management options for mixed waste organic outputs
TRANSCRIPT
MANAGEMENT OPTIONS FOR MIXED WASTE ORGANIC OUTPUTS Final Report
19 JULY 2021
Copyright © 2015 Arcadis. All rights reserved. arcadis.com
CONTACT
GAVIN HULL Senior Consultant, Waste
Advisory
T 02 8907 8377
M 0481 165 122
Arcadis
Level 16, 580 George Street,
Sydney, NSW, 2000
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NAMBUCCA VALLEY COUNCIL AND BELLINGEN SHIRE COUNCIL
MANAGEMENT OPTIONS FOR MIXED WASTE ORGANIC OUTPUTS
Draft Report
Author Frank Klostermann
Checker Gavin Hull
Approver Richard Collins
Report No Report Number
Date 19/07/2021
Revision Text 02
This report has been prepared for Nambucca Valley Council and Bellingen Shire
Council in accordance with the terms and conditions of appointment for Waste
Strategy for Nambucca and Bellingen dated 07/04/21. Arcadis Australia Pacific Pty
Limited (ABN 76 104 485 289) cannot accept any responsibility for any use of or
reliance on the contents of this report by any third party.
REVISIONS
Revision Date Description Prepared by Approved by
Rev01 12/05/2021 Draft report for comment FK, GH RC
Rev02 19/07/2021 Final report including NVC feedback FK, GH RC
V
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CONTENTS EXECUTIVE SUMMARY ............................................................................................................. 1
1 INTRODUCTION ....................................................................................................................... 3
1.1 Purpose ................................................................................................................................. 3
1.2 Scope of works ..................................................................................................................... 3
2 REVIEW OF POTENTIAL MWOO USE ................................................................................... 4
2.1 Background of MSW composting and MWOO use ........................................................... 4
2.2 Key differences between Australian jurisdictions ............................................................ 4
2.3 Primary disposal or recovery pathways for MWOO .......................................................... 5
2.4 Benefits and impacts of initial composting of mixed waste ............................................. 6
2.5 Review of the use of MWOO in a landfill context .............................................................. 7
2.6 Review of research on greenhouse benefits of MWOO .................................................... 9
2.7 Relative cost benefits of the use of MWOO ..................................................................... 10
3 DISCUSSION OF KEY FINDINGS ......................................................................................... 15
APPENDICES REFERENCES
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Management options for mixed waste organics outputs
EXECUTIVE SUMMARY
Mechanical biological treatment (MBT), also known as “Alternative Waste Treatment” in
Australia, of Municipal Solid Waste (MSW) is a mature process in Australia and
internationally, with an extensive inventory of facilities around the globe.
However, the business model for MBT processing of MSW is no longer viable in NSW
following regulatory reforms in 2018 that revoked permission to land apply the composted
mixed waste organic outputs (MWOO). With no other currently approved beneficial reuse
pathway, MWOO is being disposed of to landfill, which significantly reduces the promised
landfill diversion rate and increases costs.
The cost increase is exacerbated for the Biomass Solutions facility at Coffs Harbour by the
ending of the waste levy exemption on MWOO in May 2020. While the other three MBT
operators in NSW received a 12-month extension to the exemption until May 2022, this
was not offered to Biomass Solutions because the EPA believes it has “not demonstrated
sufficient progress or intent to transition to more sustainable resource recovery
outcomes”1. That has immediately added $84.10 per tonne in levy-related costs.
This has created an imperative to identify and implement an alternative pathway for
MWOO. MBT processing of mixed waste offers multiple potential benefits across both the
organic and residual fractions, which can be summarised as follows:
• Use of MWOO for its biofilter properties in various applications, including interim and
daily covers in existing landfills and phytocapping2 on landfills to be capped or closed
• Reduced greenhouse gas generation compared to landfilling unprocessed mixed waste (even where food and garden organics (FOGO) are separately collected)
• Stabilisation of organics in mixed waste, at minimum, allows MWOO and residual
waste to be disposed as a non-putrescible waste at potentially reduced gate fee
• Recovery of dry materials for recycling that would otherwise be lost to landfill or one-off energy recovery, therefore contributing to the higher order outcomes of
the waste hierarchy
• Use of MWOO in a landfill context can lead to significant cost savings for landfills,
which otherwise would have to import or stockpile large quantities of cover or capping
materials
• Use of MWOO as a precursor for production of refuse derived fuel (RDF), which has
to a large degree replaced fossil fuels in the European cement industry and provides
a landfill avoidance pathway for materials that are otherwise not recoverable.
The beneficial use of MWOO as a landfill biofilter is a key focus of this report, as it is the
primary short-term solution. Preliminary analysis indicates Nambucca Landfill may be able
to use as a minimum 2,900 tonnes of MWOO for cover purposes and one-off demand of
2,900 tonnes in final capping, subject to EPA approval. Further clarity is required on the
cost breakdown for cover and capping at Raleigh Landfill in Bellingen.
