MDF. Organic contaminants outside the scope of PAS 100 were also tested, and were found to be at similar levels to green waste with exception of urea formaldehyde, which is used a fertiliser. Therefore the compost could be used beneficially in agriculture, restoration or blended to produce horticultural products or soil substitutes. However, the compost was not as aesthetically agreeable. The compost made from chipboard had small bits of wood in it making it appear lighter, and MDF compost was more fibrous texture. Since some customers judge compost on how similar it appears to peat or loam, then this may have a negative impact. It can therefore be concluded that that the inclusion of 5-10% MDF or chipboard can be favourable to support plant growth, but this needs to be weighed against the effect on aesthetic quality. The compost derived from green/kitchen waste and market waste failed the PAS 100 growth test. The reason for this is not clear. It would have been expected to perform well against green waste because of the higher nitrogen content, and the low conductivity observed. The low conductivity however would have resulted in a greater ratio of compost to peat in the growth test, which may have contributed, and the moisture content was very high. Otherwise, the characteristics of the compost were suitable to support plant growth.

7.2 The practicalities Overall, composting cardboard, chipboard, MDF or market waste was entirely feasible. However, processing was more challenging than composting green waste or green and kitchen waste alone, in particular chipboard and MDF were much more difficult. The addition of card did not affect composting in terms of biological degradation or achieving temperature. However, in order for the card to compost well then it needed to be wetted at the start, which also required a small particle size. Both shredding and wetting the material were key to composting card. A proportion of the card passed through the shredder intact so a powerful shredder is required to compost card. Composters intending to use chipboard and MDF need to consider the extra processing required. In these trials an extra processing step was required to reduce the size of the chipboard to make it suitable for shredding, and the chipboard was shredding twice. Although there was never any problem maintaining composting temperatures, the chipboard and MDF dried out very quickly despite being wetted before and during composting. Re-wetting with a bowser during the process was not very effective, so re-wetting in a slower and more controlled manner (e.g sprinkler) is likely to be more effective. A large quantity of dust was generated while composting chipboard and MDF. This had mechanical and health and safety implications. The dust blocked radiators in machines, which had to be cleaned out regularly. The large amount of dust generated meant protective clothing had to be worn. Also, formaldehyde was released during processing and if MDF or chipboard are incorporated into composting processes then monitoring would have to be carried out to ensure that personal exposure limits (referred to earlier) are not exceeded.


The high moisture content made the market waste difficult to handle. The waste had potential to be odorous so needed to be process quickly. Sufficient temperatures were achieved to meet time-temperature requirement and composting to proceed. Less product was recovered at the end compared to controls so either a longer period of composting is required to dry out the waste or less market waste should be incorporated.

7.3 Economic viability Whether composting cardboard, MDF, chipboard or market waste is economical to a site will, of course, depend on the circumstances peculiar to that site – including: • Price obtained for the waste; • Capacity compared to waste that is easier or more difficult to process; • Capacity compared to waste that obtains a higher or lower gate fee; • Transport costs; • Processing costs; • Length of contract; and • Capital investment required. The economics of composting green and kitchen waste with cardboard included do not differ greatly from processing green and kitchen waste alone as the incremental increase in the cost of processing more material is covered by the extra gate fee obtained. The trials would suggest that there are areas were extra investment may be required. There is also likely to be a higher volume of over-size material that may require further processing or even disposal. The quantity of oversize may be reduced by investing in a more powerful shredder that could cost in the region of £250,000. In the literature review section the costs for processing wood were estimated at £10-20 per tonne, which is economical compared to green waste. However, the trials involved addition of chipboard or MDF to an existing process, resulting in extra stages and processing costs. The material needed to be shredded prior to being mixed and shredded with the amendment material. In addition the large bits of wood had to be broken up prior to shredding, and the equipment cleaned and unblocked more frequently. Additional water was also need and product testing requirements are likely to increase. It is difficult to put an exact cost on this but it is likely to be an extra £5-6 per tonne. The gate fee obtained for fruit and vegetable waste is similar to green waste, but transports cost are more expensive due to the containers required, and labour required to empty containers. The cost of processing market waste after deliver are also similar to either composting green waste, if incorporated in windrows, or composting catering waste in vessel.

8 Further information

The evidence gathered in the production of this report has been used to produce a guidance document for compost producers that wish to produce compost from cardboard or wood wastes, in particular particle boards like MDF and chipboard. The guidance document is available from the WRAP website.


Appendix I

WASTE AND RESOURCES ACTION PROGRAMME WASTE WOOD COMPOSTING SURVEY 2005

Section 1 – Contact Details Company (if not anonymous) ..................................................................................................... Contact .................................................................................................................................... Location ................................................................................................................................... Email or Telephone no...............................................................................................................

Section 2 – Collection of wood waste 1) Do you receive wood or cardboard waste? Yes/no (delete as applicable) 2) Do you compost wood waste or cardboard? Yes/no (delete as applicable). If no, then what do you do with it? ...............................................................................................................................................

Section 3 – Types sources and quantities of wood waste 1) Please state the quantity and types and wood/cardboard waste that you are composting(please tick

all that are relevant and state quantity) Mixed wood waste .........................tonnes/metres cubed

Mixed Panel boards .........................tonnes/metres cubed

Plyboard .........................tonnes/metres cubed

Chipboard/particle board .........................tonnes/metres cubed

Medium density fibre board .........................tonnes/metres cubed

Orientated strand board .........................tonnes/metres cubed

Hard, medium, soft board .........................tonnes/metres cubed

Corrugated cardboard .........................tonnes/metres cubed

Other cardboard e.g. cereal boxes .........................tonnes/metres cubed

Other (please specify) .........................tonnes/metres cubed

........................................................................................................................


Section 4 – Processing 2) What percentage of wood/cardboard waste do you incorporate with the garden waste for

composting? Wood waste .............................................................(%) Cardboard waste .............................................................(%) 3) If you incorporate wood/cardboard waste with catering waste then what percentage do you include

for composting? Wood waste .............................................................(%) Cardboard wastes .............................................................(%) 4) Do you have to alter your composting practices to accommodate wood or cardboard wastes? ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... 5) Are there any difficulties in composting wood or cardboard wastes? ............................................................................................................................................... ............................................................................................................................................... ............................................................................................................................................... 6) Are there any benefits to the composting process or compost product? ............................................................................................................................................... ............................................................................................................................................... ...............................................................................................................................................

Section 5 – Product and end use 7) Does the compost product meet BSI PAS 100 or any other standard or quality assessment? Yes/no (delete as applicable) If yes, which standard......................................................................................................... 8) What type of composted products incorporating wood or cardboard waste are produced? Mulch

Soil conditioner

Ingredient in topsoil manufacture

Other (please specify) ............................................................................................

9) In which markets are the composted products incorporating wood or cardboard wastes used?


Agriculture

Landscaping

Land restoration


Daily cover

Other (please specify) ......................................................................................... 10) Are there any limitations on using products containing composted wood or cardboard waste ............................................................................................................................................... 11) Are you able to obtain a price for products containing the composted wood or cardboard? Yes/no (delete as applicable). If yes, can you provide an estimate of the price obtained? Wood £.............................................................. Cardboard £..............................................................


