Issue 2 • October 2004

• Household Waste Management Options for dealing with our Rubbish

• Advantages and Disadvantages of the Waste Management Options

• Landfill• Thermal Treatments

• Mass Burn• Gasification• Pyrolysis

• Biodegradable Treatments• In-Vessel Composting

• Anaerobic Digestion

• Mechanical Treatments• Mechanical Biological Treatment

• Summary of the Options• Key issues from the Community Involvement Groups

• Next Steps

Introducing the Materials Resource Management Contract

Exploring the technologies availableto deal with our rubbish

No single waste management option, even waste reduction and recycling, is more effective than anyothers for dealing with all rubbish on grounds of environmental impact, cost and social acceptability. Every option has advantages and disadvantages, some more significant than others, andsome are made more or less important depending upon the characteristics of the local area andthe nature of the waste.

The summary outlined in this newsletter explores some advantages and disadvantages of each ofthe options discussed at the meetings of the Community Involvement Groups. The costs quotedfor each technology are dependant upon the size of the plant.

Household Waste Management Options forDealing with our Rubbish

Landfill is the controlled and engineered deposit of waste to land. In a landfill the rubbish degrades andstabilises over a long period of time.The engineering is required to control the emissions of landfill gas andleachate.

Leachate is produced when liquid in the rubbish is compressed out, and when rain falling on the site runsthrough the top of the landfill into the rubbish. Also, any water entering the site from surface streams mayadd to the leachate.

Leachate can be hazardous by virtue of the chemicals within it (including dissolved organic chemicals,ammonia and metals) which may contaminate land and water. However the leachate is extracted andtreated in a plant similar to a sewage works.

The rubbish we bury in the ground contains significant portions of organic materials that produce a variety of gaseous products that includes methane and carbon dioxide. The carbon dioxide that is producedis likely to disperse either into the air or it is soluble in water. Methane, on the other hand, which is lesssoluble in water and is lighter than air is likely to migrate out of the site. However, landfill gas energy plantscapture a very high proportion of the methane and it can be combusted for energy.

Often old mineral workings and extraction sites are used as landfills, providing a means to restore land.

Cost: £15 - £30 per tonne (but increasing due to Landfill Tax)

Landfill

Advantages and Disavantages of the WasteManagement Options

✓ Considerable operational experience inthe UK

✓ Improving technology and operation

✓ Potential to recover energy from largersites

✓ Has been traditionally low cost

✓ Low investment requirements in the short-term

✓ Can be used to restore mineral workings

✗ Limited space left in West Sussex✗ Costs are increasing and are expected to

equal other treatment options in thefuture

✗ Significant long-term enviromentalliabilities with after care of the sites

✗ Statutory targets are imposed to divertrubbish away from landfill

✗ Potential for leachate, odour and litterproblems

✗ Landfill is no longer considered asustainable option

✗ There are global impacts from methanegas

✗ There is substantial risk for latestoperators

AD

VA

NTA

GES

DIS

AD

VA

NTA

GES

Energy from Waste is the burning of waste under controlled conditions in which heat released isrecovered for a beneficial purpose. This may be to provide steam or hot water for industrial ordomestic uses, or for electricity generation.

There are essentially three types of thermal treatment:

1. Mass Burn

The most widely used Energy from Waste process is called“mass burn”. Waste is burned on a moving grate in aboiler with little or no pre-processing. Air is introducedbeneath and above the grate in carefully controlledamounts to ensure proper combustion.

Cost: Ranges from £35 - £50 per tonne (actual UKprocess)

2. Gasification

The waste is heated in a low oxygen atmosphereto generate a low heat content gas for burning in an

engine turbine or for combustion and heat recovery.

Thermal Treatments (Energy from Waste)

Chineham, Hampshire – Mass Burn Incinerator

Gasification Plant

✓ Deals with a large proportion of rubbish

✓ Reduces the volume of the rubbish

✓ Proven and commercially viable

✓ Recovers some ferrous metals

✓ Bottom ash can be recycled

✓ Provides maximum diversion away fromlandfill of biodegradable waste

✓ Generates energy

✓ Relatively low land use required

✗ Public concern over emissions andpotential health effects

✗ Can be difficult to site and obtainplanning permission

✗ Fly ash residue requires landfill disposal

✗ Poor history of older plant

✗ There is little available data forGasification and Pyrolysis plants

ADVANTAGES DISADVANTAGES

3. Pyrolysis

The waste is heated to high temperatures in theabsence of oxygen to produce a secondary fuelproduct, in the form of an oil or gas.

Cost: Gasification and Pyrolysis facilities costin the range of £50 - £65 per tonne (estimatefrom non UK source)

Pyrolysis Plant – Switzerland

Biological Treatments

In-Vessel Composting

Composting is a biological process in which micro-organisms convert degradable organic matterinto carbon dioxide and water vapour, using oxygen in the air, and leaving a residue which can beused as a compost.

The majority of composting schemes use the turned windrow method.A windrow is a process inwhich piles of shredded and mixed waste approximately 3 metres high, 4 metres wide and anylength, are constructed.The windrows are turned regularly to ensure an even mixture, to provideaeration and to control temperature and moisture.