There are a range of key factors supporting this solution. It aligns with the NSW
Government’s own guidance indicating biofiltration systems can help improve the condition
of existing and even closed landfills3. The stabilisation benefits would also help meet
1 www.epa.nsw.gov.au/news/media-releases/2021/epamedia210503-waste-levy-exemption-extended-for-waste-facilities-
transitioning-to-organics 2 Phytocaps are an alternative to compacted clay capping for closed landfills, based on the principle of providing sufficient and
appropriate soil cover to grow plants that help evaporate stormwater in order to avoid ingress into the waste body underneath, while at the same time helping to oxidise methane emanating from landfill gas. For more detail on phytocaps, please refer to WMAA factsheets 1 – 3 (see Appendix) 3 Handbook for the design, construction, operation, monitoring and maintenance of a passive landfill gas drainage and
biofiltration system; the NSW Department of Environment, Climate Change and Water (now Department of Planning, Industry and Environment)
Priority 1 in the Net Zero Plan4 announced by the NSW Government in December 2020,
which aims to drive uptake of proven emissions reduction technologies and supports the
specific action to transition to net zero emissions from organic waste by 2030.
Finally, it is noted that organics typically continue to represent up to 30% of the
composition of mixed waste in a FOGO system, given average food organics capture rates
in NSW of 41% and garden organics capture rates of 98%5. In the absence of an MBT
facility this will go direct to landfill, generating greenhouse gases and losing the biofilter
benefits of MWOO in landfill cover applications.
4 Net Zero Plan Stage 1: 2020–2030, 2020, DPIE 5 Analysis of NSW Kerbside Green Lid Bin Audit Data Report, 2020, Rawtec for DPIE
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Management options for mixed waste organics outputs
1 INTRODUCTION
1.1 Purpose
In October 2018, the NSW EPA moved to end the land application of MWOO from
MBT facilities by revoking the general and specific Resource Recovery Orders and
Resource Recovery Exemptions (RRO/E) that permitted it.
This has fundamentally impacted the business model for Biomass Solutions’ (BIO)
England Road facility in Coffs Harbour, respectively that of the contracted council(s),
whereby the stabilised organic fraction is now disposed to landfill after treatment,
rather than applied to land at low or no cost.
Both Nambucca Valley Council (NVC) and Bellingen Shire Council (BSC) supply their
MSW mixed waste to BIO via a contract with Coffs Harbour City Council (CHCC). This
contract expires in 2027. NVC and BSC have asked Arcadis to explore potential uses
for the MWOO in order to avoid landfilling and reduce cost burden. Currently the
MWOO from BIO is disposed to landfill at Tamworth, NSW.
This project will seek to investigate the immediate options for the use and management of
MWOO, including recyclable recovery, contaminant removal and composting for managing
the organic fraction of mixed waste, in the current regulatory context. It aims to develop
the evidence base about the range of potential benefits from the MBT process, and to
quantify them to the extent possible.
Arcadis understand this document may be relied upon for communications with
government (local, state and federal), government agencies and other stakeholders,
including industry partners.
1.2 Scope of works
NVC and BSC commissioned Arcadis to undertake the following scope of works:
• Investigate immediate options for the management, including use, of MWOO produced at the Coffs Harbour Englands Road facility of Biomass Solutions (BIO), and assess relative benefits of each option for NVC and BSC.
• To agree with NVC and BSC on the preferred option(s) and support both councils in
negotiations with the EPA through written and verbal representations in order to
achieve the best outcome and most cost-effective use of MWOO, including (if
necessary) the conditions for a site specific Resource Recovery Order and Exemption
(RRO/E).
2 REVIEW OF POTENTIAL MWOO USE
Arcadis has undertaken a high-level desktop review of scientific and industry
literature regarding practices in the composting of MSW and resultant use of MWOO.
A refence list has been provided in Appendix A.
2.1 Background of MSW composting and MWOO use
According to the Environment Agency of England and Wales6, composting of MSW
organics started in the Netherlands in the 1930s but really took off in Europe in the 1970s
and 1980s due to the European Union landfill directive requiring all waste be treated
before landfilling. One of the main underlying drivers for treatment is to separate the
biodegradable fraction (i.e. organics) in MSW that causes greenhouse gas (GHG), odour
and leachate issues in landfills2.
Composting of MSW is typically conducted in mechanical biological treatment (MBT)
facilities, which is a generic term for a variety of plants that mechanically process (receive,
separate, recycle) and biologically treat MSW into various products, including a treated
(stabilised) organic fraction. It is called compost-like output (CLO) in Europe, and in NSW
is called MWOO (used henceforth).
MWOO is treated differently across EU member states, underpinned by the different
national drivers and regulations. For example, in Germany MWOO is sent to landfill as a
stabilised (pre-treated) product, in Greece it typically forms part of an RDF with a lower
calorific value (CV)4, while France, Italy and Spain, which have large MBT capacity for
processing MSW, sometimes apply outputs to land.
2.2 Key differences between Australian jurisdictions
While the NSW regulatory change is consistent with global trends, particularly across
Europe, it is not aligned with current policy positions in other Australian jurisdictions.
Most states have not implemented their own mandatory standards in relation to the
quality of composts but instead reference the AS4454 standard (Australian Standard
for Composts, soil conditioners and mulches), which is focused on processes and
product quality specifications.