Appendix II Temperature data

Table 44 Windrow temperature and moisture monitoring data of the controls BATCH TEMPERATURE READINGS

Date Point 1 Point 2 Point 3 Core Surface Core Surface Core Surface Moisture CONTROL (garden waste) 20-Oct 66.3 55.2 69.1 56.3 70.1 59.3 2 31-Oct 70.2 56.3 72.2 58.8 60.1 56.3 2 9-Nov 66.3 58.2 71.3 59.2 63.6 58.2 2 17-Nov 60.1 56.9 73.2 60.1 75.6 63.2 2 24-Nov 71.1 59 76.6 61.1 76.1 61.9 2 1-Dec 73.4 66.2 78.2 69.9 76.9 60.2 2 8-Dec 72.1 60.9 60.9 62.1 62.3 76.5 2 15-Dec 74.3 66.2 73.1 69.1 69.9 58.2 2 22-Dec 66.1 70.2 72.1 65.6 74.2 69.9 2 29-Dec 70.1 65.4 73.1 66.6 74.6 69.2 2 4-Jan 76.6 60.1 76.6 60.8 72.6 64.2 2 11-Jan 72.2 64.2 73.4 61.1 71.2 62.2 2 18-Jan 2 Min 60.1 55.2 60.9 56.3 60.1 56.3 2 Max 76.6 70.2 78.2 69.9 76.9 76.5 3 Average 69.9 61.6 72.5 62.6 70.6 63.3 CONTROL (kerbside collected garden, kitchen and cardboard waste) 27-Oct 60.3 68.4 55.5 62.1 62.3 72.4 2 3-Nov 57.7 61 51.6 60.9 53.7 65.8 2 9-Nov 66.2 75.5 59'6 63 58.4 66.7 2 17-Nov 68.2 77.4 64.7 75.1 71.4 74.6 2 24-Nov 77 74.5 52.7 60.3 60 63.2 2 1-Dec 66.1 71.4 71.9 78.5 76 78.6 2 8-Dec 71.1 76.7 65.4 74.7 70.1 79.9 2 15-Dec 70.1 67.1 70.2 75.8 72.5 76.9 2 22-Dec 70.9 73.9 60.1 76.8 68.1 76.9 2 29-Dec 69.7 70.9 68.5 72.9 70.6 71.7 2 4-Jan 52.9 56.3 58.8 56.8 58.6 57.1 2 11-Jan 66.1 72.8 67.5 76.9 71.8 70.5 2 18-Jan 69.2 78.0 76.2 76.6 79.9 73.3 2 25-Jan 67.3 71.8 71.4 73.7 70.9 71.7 2 2-Feb 62.1 66.4 65.7 67.3 65.9 68.2 2 9-Feb 61.6 66.2 60.2 66.8 60.7 70.1 2 16-Feb 58.8 62.2 67.6 57.6 62.3 61.1 2 22-Feb 66.4 58.8 69.9 63.2 73.2 60.6 2 24-Mar Min 52.9 56.3 51.6 56.8 53.7 57.1 2 Max 77.0 78.0 76.2 78.5 79.9 79.9 2 Average 65.7 69.4 64.6 68.8 67.0 69.7


Table 45 Temperature and moisture monitoring for the windrow phase of the card trials BATCH TEMPERATURE READINGS Date Point 1 Point 2 Point 3 Core Surface Core Surface Core Surface Moisture1 CARD 1 (kerbside collected garden, kitchen and cardboard waste) 28-Oct 56.1 55.0 62.1 54.1 71.0 60.1 2 3-Nov 69.3 56.2 66.4 58.4 692.0 60.6 2 11-Nov 78.3 66.0 77.7 65.5 78.9 67.5 2 17-Nov 61.9 58.8 58.4 55.2 64.2 57.5 2 24-Nov 68.5 60.5 68.5 57.1 65.7 58.8 2 1-Dec 65.7 58.2 70.1 65.4 68.2 56.2 2 8-Dec 70.1 62.0 74.2 63.1 75.5 66.1 2 15-Dec 60.2 57.9 59.9 58.8 63.1 56.1 2 22-Dec 67.7 60.1 69.1 58.2 63.5 57.6 2 29-Dec 69.5 61.2 66.3 58.8 61.5 55.6 3 4-Jan 70.1 69 70 71.3 68.3 69.8 3 11-Jan 65.2 58.4 71.7 62.1 70.2 60.5 3 18-Jan Screened Min 56.1 55.0 58.4 54.1 61.5 55.6 Max 78.3 69.0 77.7 71.3 692.0 69.8 Average 66.9 60.3 67.9 60.7 120.2 60.5 CARD 2 (kerbside collected garden, kitchen and cardboard waste) 08-Oct 63.2 57.6 63.2 62.6 64.2 61.2 2 15-Nov 61.2 58.8 66.8 63.2 71.2 62.4 2 22-Nov 66.8 61.2 67.2 64.2 74.6 63.2 2 29-Nov 68.8 62.3 66.7 64.9 71.3 61.8 2 6-Dec 69.8 63.6 69.7 61.8 73.2 64.2 2 13-Dec 70.6 61.7 74.6 63.2 74.3 61.9 2 20-Dec 71.1 66.2 73.2 61.3 72.1 63.9 2 28-Dec 69.9 60.9 68.6 63.2 70.4 58.2 2 4-Jan 69.9 66.5 71.3 68.8 66.2 56.2 2 11-Jan 71 64.2 69.8 66.2 64.3 52.3 2 18-Jan 68.9 63.7 67.3 64.2 56.3 51.2 2 25-Jan 65.2 56.2 63.2 58.4 66.2 54 2 2-Feb 67.2 58.3 62.1 59.2 63.2 56.7 2 9-Feb 66.1 56.8 63.5 61 68.2 61.2 2 16-Feb 58.6 53.2 60.1 45.8 58.7 48.4 2 22-Feb 55.3 45.8 59.5 55.2 68.40 46.8 2 3-Mar 57.5 48.7 58.9 56.9 59.9 48.9 2 9-Mar 56.7 45.2 57.2 50.8 59.8 48.5 2 16-Mar 55.9 44.8 56.3 52.1 55.9 49.3 2 25-Mar Screened Min 55.3 44.8 56.3 45.8 55.9 46.8 Max 71.1 66.5 74.6 68.8 74.6 64.2 Average 64.9 57.7 65.2 60.2 66.2 56.3

CARD EXTRA 1 (kerbside collected garden, kitchen and cardboard waste, plus 5% extra card) 11-Nov 58.3 55.2 60.1 56.6 64.6 53.2 2 18-Nov 59.8 56.2 63.6 58.9 66.1 60.1 2 25-Nov 63.2 58.8 72.6 59.3 76.8 61.3 2 2-Dec 64.6 60.1 71.8 62.2 71.2 60.9 2 9-Dec 68.8 62.3 68.9 61.7 73.6 63.2 2 16-Dec 63.2 61.7 69.3 64.2 67.3 64.6 2


BATCH TEMPERATURE READINGS Date Point 1 Point 2 Point 3 Core Surface Core Surface Core Surface Moisture1 23-Dec 66.6 60.9 67.6 61.2 70.1 63.2 2 30-Dec 69.9 64.2 70.3 67.2 71 66.4 2 6-Jan 60.1 56.3 66.2 62.3 68.8 61.2 2 13-Jan 66.1 58.9 65.8 64.2 64.6 61.9 2 20-Jan Screened Min 58.3 55.2 60.1 56.6 64.6 53.2 Max 69.9 64.2 72.6 67.2 76.8 66.4 Average 64.1 59.5 67.6 61.8 69.4 61.6 CARD EXTRA 2 (kerbside collected garden, kitchen and cardboard waste, plus 5% extra card) 15-Nov 60.7 53.4 68.8 68.7 64.2 59.1 2 22-Nov 63.6 58.2 64.6 58.1 59.3 60.5 2 29-Nov 62.3 60.3 67.7 56.3 63.2 56.8 2 6-Dec 64.2 61.3 65.5 58.4 64.2 58.6 2 13-Dec 66.5 63.2 68.7 54.7 65.7 57.2 2 20-Dec 68.8 61.3 66.5 58.3 64.2 57.0 2 28-Dec 71.2 62.4 68.4 58.4 61.1 56.8 2 4-Jan 63.3 60.1 64.9 56.2 63.4 56.4 2 11-Jan 68.9 58.4 67.6 56.4 63.2 55.7 2 18-Jan 64.5 58.6 66.3 55.8 65.6 55.2 2 26-Jan 66.8 52.4 65.4 55.6 62.3 55.6 2 2-Feb 62.5 50.1 64.8 54.5 63.2 54.2 2 9-Feb 58.1 48.8 63.2 53.1 61.8 53.6 2 16-Feb 59.6 46.7 62.8 54.2 62.8 54.8 2 23-Feb 57.8 45.2 61.8 55.8 63.20 55.4 2 2-Mar 57.7 44.5 61.2 54.2 61.8 54.3 2 9-Mar 56.8 45.8 58.8 56.1 60.4 52.3 2 16-Mar 55.8 44.2 56.7 48.7 58.3 49.7 2 25-Mar Min 55.8 44.2 56.7 48.7 58.3 49.7 2 Max 78.3 78 77.7 78.5 692 79.9 2 Average 62.7 54.2 64.7 56.3 62.7 55.7 Moisture content 1 Too wet 2 Near optimum 3 Too dry


Table 46 Temperature and moisture monitoring of the windrow phase of the chipboard trials BATCH TEMPERATURE READINGS