Composting can be carried out in an enclosed building to reduce emissions and odours to improvethe process.Also, composting can be carried out in a sealed container to maximise the control ofthe composting process and any emissions.This is referrred to as In-vessel composting

Enclosed composting Site in France

✓ Generates potentially useful methane anda soil conditioner

✓ Contained plant, therefore environmentalproblems are reduced eg. odour andleachate

✓ Achieves a volume reduction in therubbish

✓ Reduces pollution problems if residue islandfilled

✓ Potential for additional recycling in thesorting process

✗ When used on mixed household wastecan present operational problems ifcontaminated with glass and plastics

✗ Only treats the organic part of the waste

✗ Marketing of final product can be difficult

✗ Relatively little experience in the UK

✗ Large area may be required forcomposting of the digestate

ADVANTAGES DISADVANTAGES

Anaerobic Digestion (AD)

Like composting, Anaerobic Digestion reduces the bulk of the organicwaste by converting it into a relatively stable residue.With AD,this is called a “digestate” which is similar to compost.Unlike composting, however, Anaerobic Digestionrequires an oxygen-free environment for the spe-cialised bacteria to function. The process pro-duces a flammable gas consisting mostly ofmethane and carbon dioxide.

Cost: Biological treatments cost from £35 - £70per tonne for clean, sorted waste. These costscan increase if the process has to sort and cleanmixed waste inputs. (estimate from non UK source)

Anaerobic Digestion site in Germany

Mechanical Biological Treatment is a mixture of some of the above processes,including elements of biological treatment with sorting and some refuse derived fuelproduction. This approach first sorts the waste to remove recyclable materials and wet putrescible materials (the element of the waste that willdegrade). The combustible residue is then shredded and burnt directly or trans-ported for fuel. Historically, the process involved compressing the fuel into refusederived fuel pellets.

The diagram below outlines the process of Mechanical Biological Treatment:-

Mechanical Treatment

✓ Reduces the volume of the waste

✓ Provides additional recycling

✓ More likely to get planning permission asthe different elements can be separated

✓ Efficient process as the feedstock to eachof the different processes are sorted

✓ Options to link to power generators

✗ Not well developed in UK

✗ Depends on all the processes functioningeffectively to be successful

✗ Emissions from the Refuse Derived Fuelplant are similar to other thermalprocesses

✗ Biological processes may have odour andbioaeresols emissions

✗ Sorting the waste may generate odoursand particulates

✗ Recyclables are low quality and thereforemarkets are not secure

✗ This is not a complete solution as itrequires thermal, biotreament and landfilltreatments

ADVANTAGES DISADVANTAGES

Cost: £45- £60 per tonne (actual UK process)

Residual

Waste

Pre-

processing

Biological

Fraction

Secondary

Materials

Recovered

Fuels

Anaerobic

Digestion

Glass, Metals etc

Co-Combustion

MSW Materials EnergyMechanical Biological Treatment

Glossary:ACT – Advanced Combustion Technology e.g. Gasification and Pyrolysis

IVC – In-Vessel Composting

AD – Anaerobic Digestion

MBT – Mechanical Biological Treatment

BMT – Biological Mechanical Treatment

RDF – Refuse Derived Fuel

MSW – Municipal Solid Waste

Medium to largeLargeLowLand use

Variable, improved

spread of risks

VariableGoodMarket

security

Compost, RDFCompost

Compost, biogas

Electricity

Electricity, gases, liquid

Products

MBT limited data

BMT limited data

IVC Med limited data

AD Med limited data

Mass burn Understood

ACT similar to EfW

Environmental

impacts

MBT limited

BMT limited

IVC Medium

AD Medium

Mass burn Good

ACT Limited

Cost

MBT limited

BMT limited

IVC Medium

AD Medium

Mass burn Good

ACT Limited

State of

development

Mechanical SystemBiological SystemThermal SystemIssue

Mechanical Biological Treatment Plant - Leicester

Summary of all the Options

Health and Safety – concerns surrounding toxins andpollutants, emissions and impact on local people aswell as those working in the plant. Short-termrisks were highlighted as a concern as well asany potential long-term risks.

Location and Landscape – there was concern thatthere is limited space left for the siting of wastefacilities in West Sussex. It was felt that there is anopportunity for discreet designs to be explored andovercoming the negative perception of waste facilities.

Transport and Infrastructure – There was concern that the local road infrastructure maynot be able to cope with the increased demand for the transportation of waste.

Costs and Economics – the Groups felt that they needed tounderstand the costs end economics of the options betterincluding the potential impacts on the Council Tax. It wasrecognised that any new plants may offer employmentopportunities in the area.

Facts and Figures – the groups felt that they wouldbenefit from more research which would providecomparison between the technologies, including moredata on the emissions.

Key Issues From the CommunityInvolvement Groups

The Community Involvement Groups will be meeting again to develop the criteria that willcontribute to the decision-making process through the “Democs” game. This is a policy-making tooldeveloped and implemented by the New Economics Foundation.

The Next Steps

“Could you please pass this newsletter on for someone

else to read - our goal is to get this information out

to as many residents in West Sussex as possible.”

Markets and Products – there was concern that some of the technologies were verydependant upon the provision of stable markets for the by-products.

Planning Priorities – there were some issues surrounding the impact that Government andRegional Strategies may have on the plans for West Sussex.

Communications, Consultation and Education – clear and targeted communications wereseen as crucial in order to deliver stakeholder engagement in the waste issues, includingaccepting responsibility for our own waste

Priorities, Power and Influence – the ability to trust thedecision makers was seen as a key issue and alsotrusting the engineers and scientists that will bedelivering the selected technologies. Delivering atransparent decision-making process wasimportant.

If you require further details about any of theinformation in this newsletter or if you wouldlike to receive any future issues then please

contact the Project Manager on (01243) 753570or email at: mrmc@westsussex.gov.uk

For further information:

Materials Resource Management ContractWastes Management Services

County Hall, Chichester,West Sussex. PO19 1RE

www.westsussex.gov.uk

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