NSW has five (5) MBTs, Queensland has one (in Cairns), Western Australia has two
in Perth (Canning Vale and Neerabup) and a de facto MBT in South Australia
combining mechanical sorting at Wingfield and MWOO maturation at the Northern
Balefill landfill at Dublin.
In NSW, regulation of organic outputs was initially via a specific Resource Recovery
Order/Exemption (RRO/E) that allowed the application of MWOO to land under certain
conditions and specifications. This RRO/E was revoked in late 2018.
In Queensland, MWOO from the Cairns Bedminster plant is applied to land typically used
for sugar cane plantations, which continues to date according to Arcadis’ knowledge.
In WA, the licences for the two MBTs do not contain any specific quality parameters for the
MWOO produced7. The MWOO produced by the Canning Vale plant, owned by the SMRC
regional government group, is transported 125 km to a separate processor, Nutrarich, in
Brookton, where the MWOO is blended with other soil conditioners as required and then
considered suitable for unrestricted use in farms, parks and gardens. Anecdotally, the
blended product has had issues for non-agricultural use due to its plastic content. The
NSW EPA does not support mixing or blending various waste products to essentially
achieve compliance by dilution.
6 Stratton-Maycock, Merrington (2009) 7 Talis (2019)
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Management options for mixed waste organics outputs
The MWOO from the Neerabup facility in north Perth is taken to the local C-Wise
composting facility as Organic Soil Conditioner and AS4454 compliant product. According
to local consultant Talis, there were very limited breaches of the relevant standards and
the product undergoes a testing regime and complies with an acceptable compost
standard outlined in an agreement between the parties (not publicly available).
Arcadis is also aware of one landfill in SA that has preliminary approval to use the fines
(organic fraction) of a very coarse MSW sorting process in a phytocap application to
landfill. It is yet to be seen the extent to which this preliminary approval will translate into a
larger scale use of these organic fines in the phytocap. Phytocaps are an alternative to
compacted clay capping for closed landfills, based on the principle of providing sufficient
and appropriate soil cover to grow plants that help evaporate stormwater to avoid ingress
into the waste body underneath whilst at the same time helping to oxidise methane
emanating from landfill gas.8
2.3 Primary disposal or recovery pathways for MWOO
As an overview, there are several pathways for disposal or recovery of MWOO, most of
which can be summarised under three main pathways, addressed in the following
sections.
2.3.1 Landfill or landfill related uses
MWOO is typically a stabilised product, meaning it is biologically stable and therefore has
reduced emissions of GHG and leachate. In a landfill or landfill use context, it can be:
• Directly landfilled
• Used as daily or interim cover
• Used as part of a phytocap after closure or part-closure
• Used elsewhere on the landfill site as part of a land reclamation or site remediation
material, provided the future use of the site has no planning constraints on the use of
MWOO, respectively the site has a specific RRO/E for the use of MWOO.
MWOO can operate as a methane oxidisation tool in landfill daily cover, when properly
applied and managed (i.e. moisture content is important to manage)9. The A-CAP
(Australian Alternative Covers Assessment Program6) trials have also shown that
phytocaps on closed landfills can help oxidise landfill gas as it percolates through the
phytocap (see also Venkatraman for detailed results of the A-CAP trials10).
MWOO has potential to replace a portion of the conventional topsoil or higher quality
compost in a phytocap, notably the part of the phytocap closest to the waste body11.
2.3.2 Land application – rehabilitation
In other states such as QLD and WA, and in some southern European countries,
specific land application pathways are possible, such as mine site rehabilitation, land
reclamation, as well as the use of MWOO as a nutrient and carbon carrier for forestry
and some agricultural uses. This is no longer available in NSW given the 2018
regulatory reforms.
8 Australian Alternative Covers Assessment Programs (A-CAP), WMAA, www.wmaa.com.au/aacap/aacap.html 9 Tanthachoon et al 10 Venkatraman (2009) 11 Abichou et al (2016)
2.3.3 Refuse Derived Fuel (RDF)
The MBT process in Europe is often the precursor for RDF production, through
contamination removal and either preparation of a specified fuel from the residual
fraction or conversion of the MWOO into a dry, carbonaceous material suitable for
energy recovery.
The viability of energy recovery in NSW is highly mediated by the collection service from
which it is sourced. The NSW Energy from Waste (EfW) Policy Statement identifies the
EfW-eligible proportion of MSW mixed waste according to each council’s bin configuration.
NVC, BSC and CHCC all have FOGO collection services, which as a best practice model
permits all mixed waste from the red-lid bin to go to EfW, increasing viability of this option.
However, the current relatively low maturity end market in Australia, with tight
specifications for RDF and no experience accepting varying grades of fuel, reduces the
prospect of MWOO-derived RDF being accepted in the short-term.
The only established offtake in NSW, Boral’s Berrima cement kiln, has an approved
specification addressing 17 parameters that produces a high-quality fuel, including
around moisture, chlorine, ash and calorific value12. This tight specification effectively
precludes use of MWOO in RDF.
While varying grades of RDF may emerge in time as the market matures and regulatory
environment evolves, it is not anticipated that RDF will provide an option for MWOO in
the short-term.