Date Point 1 Point 2 Point 3 Core Surface Core Surface Core Surface Moisture

CHIP 1 (garden waste and chipboard) 26-Oct 67.7 71.2 60.9 73.2 67.6 71.1 3 3-Nov 69.9 73.3 62.6 71.6 67.2 70.1 3 9-Nov 69.2 70.3 61.1 70.3 62.2 68.8 3 17-Nov 63.2 69.9 66.2 68.2 61.1 63.6 3 24-Nov 64.6 68.8 66.3 70.2 68.8 73.6 3 1-Dec 59.2 66.3 60 63.2 61.1 64.2 3 8-Dec 58.9 60.1 60 62.6 59.2 60.3 3 15-Dec 57.6 63.2 68.2 66.2 62.6 66.1 3 22-Dec 63.6 62.6 64.6 62.1 61.1 64.7 3 29-Dec 64.6 67.6 60.6 62.6 58.2 61.2 3 4-Jan 66.2 67.2 58.9 63.6 59.9 60.2 3 11-Jan 61.2 65.7 67.2 70.1 60.9 58.2 3 18-Jan 63.7 68.8 66.3 73.1 67.6 56.2 3 25-Jan 60.2 61.1 57.6 62.6 60.1 55.2 3 2-Feb 60.2 63.6 64.6 66.2 60.3 53.2 3 9-Feb 58.2 61.6 57.6 60.0 60.1 52.6 3 16-Feb 59.9 62.6 58.8 60.1 60.8 54.6 3 22-Feb 56.2 63.1 60.2 66.3 61.1 54.8 3 28-Feb 59.9 60.6 58.9 61.6 64.2 56.2 3 9-Mar 3 25-Mar 54.3 46.6 57.0 56.7 57.0 57.9 3 Min 54.3 46.6 57.0 56.7 57.0 52.6 Max 69.9 73.3 68.2 73.2 68.8 73.6 Average 61.9 64.7 61.9 65.5 62.1 61.1 CHIP 2 (garden waste and chipboard) 20-Oct 71.1 60 66.3 56.2 61.1 53.1 2 31-Oct 66.2 58.1 60 56.7 65.2 58.2 2 9-Nov 61.3 58.8 60.3 58.1 66.3 59.9 2 17-Nov 60.1 56.2 58.8 55.5 63.4 63.2 2 24-Nov 74.8 60.5 73.5 62.1 68.4 60 2 1-Dec 69.7 59.2 71.1 61.1 67.2 62.3 2 8-Dec 70.1 61 71.1 61.2 69.1 60.6 2 15-Dec 72.3 66.2 76.4 63.1 65.1 67.1 2 22-Dec 79.9 67.7 72.2 69.9 72.4 65.6 2 29-Dec 74.3 66.2 74.6 65.8 69.5 66.9 2 4-Jan 71.2 64.7 73.6 62.1 71.1 66.6 3 11-Jan 74.2 69.9 70.2 60.2 69.4 67.2 3 18-Jan 68.4 58.4 69.4 58.2 68.7 61.2 3 25-Jan 63.5 56.3 69.5 56.3 65.4 56.8 3 2-Feb 66.8 54.2 68.7 54.2 66.4 61.5 3 9-Feb 62.6 57.6 66.9 55.2 65.8 59.9 3 16-Feb 60.1 52.4 62.5 54.7 62.8 57.3 3 22-Feb 58.6 54.8 63.8 53.8 61.9 51 3 28-Feb 58.8 56.4 61.5 54 69.4 55.2 3 9-Mar 3 25-Mar 41.8 41.9 38.6 37.7 39.2 39.5 3 Min 41.8 41.9 38.6 37.7 39.2 39.5


Max 79.9 69.9 76.4 69.9 72.4 67.2 Average 67.6 59.9 67.9 58.9 66.8 60.7 TUNNEL CHIP1 (garden waste, kitchen, cardboard and chipboard) 28-Oct 62.8 61.3 74.1 71.9 55.1 70.6 3 3-Nov 64.9 41.1 61.2 41.2 58.3 43.5 3 11-Nov 64.7 73.1 56.2 69.3 61.5 72.5 3 17-Nov 62.5 68.9 66.3 58.1 61.5 68.4 3 24-Nov 73.2 68.7 74.4 65.4 73.9 64.5 3 1-Dec 75.5 63.3 75.9 65.1 71.1 64.1 3 8-Dec 74.3 64.3 72.5 59.8 68.5 58.5 3 15-Dec 68.7 66.4 69.9 58.1 67.8 66.1 3 22-Dec 58.4 69.1 58.5 73.2 60.5 55.8 3 29-Dec 66.8 49.0 54.8 58.5 53.8 51.6 3 4-Jan 70.1 65.8 68.8 67.9 56.7 51.0 3 11-Jan 75.7 68.2 66.2 58.6 73.7 56.3 3 18-Jan 66.2 47.1 64.5 52.6 68.1 50.1 3 25-Jan 74.3 62.5 67.5 58.0 69.5 57.1 3 2-Feb 69.1 66.6 66.2 58.8 68.8 57.2 3 9-Feb 58.1 62.7 69.5 54.2 71.3 72.1 3 16-Feb 62.5 50.0 67.4 56.7 71.4 56.8 3 22-Feb 62.0 60.6 68.1 60.5 76.1 68.5 3 25-Mar 50.6 52.3 50.2 49.9 52.1 55.8 3 Min 50.6 41.1 50.2 41.2 52.1 43.5 Max 75.7 73.1 75.9 73.2 76.1 72.5 Average 66.3 61.1 65.9 59.9 65.2 60.0 Chip tunnel 2 (garden waste, kitchen, cardboard and chipboard) 17-Mar 68.3 60.5 73.8 68.8 74.5 68.4 24-Mar 64.5 52.1 68.2 63.5 70.2 58.1 31-Mar 74.1 66.5 70.2 55.6 73.0 64.4 7-Apr 72.7 66.7 74.4 73.4 72.0 67.1 14-Apr 70.4 61.8 64.4 53.5 65.5 50.1 21-Apr 69.2 60.1 71.4 69.9 71.1 60.3 28-Apr 64.6 58.2 67.6 62.3 68.8 59.2 5-May 74.5 57.8 74.8 71.1 66.1 62.7 12-May 71.4 63.3 71.9 68.2 71.6 63.4 19-May 65.2 61.7 60.2 58.4 60.1 55.1 26-May 48.8 46.2 65.8 58.8 57.5 55.6 2-Jun 58.2 56.8 62.5 57.4 60.7 55.1 Min 48.8 46.2 60.2 53.5 57.5 50.1 Max 74.5 66.7 74.8 73.4 74.5 68.4 Average 66.8 59.3 68.8 63.4 67.6 60.0 Moisture content 1 Too wet 2 Near optimum 3 Too dry


Table 47 Temperature and moisture monitoring during the windrow phase of the MDF trials