2.4 Benefits and impacts of initial composting of mixed waste
The main impacts of stabilised MWOO via the Biomass Solutions MBT process are outlined below.
2.4.1 Reduction in GHG emissions
The “B” in MBT stands for the biological part of the process and is typically a composting
process. This composting process stabilises the organic fraction of MSW, which
significantly reduces the production of methane when it is disposed of to landfill. Given
methane has a global warming potential 25 times that of CO2 over 100 years13, biological
stabilisation of organic waste before disposal can reduce the approx. 1.6% of Australian
GHG emissions that come from landfill12, helping Australia to meet its national climate
change target to reduce GHG emissions to 26- 38% below 2005 levels by 2030.
Stabilising the organic fraction of MSW results in a reduction of biodegradability, which
according to Ball et al, can deliver a reduction of around 50% of the GHG emissions of
MSW14. It should be noted that the exact reduction in GHG emissions is dependent on
factors such as stream composition, maturity of the organic fraction after treatment and
landfill gas capture rates. Therefore, results will vary on a case by case basis.
2.4.2 Mass loss
A further impact of the composting process is mass (and volume) reduction, mainly
through moisture loss (H2O), but also loss of CO2. Mass reduction of a complete
composting process alone would be around 30-35%, compared to the much longer period
required for mass reduction if disposed direct to landfill. As a result, there will be an
increase in the life expectancy of existing landfills compared to landfilling unprocessed
12 https://majorprojects.accelo.com/public/49b205e724f9ceb03fbe1877a39df51a/App%20B_%20Boral%20Berrima%20Solid%20
Waste%20Derived%20%20Fuel%20Specification_%20v1.pdf 13 Australia’s National Greenhouse Accounts, 2019, Department of Environment and Energy 14 Ball et al
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Management options for mixed waste organics outputs
MSW. Landfill life expectancy will be further increased via the recycling process, removing
of metals, plastics, glass and inert materials.
2.4.3 Leachate generation
Due to the abovementioned effects of mass loss and moisture loss when landfilling
stabilised organics rather than putrefying organics, a further impact of the composting of
mixed MSW is a reduction in the generation of leachate in landfill. Leachate management
is costly and one of the main environmental impacts of landfilling putrescible waste.
2.4.4 Classification as non-putrescible General Solid Waste
MWOO should be classified as a non-putrescible waste as a consequence of stabilisation during the composting phase of the MBT process. As a result, landfill gate fees should be less than putrescible waste. It can be disposed to any landfills solely licenced to accept non-putrescible waste, but such facilities are primarily in metropolitan areas, with landfills in regional areas invariably accepting all waste types.
2.4.5 Increased resource recovery
As outlined above, the MBT process separates inorganic from organic matter and then
recovers the various inorganic materials including recyclables (metals, plastics, glass
etc). Although a small volume, an estimated 3-5% of inputs can be captured for further
recycling.
The MBT process also provides benefits in the pre-processing of MSW to produce RDF
for an Energy from Waste (EfW) solution. It will remove contaminants, including heavy
metals and PVC plastics that are problematic in combustion, and increase efficiency to
provide an overall better outcome for the combustion process.
It should be noted that the Australian market for RDF is still in its infancy. Currently, in
accordance with NSW EPAs Energy from Waste Policy Statement, only a portion of MSW
could be used for an EfW solution (see also Table 1 of the current NSW EfW Policy
Statement. Any MSW destined for EfW currently has to go through a “processing” step
before the waste can be used for energy recovery purposes. It remains to be seen
whether the new 20 Year Waste Strategy and a potentially re-drafted EfW policy will
change any of these conditions.
2.5 Review of the use of MWOO in a landfill context
Mature MWOO displays the same properties as mature compost as far as landfill
biocovers or biofilter materials are concerned. Biocovers are hosts for methanotrophic
bacteria, which live in the moisture film (biofilm) around the organic matter and oxidise
methane (CH4) and volatile organic compounds (VOC) passing through the biocover. The
main difference to immature compost/MWOO is that the immature version is still
biologically degrading and thus exuding CO2, which interferes with development of the
biofilm.
Long term trials of a full-scale biocover at an active landfill have shown that landfill gas
(methane) can be oxidised by methanotrophic bacteria in landfill covers15. The bacteria
use the CH4 as their carbon and energy source, in turn producing CO2 and water. A mature
compost can oxidise methane of up to 100- 200g CH4/m2/day, whereas immature compost
can only oxidise 50-70g CH4/m2/day16.
A 4-year field trial at an Australian landfill showed the success of biofiltration of landfill gas
15 Pedersen (2010) 16 Yazdani, Imhoff
as a means of managing landfill gas emissions from low to moderate gas generation
landfill sites. The trial demonstrated maximum methane oxidation efficiencies greater than
90%, with average oxidation efficiencies greater than 50% over the 4 years of operation17.
This confirms other research showing that biocovers do not perform well under high
methane loads (500-700 g CH4/m2/day).
The thickness of the biocover also needs management and consideration, as thicker
covers tend to develop anaerobic pockets and retain the water generated by the CH4
oxidation process.