Date Point 1 Point 2 Point 3 Core Surface Core Surface Core Surface WINDROW MDF DRY 1 (garden waste and MDF) 30-Mar 66.3 55.2 69.1 56.3 70.1 59.3 2 6-Apr 71.1 60 66.3 56.2 61.1 53.2 2 13-Apr 70.2 56.3 72.2 58.8 60.1 56.3 2 20-Apr 66.2 58.1 60 56.7 71.1 58.2 2 27-Apr 60.1 56.9 73.2 60.1 75.6 63.2 2 4-May 60.1 56.2 58.8 55.5 71.8 63.2 3 11-May 59 71.1 61.1 76.6 61.9 58.8 3 18-May 68.2 57.3 60.2 57.3 60.2 56.3 3 25-May 72.2 64.2 73.4 62.2 63.5 58.2 3 1-Jun 63.6 60.2 66.2 64.6 63.2 60.3 3 8-Jun 63.2 57.6 68.2 66.2 66.1 62.6 3 15-Jun 61.6 58.2 60 57.6 62.6 60.1 3 22-Jun 63.6 57.6 58.2 57.3 58.7 55.2 3 29-Jun 60.1 52.3 57.4 52.3 56.5 52.3 3 6-Jul 58.6 52.3 55.2 53.2 54.2 52.7 3 13-Jul 59.0 55.2 60.2 57.3 60.2 56.3 3 WINDROW MDF DRY 2 (garden waste and MDF) 30-Mar 70.2 63.1 69.3 58.2 60.7 58.4 2 6-Apr 61.2 59.9 63.6 58.7 66.1 61.2 2 13-Apr 60.7 56.6 60.2 57.3 70.8 58.2 3 20-Jan 69.9 57.6 71.1 56.2 62.3 58.8 3 27-Apr 72.5 65.5 71.2 68.6 77.1 69.5 3 4-May 65.1 58.1 66.2 63.1 64.6 71.1 3 11-May 67.2 60.9 71.5 66.5 73.7 71.1 3 18-May 69.4 64.3 70.4 66.1 71.5 67.5 3 25-May 64.0 59.2 70.1 67.0 72.0 67.9 3 1-Jun 56.4 61.6 52.4 61.7 52.5 54.7 3 8-Jun 72.1 72.5 66.9 76 64.7 73.1 3 15-Jun 56.5 61.7 54.8 57.6 52.3 52.4 3 22-Jun 68.1 57.5 58.2 55.7 60.1 52.3 3 29-Jun 58.8 56.2 66.1 61.9 55.8 52.3 3 6-Jul 57.0 55.2 62.1 57.2 60 58.4 3 13-Jul 60.0 55.3 59.1 56.2 61.1 57.6 3 WINDROW MDF WET 1 (garden waste and MDF) 11-Apr 61.2 59.9 63.6 58.7 66.1 61.2 2 18-Apr 71.1 63.2 69.8 60.1 65.6 66.2 2 25-Apr 70.2 55.6 63.6 62.7 73.3 69.9 2 2-May 62.3 66.1 68.8 60.2 67.7 63.2 3 9-May 69.9 70.2 73.2 69.9 68.8 59.9 3 16-May 63.6 60.2 73.6 69.2 76.2 58.8 3 23-May 65.6 61.1 71.1 59.9 68.8 62.6 3 30-May 68.2 63.6 71.9 63.2 69.8 60.2 3 6-Jun 63.6 64.2 72.6 60.1 73.2 61.7 3 13-Jun 68.9 60.2 68.7 63.6 72.1 58.9 3 20-Jun 67.6 62.2 66.3 59.3 62.1 60.9 3 27-Jun 71.2 68.3 69.9 67.6 69.8 69.8 3


4-Jul 73.6 61 63.6 62.6 71.6 66.3 3 11-Jul 68.2 61.9 63.6 66.3 72.8 67.6 3 WINDROW MDF WET 2 (garden waste and MDF) 12-Apr 58.1 51.4 56.8 51.8 53.7 54.3 2 19-Apr 65 54.7 65.5 52.8 62.9 59.4 2 26-Apr 68.7 60.5 73.4 60.3 69.2 54.7 3 3-May 59.1 53.5 60.2 57 58.8 59.4 3 10-May 69.4 59 72.5 61.1 69.8 62.9 3 17-May 59.5 47.7 64.4 62.6 71.5 65.2 3 24-May 77.4 68.8 78.4 72.6 79.2 68.5 3 31-May 69.0 62.2 67.1 62.5 68.2 58.8 3 7-Jun 73.5 64.3 72 66.4 73.5 54.9 3 14-Jun 73.0 63.8 62 59.5 68.2 58.2 3 21-Jun 62.2 58 62.1 57.8 61.2 57.1 3 28-Jun 57.4 54.4 57.0 54.6 61.2 57.4 3 5-Jul 58.1 55.8 64.7 58.6 67.8 57.5 3 12-Jul 57.4 56.2 68.9 61.5 58.9 55.5 3 19-Jul 57.5 54.6 61.5 56.1 59.2 56.2 3 TUNNEL MDF DRY 1 (kerbside collected garden, kitchen and cardboard plus MDF) 03-Apr 68.9 62.6 69.9 67.7 70.2 66.2 2 10-Apr 71.1 60.6 63.6 72.1 68.6 71 2 17-Apr 73.6 58.8 72.6 61.6 61.2 67.6 2 24-Apr 68.8 71.6 73.6 69.9 68.8 63.6 3 1-May 63.6 62.1 66.8 59.9 69.6 62.1 3 8-May 68.9 52.3 61.6 55.5 72.6 59.9 3 15-May 73.6 59.9 68.8 60.1 69.9 62.1 3 22-May 54.9 51.2 70.1 65.6 67.2 61.3 3 29-May 68.9 62.6 69.9 67.7 67.6 62.1 3 5-Jun 71.1 60.6 63.6 72.1 73.2 63.7 3 12-Jun 63.6 58.8 72.6 61.6 71.1 73.8 3 19-Jun 68.8 71.6 73.6 69.9 78.9 60.7 3 26-Jun 63.4 62.1 66.8 59.9 69.9 71.6 3 3-Jul 68.9 52.3 61.6 55.5 73.5 61 3 10-Jul 65.7 59.9 68.8 60.1 71.6 67.6 3 17-Jul 61.2 52.3 62.6 54.2 60.3 57.5 3 TUNNEL MDF DRY 2 (kerbside collected garden, kitchen and cardboard plus MDF) 24-Apr 72.2 61.6 71.2 60.2 72.1 69.9 2 1-May 64.6 58.6 68.8 55.6 69.2 59.4 3 8-May 69.9 62.1 66.3 64.6 69.9 63.2 3 15-May 68.8 66.2 69.3 61.6 68.2 64.6 3 22-May 70.0 68.8 68.8 58.8 63.6 59.2 3 29-May 63.6 58.2 61.6 56.8 62.6 58.8 3 5-Jun 61.1 57.6 62.6 60.1 63.6 58.9 3 12-Jun 64.6 57.3 66.2 60.3 63.2 57.6 3 19-Jun 61.6 57.6 60.0 58.8 63.6 57.7 3 26-Jun 62.6 58.8 69.9 60.8 63.6 60.1 3 3-Jul 63.1 60.2 66.3 61.1 64.6 56.6 3 10-Jul 60.6 58.9 61.6 55.8 63.6 61.2 3 17-Jul 60.1 58.2 60.1 56.9 55.2 53.7 3 TUNNEL MDF WET 1 (kerbside collected garden, kitchen and cardboard plus MDF)

17-Apr 73.3 62.6 71.6 67.2 70.1 65.2 2 24-Apr 70.3 61.1 70.3 62.2 68.8 60.1 2


1-May 69.9 66.2 68.2 61.1 63.6 58.4 2 8-May 68.8 66.3 70.2 68.8 73.6 62.3 2 15-May 66.3 60 63.2 61.1 64.2 59.2 3 22-May 61.6 59.7 64.6 60.2 62.2 56.2 3 29-May 60.1 58.2 62.6 59.2 60.3 55.2 3 5-Jun 68.2 63.6 66.2 62.6 66.1 57.3 3 12-Jun 62.6 59.1 62.1 55.7 64.7 57.9 3 19-Jun 67.6 60.6 62.6 58.2 61.2 56.2 3 26-Jun 67.2 58.9 63.6 59.9 60.2 52.4 3 3-Jul 65.7 55.2 67.2 54.2 60.1 58.9 3 10-Jul 60.2 56.6 63.2 57.9 63.4 54.3 3 17-Jul 62.3 56.7 60.2 55.2 58.9 55.2 3 TUNNEL MDF WET 2 (kerbside collected garden, kitchen and cardboard plus MDF) 10-Apr 70.2 59.3 71.6 55.2 71.6 59.2 2 17-Apr 71.2 58.6 74.3 56.6 69.9 58.2 2 24-Apr 69.8 56.2 71.1 58 68.8 57.7 2 1-May 62.6 58.3 70.1 59.9 74.2 60.6 2 8-May 75.0 59.9 70.1 60 70.3 58.8 2 15-May 73.1 60.2 69.8 59.6 73.4 55.6 2 22-May 63.8 61.6 64.6 58.9 70.2 63.6 3 29-May 70.1 62.3 65.2 60.1 66.8 57.9 3 5-Jun 68.2 59.8 70.1 58.2 74.6 59.7 3 12-Jun 66.1 59 68.8 56.2 70.1 59.0 3 19-Jun 70.1 56.1 62.2 55.1 70.8 56.3 3 26-Jun 66.8 59.8 66.3 59.2 73.8 58.8 3 3-Jul 63.4 59.2 60.8 57.6 66.6 58.8 3 10-Jul 60.1 58.2 60.1 56.6 63.1 57.7 3

Table 48 Temperature and moisture monitoring during the windrow phase of the market waste trials BATCH TEMPERATURE READINGS

MARKET WASTE 1 (kerbside collected garden, kitchen and cardboard plus market waste) Date Point 1 Point 2 Point 3