Compost biocovers can also significantly reduce odour emissions from landfills under
certain conditions, performing as a kind of biofilter. Trials have demonstrated that MWOO
is suitable for reducing odorous emissions from landfill surfaces, where the MWOO meets
density and moisture content specifications18. Results of the trials using landfill gas
showed a 69% odour reduction (Odour Units/m3) for MWOO with a bulk density of 590
kg/m3, and a reduction of 97% using MWOO with a bulk density of 740 kg/m3.
This could also open up an avenue for MWOO to be used as biofilter material in other
contexts, for example in tunnel composting facilities, whereby a biofilter functions as a
host for bacteria that consume (odour creating) volatile organic compounds passing
through the biofilter material18. The underlying principle here is the same as with the
biocover/biofilter application. The MWOO acts as a host for bacteria that consume the
volatile organic compounds that generate the offensive odour. Hence moisture
management, in order to maintain relevant biofilm, is important in this application.
As recognised in the Australian A-CAP trials, phytocaps applied at the closure of a landfill
or landfill cell help with the oxidisation of ongoing landfill gas, when designed and
managed appropriately8. They also minimise or eliminate the impacts of compromised
clay caps as landfills settle over a period of years. This unavoidable settlement can lead
to voids underneath the conventional clay cap, which can then crack or subside and allow
the ingress of stormwater leading to a compromised cap.
The concept of using a biofilter as a means to maximise oxidation of methane emissions
from landfills has also been widely recognised, with numerous designs for this purpose19.
The performance of such a biofilter will be affected by a number of parameters such as
temperature within the biofilter media, atmospheric pressure, landfill gas temperature,
moisture content of biofilter media, ambient temperature, methane load, etc. However, it
has been recognised that a biologically mature biofilter media will perform better than
immature ones19.
The above discussion demonstrates that stabilised MWOO is suitable for several
applications in a landfill context, such as (daily) biocover over an active landfill face, as an
interim layer for a part of the landfill that is not yet finished but also not being actively filled
or as part of a phytocap in the design of the final capping layer of the landfill.
Phytocaps are also cost effective. Lismore City Council was the first NSW council to
receive a licence for a phytocapped landfill. According to Lismore’s experience, the
phytocap cost half the amount spent on conventional capping for landfills.20 This
(anecdotal) cost benefit is particularly relevant if large amounts of capping material
(suitable clay) need to be imported, as they are not available on site. Also, a geosynthetic
clay liner as part of a landfill cap is relatively costly.
Finally, using MWOO in landfill applications addresses the main reasons the NSW EPA
revoked the application of MWOO to land, which was the scientific research that showed
physical and chemical contamination of the MWOO. This risk is addressed by using
MWOO in a landfill context, as either a daily or interim cover or as part of a final landfill
cap, as the MWOO would be “trapped” on a site that is licensed to provide safe, long-term
17 Dever, Swarbrick, Stuetz (2011) 18 Hurst et al (2005) 19 DECCW Handbook (2009) 20 https://northernriverswaste.com.au/our-phytocapping-site-a-nsw-first
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Management options for mixed waste organics outputs
waste disposal. From a regulatory perspective, the only practical difference to landfilling
MWOO and using it as a phytocap material would be that the material ends up
methodically placed in a layer on top of the landfill rather than inside it.
Allowing the beneficial use of MWOO in a landfill context as described above, rather than
demanding it be disposed to landfill, also has the following positive impacts:
• From a waste management and licencing point of view, it preserves airspace as the
MWOO can replace other daily, interim or final cover material
• From environmental and amenity perspectives, it reduces the pressure on finding and
developing new sites for landfilling
• From an economic point of view, it saves costs for many landfills that otherwise would
have to import materials for daily, interim or final covers.
2.6 Review of research on greenhouse benefits of MWOO
The impact of biostabilising MWOO is a significant reduction in biodegradability. Compared
to MSW, a mature MWOO is up to 50% less biodegradable12, which correlates to lower
GHG emissions and leachate production.
According to Ball et al, trials conducted for an AWT facility in Australia (unnamed) have
provided the following results in landfill gas production when comparing MSW, immature
compost and mature compost (Table 1).
It should be noted that MWOO is classified as immature or mature depending on how long
it has been subject to treatment. According to information obtained from BIO, its MWOO is
pasteurised but not yet mature. It would require an additional maturation process, typically
in an open windrow for 6-8 weeks. This process could be done on existing landfill sites,
subject to appropriate licensing. Once finished, MWOO would be used like a mature
compost.
Table 1: The landfill gas reduction benefits of stabilised MWOO
The reason for the difference in outcomes is that the available carbon in the organic fraction is mineralised during the biostabilisation process, becoming physically and biologically stable (more like a mineral) and leaving less available carbon for production of landfill gas.
It can be assumed that MWOO, when disposed of to landfill, will continue to biologically
degrade and produce GHG under anaerobic conditions (lacking oxygen) and therefore
convert to landfill gas (CH4), which is a potent GHG with 28 times global warming potential
(GWP). It can also be assumed that MWOO used as daily cover in a landfill will continue
to degrade biologically but not be subject to anaerobic conditions, and therefore mostly
generate CO2, having a much smaller GHG emission footprint.