Core Surface Core Surface Core Surface Moisture1 5-Jan 60.1 55.2 59.1 55.6 58.8 55.7 1 11-Jan 62.3 58.8 63.6 53.2 60.1 52.3 1 18-Jan 62.7 56.3 61.6 58.2 61.1 55.6 1 26-Jan 61.2 58.8 63.2 60.2 62.3 56.3 1 2-Feb 66.2 59.3 61.7 59.3 60.2 58.6 1 9-Feb 61.4 58.8 67.2 60.1 66.2 60.1 1 16-Feb 67.3 61.7 63.8 61.2 69.9 59.9 1 23-Feb 65.5 62.6 67.8 60.1 63.6 58.5 1 2-Mar 65.6 58.2 66.2 58.8 66.9 57.4 1 9-Mar 64 57.9 67.4 57.4 70.1 55.4 1 16-Mar 62 56.2 66.1 56.4 68.1 56.8 1 25-Mar Screened Min 60.1 55.2 59.1 53.2 58.8 52.3 Max 67.3 62.6 67.8 61.2 70.1 60.1 Average 63.5 58.5 64.3 58.2 64.3 57 MARKET WASTE 2 (kerbside collected garden, kitchen and cardboard plus market waste) 5-Jan 60.1 55.2 59.1 55.6 58.8 55.7 1 11-Jan 62.3 58.8 63.6 53.2 60.1 52.3 1 18-Jan 62.7 56.3 61.6 58.2 61.1 55.6 1


26-Jan 61.2 58.8 63.2 60.2 62.3 56.3 1 2-Feb 66.2 59.3 61.7 59.3 60.2 58.6 1 9-Feb 61.4 58.8 67.2 60.1 66.2 60.1 1 16-Feb 67.3 61.7 63.8 61.2 69.9 59.9 1 23-Feb 65.5 62.6 67.8 60.1 63.6 58.5 1 2-Mar 65.6 58.2 66.2 58.8 66.9 57.4 1 9-Mar 64 57.9 67.4 57.4 70.1 55.4 1 16-Mar 62 56.2 66.1 56.4 68.1 56.8 1 25-Mar Screened Min 60.1 55.2 59.1 53.2 58.8 52.3 Max 67.3 62.6 67.8 61.2 70.1 60.1 Average 63.5 58.5 64.3 58.2 64.3 57.0 Moisture content 1 Too wet 2 Near optimum 3 Too dry


Appendix III - Protocols

This section sets out details of the project trials, the sampling protocols and analysis protocols for the project.

The trials

The trials shall be carried out at the ENVAR Composting site at St Ives on

Cardboard Chipboard MDF Market wastes

8.1 Sourcing materials

Garden and kitchen wastes that are usually composted as part of the commercial operation shall be used for the trials that involve catering wastes.

Garden waste may be sourced from local sites where extra is needed to begin trials concurrently The wood wastes used for the trials shall be sent for analysis and a visit to the wood producing site

arranged in order to ensure that the wood is suitable for composting

8.2 Compost processing 8.3 Particle size reduction

The particle size shall be reduce to 6 cm in diameter using a Menart P180M hammer and flails shredder to meet the Animal By-Product Regulations 2003 (SI 2003/1482). The same size shall also used for the garden waste trials

8.4 Weighing, mixing and wetting

The materials shall be weighed using a tractor and trailer or the materials kept separate after they are weighed on arrival.

The cardboard trials will be wetted immediately before composting Additional cardboard shall be wetted after mixing The chipboard shall be wetted after mixing 50% of the MDF trials shall be wetted before mixing and 50% after mixing The feedstocks will be mixed using a bucket loader to estimate the required volumes. If the material is

difficult to mix the materials will be added to the shredder to use the shredder action to aid mixing.

8.5 Experimental design

The trials shall be carried out in duplicate The percentage of the test feedstock to be added is shown in brackets


Table 49 Experimental treatments Tunnel control (kitchen, garden and card)

Windrow control (garden waste)

Cardboard 1 (as received) Cardboard 2 (as received) Cardboard extra 1 (5% extra) Cardboard extra 2 (5% extra) Chipboard (5%) Chipboard (10%) Chipboard (5%) Chipboard (10%) Market 1 (20%) Market 2 (20%) MDF WET (10%) MDF WET (10%) MDF WET (10%) MDF WET (10%) MDF DRY (10%) MDF DRY (10%) MDF DRY (10% MDF DRY (10%

8.6 Sampling and Analysis

All feedstocks will be analysed for carbon, nitrogen, dry matter and bulk density Wood based feedstocks will also be analysed for formaldehyde Cardboard feedstocks will be analysed for heavy metals The final products will be analysed (Table 50) according to the schedules in PAS 100 In addition, the wood based composts will be analysed for formaldehyde, arsenic, fluoride, phenols,

PCBS, PAHs, VOCs and SVOCs

Table 50: The Analysis required by PAS 100

Analysis 1 - PAS 100

• E. Coli and Salmonella spp. • PTEs including Cd, Cr, Cu, Pb, Hg, Ni, Zn • Physical contaminants and particle size distribution • Bioassay for phytotoxins and weed progagules • Stability • Total nitrogen • Carbon • Bulk density • Moisture • pH (water extract) • Electrical conductivity (water extract) • Water extractable: chloride, ammonium-N, nitrate – N, P, K, CA, Mg, S, Na , Mn, Fe,

B, Mo, Cu, and Zn • DTPA/Calcium chloride extractable: P, K, Mg, S, Na, As, Cr, B, Fe, Mn, Mo, Cu, and

Zn. • Total: P, K, Mg, Ca, S, Na, Mn, Fe, As, Cr, Cu, B and Mo

The proportion of oversize in relation to the product will also be weighed. A mass balance will be carried out, and visual assessment of the oversize material.

8.7 Sampling methods

Feedstocks shall be sampled to the same principles as BS: 12579-2000 Soil Improvers and Growing media: Sampling Methodology but the material will not be screened

Samples of the finished compost will be taken using a methodology based on BS: 12579-2000 Soil Improvers and Growing media: Sampling Methodology. A cleaned spade will be used to collect a minimum of 12 separate representative sub-samples which will then be combined and thoroughly mixed. The material will be sampled after screening through a 10 mm mesh. The volume of each final sample will be 15 litres for the PAS 100 test, or a minimum of 5 litres for other tests. The sample


will be placed in a sterile polythene bag and sent to an accredited laboratory for analysis. The bag will be labelled with the date of sampling, sample type, and unique identification number using permanent marker and a tie-on label.

The samples will be sent to Eurofins, who are approved to carry out PAS 100 testing.


Appendix IV – Time temperature profiles

Figure 27 Scan of the in-vessel time-temperature profile computer print out of the Tunnel Control


Figure 28 Scan of the in-vessel time-temperature profile computer print out of the CARD 1 trials


Figure 29 Scan of the in-vessel time-temperature profile computer print out for the CARD 2 trial


Figure 30 Scan of the in-vessel time-temperature profile computer print out for the EXTRA CARD 1 trial


Figure 31 Scan of the in-vessel time-temperature profile computer print out for the EXTRA CARD 2 trial


Figure 32 Time and temperature profile of the Tunnel Chip 1 (kerbside kitchen, garden and chipboard)


Figure 33 Time and temperature profile of the Tunnel Chip 2 (kerbside kitchen, garden and chipboard)


Figure 36 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF WET 2)


Figure 37 Time and temperature profile of garden, kitchen waste and 10% MDF (TUNNEL MDF WET 2)


Figure 38 Scan of the time and temperature profile of the first market waste trial (market waste 1)


Figure 39 Scan of the time and temperature profile of the second market waste trial (market waste 2)


Table 51: Non PAS 100 compost contaminants in the chipboard trials Windrow

ControlGarden

waste and chip

Tunnel control

Tunnel chip

Total Fluoride (mg/kg) DM 85.0 85.0 59.0 43.0 Total Arsenic (mg/kg) DM 11.0 10.3 6.8 5.8 PAH Naphthalene (mg/kg) Air Dried 2.5 3.0 4.1 6.0 Acenaphthylene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Acenaphtene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Fluorene (mg/kg) Air Dried 0.8 0.5 0.6 0.9 Phenanthrene (mg/kg) Air Dried <0.5 0.6 0.7 0.6 Anthracene (mg/kg) Air Dried < 0.50 < 0.5 <0.5 < 0.5 Fluoranthene (mg/kg) Air Dried 1.1 1.4 1.0 0.7 Pyrene (mg/kg) Air Dried 1.0 1.2 0.7 0.5 Benzo(a)anthracene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Chrysene (mg/kg) Air Dried 0.6 0.7 <0.5 < 0.5 Benzo(b)fluoranthene (mg/kg) Air Dried 0.8 1.1 0.9 0.9 Benzo(k)fluoranthene (mg/kg) Air Dried < 0.5 0.5 <0.5 < 0.5 Benzo(a)pyrene (mg/kg) Air Dried <0.5 0.8 <0.5 < 0.5 Dibenzo(ah)anthracene (mg/kg) Air Dried < 0.5 < 0.5 <0.5 < 0.5 Benzo(g,h,I)perylene (mg/kg) Air Dried 0.9 0.9 0.8 0.8 Indeno(123-cd)pyrene (mg/kg) Air Dried <0.5 0.6 <0.5 < 0.5 PAH Screen (mg/kg) 10 12 10.5 12 Formaldehyde (mg/kg) 1.3 39.2 0.9 25.3

VOC ANALYSIS (mg/kg) 11-dichloroethene < 0.1 < 0.1 < 0.1 < 0.1 dichloromethane < 0.1 < 0.1 < 0.1 < 0.1 trans-12-dichlororethane < 0.1 < 0.1 < 0.1 < 0.1 2,2-dichloropropane < 0.1 < 0.1 < 0.1 < 0.1 cis-12-dichloroethene < 0.1 < 0.1 < 0.1 < 0.1 bromochloromethane < 0.1 < 0.1 < 0.1 < 0.1 chloroform < 0.1 < 0.1 < 0.1 < 0.1 111-trichloroethane < 0.1 < 0.1 < 0.1 < 0.1 carbon tetrachloride < 0.1 < 0.1 < 0.1 < 0.1 1,1-dichloropropene < 0.1 < 0.1 < 0.1 < 0.1 benzene < 0.1 < 0.1 < 0.1 < 0.1 12-dichlorethane < 0.1 < 0.1 < 0.1 < 0.1 trichloroethylene < 0.1 < 0.1 < 0.1 < 0.1 12-dichloropropane < 0.1 < 0.1 < 0.1 < 0.1 dibromomethane < 0.1 < 0.1 < 0.1 < 0.1 bromodichloromethane < 0.1 < 0.1 < 0.1 < 0.1 trans-13-dichloropropene < 0.1 < 0.1 < 0.1 < 0.1 toluene < 0.1 < 0.1 < 0.1 < 0.1 cis-13-dichloropropene < 0.1 < 0.1 < 0.1 < 0.1 112-trichloroethane < 0.1 < 0.1 < 0.1 < 0.1 tetrachloroethylene < 0.1 < 0.1 < 0.1 < 0.1 13-dichloropropane < 0.1 < 0.1 < 0.1 < 0.1 dibromochloromethane < 0.1 < 0.1 < 0.1 < 0.1


WindrowControl

Garden waste

and chip

Tunnel control

Tunnel chip

12-dibromoethane < 0.1 < 0.1 < 0.1 < 0.1 chlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 1112-tetrachloroethane < 0.1 < 0.1 < 0.1 < 0.1 ethylbenzene < 0.1 < 0.1 < 0.1 < 0.1 mp-xylene < 0.1 < 0.1 < 0.1 < 0.1 o-xylene < 0.1 < 0.1 < 0.1 < 0.1 styrene < 0.1 < 0.1 < 0.1 < 0.1 bromoform < 0.1 < 0.1 < 0.1 < 0.1 isosproylbenzene < 0.1 < 0.1 < 0.1 < 0.1 bromobenzene < 0.1 < 0.1 < 0.1 < 0.1 123-trichloropropane < 0.1 < 0.1 < 0.1 < 0.1 1122-tetrachloroethane < 0.1 < 0.1 < 0.1 < 0.1 n-propylbenzene < 0.1 < 0.1 < 0.1 < 0.1 2-chlorotoluene < 0.1 < 0.1 < 0.1 < 0.1 4-chlorotoluene < 0.1 < 0.1 < 0.1 < 0.1 135-trimethylbenzene < 0.1 < 0.1 < 0.1 < 0.1 tert-butylbenzene < 0.1 < 0.1 < 0.1 < 0.1 sec-butylbenzene < 0.1 < 0.1 < 0.1 < 0.1 13-dichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 p-isopropyltoluene < 0.1 < 0.1 < 0.1 < 0.1 12-dichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 n-butylbenzene < 0.1 < 0.1 < 0.1 < 0.1 12-dibromo3chloropropane < 0.1 < 0.1 < 0.1 < 0.1 135-trichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 124-trichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 123-trichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 124-trimethylbenzene < 0.1 < 0.1 < 0.1 < 0.1 Hexachlorobutadiene < 0.1 < 0.1 < 0.1 < 0.1 Vinyl chloride < 0.1 < 0.1 < 0.1 < 0.1

SVOC ANALYSIS (mg/kg) Phenol < 1.0 < 1.0 < 1.0 < 1.0 2-picoline < 1.0 < 1.0 < 1.0 < 1.0 Analine < 1.0 < 1.0 < 1.0 < 1.0 o-toluidine < 1.0 < 1.0 < 1.0 < 1.0 bis(2-chloroethyl)ether < 1.0 < 1.0 < 1.0 < 1.0 2-chlorophenol < 1.0 < 1.0 < 1.0 < 1.0 1,3-dichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 Benzyl alcohol < 1.0 < 1.0 < 1.0 < 1.0 1,4-dichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 1,2-dichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 bis(2-chloroisopropyl)ether < 1.0 < 1.0 < 1.0 < 1.0 n-nitroso-di-n-propylamine < 1.0 < 1.0 < 1.0 < 1.0 Hexachloroethane < 1.0 < 1.0 < 1.0 < 1.0 2-methylphenol < 1.0 < 1.0 < 1.0 < 1.0 Nitrobenzene < 1.0 < 1.0 < 1.0 < 1.0 4-methylphenol < 1.0 < 1.0 < 1.0 < 1.0 Isophorone < 1.0 < 1.0 < 1.0 < 1.0 2,4-dimethylphenol < 1.0 < 1.0 < 1.0 < 1.0 Acetophenone < 1.0 < 1.0 < 1.0 < 1.0


WindrowControl

Garden waste

and chip

Tunnel control

Tunnel chip

2-nitrophenol < 1.0 < 1.0 < 1.0 < 1.0 bis(2-chloroethoxy)methane < 1.0 < 1.0 < 1.0 < 1.0 2,4-dichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 1,2,4-trichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 Hexachlorobutadiene < 1.0 < 1.0 < 1.0 < 1.0 4-chloro3-methylphenol < 1.0 < 1.0 < 1.0 < 1.0 2-methylnaphthalene < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosopiperidine < 1.0 < 1.0 < 1.0 < 1.0 2,4,6-trichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 2,4,5-trichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 2-chloronapthalene < 1.0 < 1.0 < 1.0 < 1.0 Dimethylphthalate < 1.0 < 1.0 < 1.0 < 1.0 2,6-dinitrotoluene < 1.0 < 1.0 < 1.0 < 1.0 2,4-dinitrotoluene < 1.0 < 1.0 < 1.0 < 1.0 Benzoic acid < 1.0 < 1.0 < 1.0 < 1.0 Diethylphthalate < 1.0 < 1.0 < 1.0 < 1.0 4-nitrophenol < 1.0 < 1.0 < 1.0 < 1.0 4-chlorophenyl-phenylether < 1.0 < 1.0 < 1.0 < 1.0 Carbozole < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosodiphenylamine < 1.0 < 1.0 < 1.0 < 1.0 4-bromophenyl-phenylether < 1.0 < 1.0 < 1.0 < 1.0 4-chloroaniline < 1.0 < 1.0 < 1.0 < 1.0 Hexachlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 Pentachlorophenol < 1.0 < 1.0 < 1.0 < 1.0 26-dichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 di-n-butylphthalate < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosodibutylamine < 1.0 < 1.0 < 1.0 < 1.0 Butylbenzylphthalate < 1.0 < 1.0 < 1.0 < 1.0 1245-tetrachlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 bis(2-ethylhexyl)phthalate < 1.0 < 1.0 < 1.0 < 1.0 di-n-octylphthalate < 1.0 < 1.0 < 1.0 < 1.0 Hexachlorocyclopentadien < 1.0 < 1.0 < 1.0 < 1.0 2-nitroaniline < 1.0 < 1.0 < 1.0 < 1.0 3-nitroaniline < 1.0 < 1.0 < 1.0 < 1.0 Dibenzoform < 1.0 < 1.0 < 1.0 < 1.0 Pentachlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 12-diphenylhydrazine < 1.0 < 1.0 < 1.0 < 1.0 2-naphthylamine < 1.0 < 1.0 < 1.0 < 1.0 2346-tetrachlorophenol < 1.0 < 1.0 < 1.0 < 1.0 4-nitroaniline < 1.0 < 1.0 < 1.0 < 1.0 2-methyl-46-dinitrophenol < 1.0 < 1.0 < 1.0 < 1.0 Diphenylamine < 1.0 < 1.0 < 1.0 < 1.0 Phenacetin < 1.0 < 1.0 < 1.0 < 1.0 4-aminobiphenyl < 1.0 < 1.0 < 1.0 < 1.0 Benzidine < 1.0 < 1.0 < 1.0 < 1.0 Dimethylaminoazobenzene < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosodimethylamine < 1.0 < 1.0 < 1.0 < 1.0 33-dichlorobenzidine < 1.0 < 1.0 < 1.0 < 1.0 7,12-dimethylbenz(a)anth < 1.0 < 1.0 < 1.0 < 1.0