Furthermore, MWOO used as daily cover will have the additional positive environmental
impact of odour suppression and methane oxidisation (Section 2.5). In total this should
be a strong argument for the use of MWOO as a daily cover rather than a material to be
Sample MSW Immature MWOO Mature MWOO
Total mean biogas production in litres per kg LOI (loss of ignition)
427.5
250.3
218.7
Standard error (+/-) 7.6 38.7 7.6
Biodegradability in % of feed 100% 58.5% 51.2%
disposed of to landfill directly, when directly comparing those two options.
2.7 Relative cost benefits of the use of MWOO
In the following, we will solely compare MWOO options in a landfill related context, given these are
the primary short-term opportunities in the region. The reason is that the other option, Refuse Derived
Fuel, is not immediately available or feasible for both NVC and BSC in an isolated assessment. It
could, however, play a role in a regional context in the longer term.
In order to assess the relative benefits of the use of MWOO as a landfill cover and capping material,
we need to start with the current cost structure of the landfills. This assessment is relative and
preliminary and will be amended once the full cost accounting for the landfills has been finalised (a
separate task within the overall project).
2.7.1 Nambucca
The currently active Nambucca landfill is located at 711 Old Coast Road, Nambucca Heads.
According to the site Landfill Environmental Management Plan (LEMP), the site has three stages with
a total airspace volume of approx. 1,220,000 m3 as per Table 2.
Table 2: Airspace capacity of Nambucca Landfill, by stage
Stage Area Airspace
Stage 1 3.8 ha 440,000 m3
Stage 2 2.5 ha 360,000 m3
Stage 3 2.6 ha 420,000 m3
Total 8.9 ha 1,220,000 m3
The current Stage 1 has 4 cells, of which cells 1 and 2 are filled and capped. Cell 3 is currently active.
Table 3 gives the area and airspace or all cells.
Table 3: Airspace capacity of stage 1, by cells
Cell Area Airspace
Cell 1 6,000 m2 60,000 m3
Cell 2 10,000 m2 90,000 m3
Cell 3 10,000 m2 120,000 m3
Cell 4 8,000 m2 120,000 m3
Total 34,000 m2 390,000 m3
Note that the airspace of stage 1 has reduced due to a water main that was not removed from the
landfill area. Each cell is double lined, with a HDPE and a GCL liner, which is best practice.
For NVC, the starting point is the current cost estimate for rehabilitation works for future landfill cells,
as established per the letter from Enginuity Design dated 28 June, 2019. According to this cost
estimate, the overall unit rate for any “top area” of any cell to be capped is $49/m2 and the unit rate for
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Management options for mixed waste organics outputs
any “sideslope area” to be capped is $32/m2. These rates include $20/m3 for winning of topsoil from
the Stage 2 area, including mixing, mulching and placing and seeding the topsoil.
The landfill site will eventually run out of cover and topsoil material to be won on site, which would
then mean the import of cover and topsoil material, resulting in a potentially significant increase in
costs to NVC. While this lack of cover material is currently only expected to occur in the far future (in
around 20 years’ time), this issue could be brought forward should NVC need to increase its landfill
intake due to any early expiry of the Biomass Solutions contract or negotiated outcome (and potential
early closure of the facility), including an acceptance of some MWOO or waste due to England Road
landfill being full.
According to Enginuity Design, the currently operating cell 3 of Stage 1 will require capping in 2024.
With some time required to negotiate EPA approval (Section 2.7.4) and to design and test a phytocap,
the timing may be convenient. The capping works for cell 3 will cover an area of 6,000 m2, which is for
the so called “Top Area” only as the “sideslope area” of cell 3 will be done incrementally as the cell
fills up and be covered under operational cost.
The estimated cost for conventional capping of cell 3 is $323,000 (excl. GST), including a 10%
contingency to cover any price increases for the period since 2019 when the cost estimate was done,
plus any uncertainties. This cost is reflective of $49/m2 x 6,000 m2, plus 10% contingency.
Included in the $49/m2 for capping the “Top Area” are $18/m2 for a seal layer and $18/m2 for a water
drainage layer. Neither layer would be required for a phytocap, so theoretically the remaining capping
cost unit rate for the “Top Area” should be closer to $13/m2. This would avoid $237,600 in
conventional costs for an engineered cap for capping cell 3 (i.e. 6,000 m2 x $36, plus 10%), a 70%
cost reduction.
Of the current conventional capping works and costs, the following would remain in place:
• Seal Bearing Layer – $1.50/m2
• Revegetation Layer for sub-soil growing medium - $9.50/m2
• Revegetation Layer for topsoil - 2.00/m2
• Total - $13/m2.
Estimating the cost of MWOO inputs for capping requires assumptions on input volumes and unit
costs. The NSW EPA landfill guide for phytocaps recommends an approximate depth of 1.5 m for a
phytocap (should it be approved), while a specific design report would specify the proportional blend
of MWOO and other soil materials to achieve the correct mix for individual landfills. Given the onsite
soils used at Nambucca, as well as the BSC landfills, are weathered phyllite that does not contain
organic matter, we have assumed at least 50% of the phytocap is MWOO in order to meet the EPA
guidelines that phytocaps should have soils with “moderate to high organic content”.