WindrowControl

Garden waste

and chip

Tunnel control

Tunnel chip

3-methylcholanthrene < 1.0 < 1.0 < 1.0 < 1.0

PCB CONGENERS (mg/kg) PCB 28 < 0.01 < 0.01 < 0.01 < 0.01 PCB 52 < 0.01 < 0.01 < 0.01 < 0.01 PCB 101 < 0.01 < 0.01 < 0.01 < 0.01 PCB 118 < 0.01 < 0.01 < 0.01 < 0.01 PCB 153 < 0.01 < 0.01 < 0.01 < 0.01 PCB 138 < 0.01 < 0.01 < 0.01 < 0.01 PCB 180 < 0.01 < 0.01 < 0.01 < 0.01

PHENOLS (mg/kg) Catechol < 0.1 < 0.1 <0.1 < 0.1 Phenol < 0.1 0.1 0.1 0.1 Cresols < 0.1 < 0.1 <0.1 < 0.1 Xylenols < 0.1 < 0.1 <0.1 < 0.1 Trimethylphenol < 0.1 < 0.1 <0.1 < 0.1 Total phenols < 0.5 < 0.5 < 0.5 < 0.5


Table 52 Non PAS 100 contaminants in the MDF trials WindrowControl

Windrow MDF

Tunnel MDF

Tunnel control

Total Fluoride (mg/kg) DM 85.0 55.0 62.0 59.0 Total Arsenic (mg/kg) DM 11.0 11.1 7.9 6.8 Naphthalene (mg/kg) Air Dried 2.5 0.5 1.9 4.1 Acenaphthylene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Acenaphtene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Fluorene (mg/kg) Air Dried 0.8 < 0.5 0.4 0.6 Phenanthrene (mg/kg) Air Dried < 0.5 0.4 0.7 Anthracene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Fluoranthene (mg/kg) Air Dried 1.1 0.8 1.0 1.0 Pyrene (mg/kg) Air Dried 1.0 < 0.5 0.4 0.7 Benzo(a)anthracene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Chrysene (mg/kg) Air Dried 0.6 < 0.5 0.4 <0.5 Benzo(b)fluoranthene (mg/kg) Air Dried 0.8 < 0.5 0.4 0.9 Benzo(k)fluoranthene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Benzo(a)pyrene (mg/kg) Air Dried <0.5 < 0.5 0.4 <0.5 Dibenzo(ah)anthracene (mg/kg) Air Dried < 0.5 < 0.5 0.4 <0.5 Benzo(g,h,I)perylene (mg/kg) Air Dried 0.9 < 0.5 0.8 0.8 Indeno(123-cd)pyrene (mg/kg) Air Dried <0.5 < 0.5 0.4 <0.5 Formaldehyde (mg/kg) 1.3 33.8 15.6 0.9 PAH Screen (mg/kg) 10.0 To follow To follow 10.5

VOC ANALYSIS (mg/kg) 11-dichloroethene < 0.1 < 0.1 < 0.1 < 0.1 Dichloromethane < 0.1 < 0.1 < 0.1 < 0.1 trans-12-dichlororethane < 0.1 < 0.1 < 0.1 < 0.1 2,2-dichloropropane < 0.1 < 0.1 < 0.1 < 0.1 cis-12-dichloroethene < 0.1 < 0.1 < 0.1 < 0.1 bromochloromethane < 0.1 < 0.1 < 0.1 < 0.1 chloroform < 0.1 < 0.1 < 0.1 < 0.1 111-trichloroethane < 0.1 < 0.1 < 0.1 < 0.1 carbon tetrachloride < 0.1 < 0.1 < 0.1 < 0.1 1,1-dichloropropene < 0.1 < 0.1 < 0.1 < 0.1 benzene < 0.1 < 0.1 < 0.1 < 0.1 12-dichlorethane < 0.1 < 0.1 < 0.1 < 0.1 trichloroethylene < 0.1 < 0.1 < 0.1 < 0.1 12-dichloropropane < 0.1 < 0.1 < 0.1 < 0.1 dibromomethane < 0.1 < 0.1 < 0.1 < 0.1 bromodichloromethane < 0.1 < 0.1 < 0.1 < 0.1 trans-13-dichloropropene < 0.1 < 0.1 < 0.1 < 0.1 toluene < 0.1 < 0.1 < 0.1 < 0.1 cis-13-dichloropropene < 0.1 < 0.1 < 0.1 < 0.1 112-trichloroethane < 0.1 < 0.1 < 0.1 < 0.1 tetrachloroethylene < 0.1 < 0.1 < 0.1 < 0.1 13-dichloropropane < 0.1 < 0.1 < 0.1 < 0.1 dibromochloromethane < 0.1 < 0.1 < 0.1 < 0.1 12-dibromoethane < 0.1 < 0.1 < 0.1 < 0.1 chlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 1112-tetrachloroethane < 0.1 < 0.1 < 0.1 < 0.1 ethylbenzene < 0.1 < 0.1 < 0.1 < 0.1 mp-xylene < 0.1 < 0.1 < 0.1 < 0.1


WindrowControl

Windrow MDF

Tunnel MDF

Tunnel control

o-xylene < 0.1 < 0.1 < 0.1 < 0.1 styrene < 0.1 < 0.1 < 0.1 < 0.1 bromoform < 0.1 < 0.1 < 0.1 < 0.1 isosproylbenzene < 0.1 < 0.1 < 0.1 < 0.1 bromobenzene < 0.1 < 0.1 < 0.1 < 0.1 123-trichloropropane < 0.1 < 0.1 < 0.1 < 0.1 1122-tetrachloroethane < 0.1 < 0.1 < 0.1 < 0.1 n-propylbenzene < 0.1 < 0.1 < 0.1 < 0.1 2-chlorotoluene < 0.1 < 0.1 < 0.1 < 0.1 4-chlorotoluene < 0.1 < 0.1 < 0.1 < 0.1 135-trimethylbenzene < 0.1 < 0.1 < 0.1 < 0.1 tert-butylbenzene < 0.1 < 0.1 < 0.1 < 0.1 sec-butylbenzene < 0.1 < 0.1 < 0.1 < 0.1 13-dichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 p-isopropyltoluene < 0.1 < 0.1 < 0.1 < 0.1 12-dichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 n-butylbenzene < 0.1 < 0.1 < 0.1 < 0.1 12-dibromo3chloropropane < 0.1 < 0.1 < 0.1 < 0.1 135-trichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 124-trichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 123-trichlorobenzene < 0.1 < 0.1 < 0.1 < 0.1 124-trimethylbenzene < 0.1 < 0.1 < 0.1 < 0.1 hexachlorobutadiene < 0.1 < 0.1 < 0.1 < 0.1 vinyl chloride < 0.1 < 0.1 < 0.1 < 0.1

SVOC ANALYSIS (mg/kg) phenol < 1.0 < 1.0 < 1.0 < 1.0 2-picoline < 1.0 < 1.0 < 1.0 < 1.0 analine < 1.0 < 1.0 < 1.0 < 1.0 o-toluidine < 1.0 < 1.0 < 1.0 < 1.0 bis(2-chloroethyl)ether < 1.0 < 1.0 < 1.0 < 1.0 2-chlorophenol < 1.0 < 1.0 < 1.0 < 1.0 1,3-dichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 benzyl alcohol < 1.0 < 1.0 < 1.0 < 1.0 1,4-dichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 1,2-dichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 bis(2-chloroisopropyl)ether < 1.0 < 1.0 < 1.0 < 1.0 n-nitroso-di-n-propylamine < 1.0 < 1.0 < 1.0 < 1.0 hexachloroethane < 1.0 < 1.0 < 1.0 < 1.0 2-methylphenol < 1.0 < 1.0 < 1.0 < 1.0 nitrobenzene < 1.0 < 1.0 < 1.0 < 1.0 4-methylphenol < 1.0 < 1.0 < 1.0 < 1.0 isophorone < 1.0 < 1.0 < 1.0 < 1.0 2,4-dimethylphenol < 1.0 < 1.0 < 1.0 < 1.0 acetophenone < 1.0 < 1.0 < 1.0 < 1.0 2-nitrophenol < 1.0 < 1.0 < 1.0 < 1.0 bis(2-chloroethoxy)methane < 1.0 < 1.0 < 1.0 < 1.0 2,4-dichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 1,2,4-trichlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 hexachlorobutadiene < 1.0 < 1.0 < 1.0 < 1.0


WindrowControl

Windrow MDF

Tunnel MDF

Tunnel control

4-chloro3-methylphenol < 1.0 < 1.0 < 1.0 < 1.0 2-methylnaphthalene < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosopiperidine < 1.0 < 1.0 < 1.0 < 1.0 2,4,6-trichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 2,4,5-trichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 2-chloronapthalene < 1.0 < 1.0 < 1.0 < 1.0 dimethylphthalate < 1.0 < 1.0 < 1.0 < 1.0 2,6-dinitrotoluene < 1.0 < 1.0 < 1.0 < 1.0 2,4-dinitrotoluene < 1.0 < 1.0 < 1.0 < 1.0 benzoic acid < 1.0 < 1.0 < 1.0 < 1.0 diethylphthalate < 1.0 < 1.0 < 1.0 < 1.0 4-nitrophenol < 1.0 < 1.0 < 1.0 < 1.0 4-chlorophenyl-phenylether < 1.0 < 1.0 < 1.0 < 1.0 carbozole < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosodiphenylamine < 1.0 < 1.0 < 1.0 < 1.0 4-bromophenyl-phenylether < 1.0 < 1.0 < 1.0 < 1.0 4-chloroaniline < 1.0 < 1.0 < 1.0 < 1.0 Hexachlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 Pentachlorophenol < 1.0 < 1.0 < 1.0 < 1.0 26-dichlorophenol < 1.0 < 1.0 < 1.0 < 1.0 di-n-butylphthalate < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosodibutylamine < 1.0 < 1.0 < 1.0 < 1.0 Butylbenzylphthalate < 1.0 < 1.0 < 1.0 < 1.0 1245-tetrachlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 bis(2-ethylhexyl)phthalate < 1.0 < 1.0 < 1.0 < 1.0 di-n-octylphthalate < 1.0 < 1.0 < 1.0 < 1.0 Hexachlorocyclopentadien < 1.0 < 1.0 < 1.0 < 1.0 2-nitroaniline < 1.0 < 1.0 < 1.0 < 1.0 3-nitroaniline < 1.0 < 1.0 < 1.0 < 1.0 Dibenzoform < 1.0 < 1.0 < 1.0 < 1.0 Pentachlorobenzene < 1.0 < 1.0 < 1.0 < 1.0 12-diphenylhydrazine < 1.0 < 1.0 < 1.0 < 1.0 2-naphthylamine < 1.0 < 1.0 < 1.0 < 1.0 2346-tetrachlorophenol < 1.0 < 1.0 < 1.0 < 1.0 4-nitroaniline < 1.0 < 1.0 < 1.0 < 1.0 2-methyl-46-dinitrophenol < 1.0 < 1.0 < 1.0 < 1.0 Diphenylamine < 1.0 < 1.0 < 1.0 < 1.0 Phenacetin < 1.0 < 1.0 < 1.0 < 1.0 4-aminobiphenyl < 1.0 < 1.0 < 1.0 < 1.0 Benzidine < 1.0 < 1.0 < 1.0 < 1.0 Dimethylaminoazobenzene < 1.0 < 1.0 < 1.0 < 1.0 n-nitrosodimethylamine < 1.0 < 1.0 < 1.0 < 1.0 33-dichlorobenzidine < 1.0 < 1.0 < 1.0 < 1.0 7,12-dimethylbenz(a)anth < 1.0 < 1.0 < 1.0 < 1.0 3-methylcholanthrene < 1.0 < 1.0 < 1.0 < 1.0

PCB CONGENERS (mg/kg) PCB 28 < 0.01 < 0.01 < 0.01 < 0.01 PCB 52 < 0.01 < 0.01 < 0.01 < 0.01 PCB 101 < 0.01 < 0.01 < 0.01 < 0.01


WindrowControl

Windrow MDF

Tunnel MDF

Tunnel control

PCB 118 < 0.01 < 0.01 < 0.01 < 0.01 PCB 153 < 0.01 < 0.01 < 0.01 < 0.01 PCB 138 < 0.01 < 0.01 < 0.01 < 0.01 PCB 180 < 0.01 < 0.01 < 0.01 < 0.01

PHENOLS (mg/kg) Catechol < 0.1 <0.1 <0.1 <0.1 Phenol < 0.1 0.3 0.4 0.1 Cresols < 0.1 0.2 <0.1 <0.1 Xylenols < 0.1 <0.1 <0.1 <0.1 Trimethylphenol < 0.1 <0.1 <0.1 <0.1 Total phenols < 0.5 0.4 0.4 < 0.5


REFERENCES

2Bromhead, A. (2003) Reducing Wood Waste in Furniture Manufacture. Fauna & Flora International, Cambridge, UK Riddoch, S, (1999) Wood Residues - Waste or Resource?, Trada 3 Beebe, E., and England, J. (1998) Lead concentrations in processed C&D 4 Lavendel, B. (1996) Recycled wood and plastic composites find markets.

5 Steuteville, R. (1997) Large scale wood processing and marketing. Biocycle 38: 50-53. 6 Richard, T.L., Municipal Solid Waste Composting: Physical Processing, Cornell University, http://compost.css.cornell.edu/MSWFactSheets/msw.fs1.html 7 WRAP (2004) Recycling wood waste: how furniture manufacturers can cut costs and boost profits, WRAP, Oxon., England 8 FIRA (2003) Composting of wood waste from the furniture industry: Waste to profit: The fertile demonstration project, FIRA International, Stevenage, England 9 Valzano, F., (2000) A literature review on the composting of composite wood products, The University of New South Wales, Sydney, Australia 10 Valzano,F., Jackson,F., (2000) Laboratory Test Results and Site Inspection Report from the Composite Wood Composting Trial, The University of New South Wales, Sydney, Australia 11 Anon, Timber composites (2002), Trada 12 Composting Association (2005) The state of composting in the UK, (2003/2004) Composting Association 13 Connecticut Department of Environmental Protection, Business Recycling Old Corrugated Cardboard, http://dep.state.ct.us/wst/recycle/corrugated.htm 14 Klein, H. (1995) Coating technology for the manufacture of printing paper and folding box cardboard, Coating (Switzerland). Vol. 28, no. 6, pp. 196-200 15 Droz, C. and Grob, K, (1997) Determination of food contamination by mineral oil material from printed cardboard using on-line coupled LC-GC-FIDFID, In: European Food Research and Technology, Springer-Verlag GmbH, 239 - 241 16 Kunjappu, J., (2003) Ink chemistry, http://www.chemsoc.org/chembytes/ezine/2003/kunjappu_mar03.htm, CH 17 The Composting Association (2001) State of composting in the UK 1999, The Composting Association 18 The Composting Association (2003) State of Composting in the UK 2001-02, The Composting Association 19 The Composting Association (2004) The State of Composting in the UK 2003-04, The Composting Association 20 The Composting Association (2006). The State of Composting in the UK 2005-05, The Composting Association 21 EU (1999) Council Directive on Landfill of Waste ( 99/31/EC) Official Journal of the European Communities L 182/1, 16/7/1999


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