On the basis that each m2 would have 0.75 m depth of MWOO, a volume of 4,500m3 of MWOO might
be required for the 6,000 m2 cap of cell 3.
For consistency we assume the similar volumetric rates for capping as stipulated in the Enginuity
letter mentioned above. The phytocap would replace the revegetation layer, except for the topsoil
component. The volumetric rate for the 50/50 mix of site soils (weathered phyllite and MWOO) should
be less than the $20/m3 assumed by Enginuity as it does not require winning, transporting of site
soils, mulching, mixing of greenwaste, placement and spreading of the soil mix. For the phytocap,
only half the site will need to be won and transported and no mulching is required. We have assumed
a volumetric rate of $10/m3.
Table 4 provides the difference in layers and costs. It shows the total cost for a phytocap is estimated
to be $122,100 ($18.5 x 6,000m2 + 10%), versus the $323,000 cost of a conventional engineered cap.
This is a potential saving of $200,900, or 62%.
Table 4: High level cost comparison of a convention landfill cap and phtyocap.
Conventional Cap Phytocap
Seal bearing layer $1.5/m2 Seal bearing layer $1.5/m2
Seal Layer $18/m2 Sal layer nil
Water drainage layer $18/m2 Water drainage layer nil
Reveg layer sub-soil $9.5/m2 Phytocap subsoil $15/m2
Reveg layer topsoil $2/m2 Phytocap topsoil $2/m2
Total $49/m2 Total $18.5/m2
A further cost saving could be the use of MWOO as daily and interim cover material. The above letter
from Enginuity Design does not stipulate a cost for winning and placing daily and interim cover,
however, it can be assumed that the cost would be a fraction of the volumetric rate of $20/m3. We
assume a volumetric rate of $10/m3 when using MWOO, as stated above.
According to EPA landfill guidelines, daily cover should be at least 150mm and interim cover at least
300mm thick. The guidelines state that waste derived organic materials (i.e. MWOO) can be approved
for daily cover, whereas using MWOO or a mix of MWOO and VENM (site soil) as interim cover may
require a licence amendment. As cell 3 has an overall area of 10,000m2, we assume that, as a
minimum, 10,000m2 could be utilised for interim cover at a depth of 300mm, with daily cover to a
depth of 150mm used progressively across the full 10,000m2 cell area.
The combined depth of MWOO for daily and interim cover is therefore 0.45m. This equates to
4,500m3 of MWOO, as a minimum, that could be utilised for these purposes (i.e. 10,000m2 x 0.45m).
At a cost saving of $10/m3 compared to conventional materials, that is a potential reduction in the cost
of cover materials by $45,000. Obviously, as each lift of waste in a cell requires daily cover and
several areas may require interim covers, this amount of MWOO and the associated saving would
increase.
Therefore, Nambucca Landfill’s total minimum demand for MWOO is 4,500 m3 for cover purposes for
cell 3 and a further 4,500 m3 for final capping of cell 3. At an average density of 650kg/m3, this
equates to recurring demand of at least 2,900 tonnes of MWOO for covers and one-off demand of
2,900 tonnes in capping. Cell 4 would create additional demand, which can be assessed using the
above approach.
Finally, further cost savings could be achieved by “crystalising” some of the cost savings that would
be achieved by not sending the MWOO for disposal to Tamworth landfill, as is currently the case. The
current cost of transport plus disposal of MWOO to Tamworth is an “opportunity cost” to Coffs
Harbour City Council (CHCC), which it is seeking to pass on to NVC and BSC. Independent of any
dispute about transport costs, both NVC and BSC should be able to charge a fee for receiving and
handling the MWOO as long as it is below the transport cost to Tamworth, or other potential solution.
This would be a negotiated outcome between the councils involved.
The breakdown of the financial impact of being able to utilise MWOO is summarised in Table 5.
Table 5: Costs and savings of using MWOO in NVC landfill
Aspect Cost vs conventional
Savings of engineered final cover - $200,900
Minimum savings of using MWOO in daily and interim cover - $45,000
Savings Tamworth solution TBC
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Management options for mixed waste organics outputs
2.7.2 Bellingen
Bellingen has currently two active landfills. The landfill at Dorrigo (Old Coramba Road) is unlined and
has little airspace left, so is not further considered. The landfill at Raleigh (146 Short Cut Road) is also
unlined but active.
According to information obtained from BSC, the Raleigh Landfill uses 1,500m3 per annum for cover
and capping material at a cost of $31,000, which means capping material has a cost of $20.66/m3, an
amount nearly identical to the Nambucca landfill for winning, mixing and placing of topsoil.
Again, using the same assumption in regard to potential savings, Raleigh Landfill could cut its landfill
cover and capping cost by at least $10/m3, which is a $15,000 saving. In addition to that, BSC would
also be able to gain a benefit from charging for receiving MWOO or receiving an agreed portion of
saving the “opportunity cost” of transporting and disposing of the MWOO at Tamworth landfill.
Given that each landfill requires its own specific phytocap design, including trials, it is unlikely that the
Raleigh Landfill would obtain a net benefit from a phytocap, as the costs of obtaining approvals would
outweigh the potential cost benefit compared to a conventional cover and cap. In addition, from
experience, it may be very difficult to obtain a phytocap approval for an unlined landfill.
We have not taken into account the Dorrigo Landfill site, as any benefit would be very small.
2.7.3 Other costs and considerations
One of the key beneficial uses for MWOO identified above would be its use as capping material,
including in a phytocap. Phytocaps require a design specific to the area and climate conditions for
each landfill to be capped, taking into regard soils, precipitation, landfill gas generation, etc. This also
requires testing and approvals, which will be more costly to manage than a conventional cap.
According to Biomass Solutions, the density of MWOO fluctuates between 500 and 800 kg/cbm, but
on average one can assume 650 kg/cbm.
A consideration for interim cover could be trafficability of the MWOO, when applied at 300mm, in
particular in wet weather events. Driving over an interim cover of MWOO may impact its performance
as a biocover due to the ensuing compaction. The practical application will have to be tried and
should be subject to design considerations, which can be considered in the phytocap design
considerations. MWOO may have to be mixed with available site soils (phyllite) in order to ensure the
interim cover remains trafficable. As the region of Nambucca/Bellingen is known for heavy wet
weather events, the mixture and/or design of an interim may require special consideration. The
potential for erosion, in particular during wet weather events, will have to be considered.
Nevertheless, MWOO should still be usable as a daily cover, as this would be applied at the end of a
working day and stripped off at the beginning of every working day in line with best practice
operations.
As an example of the increased management and monitoring requirements, see the licence for
Lismore Council’s Wyrallah Road Landfill (EPL 5880, attached) and the specific regulations for
phytocaps in Section 9.4 of the NSW EPA Environmental Guidelines for Solid Waste Landfills (also
attached).
The use of MWOO as daily or interim cover or as a phytocap would require a variation of the current
EPL. The EPA will most likely require trials and a specific design for a phytocap. However,
experiences from the Lismore landfill can be drawn upon. Lismore has a long-term average rainfall of
1,343mm, whereas Nambucca has 942mm and Bellingen 1,517mm. The areas can be seen as
comparable.
Both Nambucca and Bellingen landfills are currently not accepting putrescible waste. The landfill gas
generation might therefore be minimal. However, landfill gas will still be produced and any reduction
of the methane potential will be a benefit.
Any additional costs connected with using a phytocap, such as specific design, trials and laboratory
tests, and EPA approval processes, are at this stage difficult to ascertain, but in our estimate would
amount to tens of thousands of dollars rather than hundreds of thousands. We will endeavour to
obtain reasonable cost estimates during the time of this overall strategy assessment, but have
released this short report in its current form in the interest of facilitating an immediate response to the
challenge with CHCC and BIO.
2.7.4 Approval of phytocap
Without pre-empting what the EPA might require in regard to design and studies, it is noted that due
to the relatively high rainfall in both Nambucca and Bellingen, the EPA will most likely require large
scale trials and also require a site specific Resource Recovery Order and Exemption. The process will
take some time and considering that cell 3 of stage 1 at Nambucca landfill will be full around 2024,
time might be of the essence. Any approval for utilising MWOO for the unlined landfills of BSC may be
rather difficult to obtain.
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Management options for mixed waste organics outputs
3 DISCUSSION OF KEY FINDINGS
The assessment of comparative benefits for the use of MWOO demonstrate some clear benefits
compared to the conventional cap. They are as follows:
• Stabilisation of the organic fraction of the MSW prior to landfilling reduces biodegradability by up
to 50%, delivering a range of environmental benefits, including a much more controlled odour
profile of otherwise putrescible waste.
• There are clear benefits in the use of mature MWOO as daily or interim landfill cover. It will yield
a smaller GHG emission footprint since it is not subject to anaerobic conditions and therefore will
not generate methane (CH4) within the landfill pile, but mostly lower carbon intensive CO2.
Leachate production is also reduced, addressing another key environmental impact associated
with landfill.
• One key benefit of the daily or interim cover option is it makes use of the biofilter potential of
MWOO, supporting bacterial activity for odour suppression and methane (landfill gas) oxidisation.
These qualities are also beneficial in a phytocapping context, replacing more expensive compost
and other soil products in closure operations.
• The use of MWOO in a landfill context as daily or interim cover or as part of a phytocap design
also leads to significant cost savings, in particular in those cases where cover materials otherwise
would need to be imported.
There is a strong evidence base to support the use of MWOO in a landfill context, such as daily,
interim or part of a final cover, which offers a range of environmental benefits when compared to
disposing of MSW directly to landfill as well as financial benefits when compared to using engineered
final cover materials.
It is also noted that NVC and BSC should consider sharing portions of this report with CHCC, at
minimum to engender support for the use of MWOO as landfill cover and capping material. It may be
the case that CHCC may become a benefactor of the same MWOO solution by using it as capping
material for its Englands Road Landfill. This approach of “finding a win-win solution” could also be
used to help negotiate an outcome of the MWOO dispute which is acceptable to both NVC and BSC.
1
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