Site search

Search

Recommendations for methodologies for ETS landfill gas emission reporting

Executive summary

This report has been prepared by Tonkin & Taylor Ltd for the Ministry for the Environment. It provides recommendations on methodologies and default parameters for inclusion in:

• The Climate Change (Disposal Facilities) Regulations 2010, specifying a simple default methodology
• An amendment to the existing Climate Change (Unique Emissions Factors) Regulations 2009, providing the three non-default methods.

The following methods are proposed for waste disposal facility operators to calculate their emission obligations under the Emissions Trading Scheme:

• Default method – emissions calculated using Equation 1 with no requirements for site specific data
• Non-default method 1 – emissions calculated using Equation 4 and Equation 5 to take into account site specific waste composition data
• Non-default method 2 – emissions calculated using Equation 6, Equation 7 and Equation 8 to take into account methane destruction in a flare or utilisation equipment
• Non-default method 3 – emissions calculated using Equation 8, Equation 9, and Equation 10 to take into account site specific waste composition data and methane destruction in a flare or utilisation equipment.

Default values used in the assessment of emissions are taken from values used in the New Zealand National Greenhouse Gas Inventory and supplemented with international standards as appropriate.

1 Introduction

Tonkin & Taylor (T&T) was engaged by the Ministry for the Environment (MfE), under Contract Number 13298, to recommend appropriate methodologies for the estimation of methane emissions from landfills for incorporation into regulations that will specify how waste disposal facility operators (DFOs) who are Emissions Trading Scheme (ETS) participants will meet their reporting commitments.

In particular this report provides:

• Recommendations for the emissions factor for the default method including default values for methane correction factor, waste composition and degradable organic content
• Recommendations for the default values for methane correction factor, degradable organic content and requirements for ongoing demonstration of validity for the non-default method which allows a DFO to use site specific waste composition data to determine emissions
• Recommendations for the default destruction factors for common destruction equipment, methane generation assessment, requirements for monitoring quantity of methane destroyed and for ongoing demonstration of viability for the non-default method which allows a DFO to determine the destruction efficiency of their landfill gas management system
• The results of a literature review together with recommendation for the default value for methane oxidation through landfill covers.

1.1 Landfill methane emissions

Waste emits methane and other landfill gases over time as it decomposes. The amount of methane that is eventually emitted depends on factors such as the composition of the waste, whether any methane is captured and destroyed, and the management of the cap material at the facility.

Methane emissions from landfills (waste disposal sites) are included in the Climate Change Response Act 2002 (CCRA). Voluntary reporting of methane emissions for the ETS will begin on 1 January 2011. Regulations for reporting must therefore be developed to specify the methodologies for calculation of methane emissions in advance of that date.

1.2 Waste Technical Advisory Group

A Technical Advisory Group (TAG) for Waste, made up of expert stakeholders and officials, reported on preferred policy options and methods for determining and reporting landfill methane emissions for ETS purposes in their report dated March 2010 (ETS Waste TAG, 2010). This report has provided the basis of the methodologies developed for calculation of methane emissions from landfills for inclusion in the ETS.

The TAG recommended that a simple default methodology be provided with default factors to provide a minimal compliance cost option. This is particularly important for smaller landfills or landfills with limited scope for reducing emissions. It was further recommended that additional non-default methodologies with unique emissions factors (UEF) be provided to recognise and encourage emission reductions and accurate monitoring, such as landfill gas collection and destruction. Justification for the use of these non-default methodologies would be provided by the DFOs. These recommendations are in line with methods used for other sectors in the ETS.

The TAG recommended that the default methodology be based on the mass balance method for estimating emissions from landfills. This method estimates the total methane emission from waste placed, assigning it to the year it is disposed of in the landfill. The non-default methodologies would allow for proven variation in waste composition, collection and destruction of landfill gas, and oxidation of methane through landfill capping materials.

2 Proposed approach

The recommended methodology for disposal facility methane emissions is based on placing the obligation, to report these emissions, on the DFO in the year that the waste is disposed. Emissions derived from waste already disposed, before the regulations come into effect, are not reported. Emissions that will actually occur in future years are reported ahead of time, in the year that the waste which will generate the emissions is disposed.

A default methodology is required, offering a simple option for reporting emissions based on data that already has to be collected and submitted for compliance with the Waste Minimisation Act 2008. This will incorporate a default assessment based on:

• Methane potential per tonne of waste disposed, reflecting the waste composition (specifically the amount of degradable organic carbon (DOC) in the waste) and the fraction of this carbon that decomposes to methane with the default composition based on national survey data published by the MfE
• No allowance for collection or destruction of landfill gas
• An allowance for partial oxidation of methane as it diffuses through the cap material based on the 10% oxidation of total methane generated as reported in the National Greenhouse Gas Inventory.

Optional non-default methods will also be included. These will allow DFOs to account for site specific waste composition and/or the reduction in emissions that a DFO can achieve by collecting and destroying methane. The site specific waste composition will be established by site specific sampling and analysis. The methane destruction efficiency will be assessed by comparing the results of a site specific landfill gas generation assessment against destruction data. Use of the default assumption of a 10% oxidation rate, however, will be mandatory.

The regulations will comprise:

• The Climate Change (Disposal Facilities) Regulations 2010, specifying a simple default methodology
• An amendment to the existing Climate Change (Unique Emissions Factors) Regulations 2009, providing the three non-default methods.

Where possible it is recommended that data collection requirements are aligned to those required for the calculation and payment of the Waste Disposal Levy.

3 Default method

We recommend that the Regulations require DFOs to use Equation 1 to calculate emissions if the default method is selected.

Equation 1
E_A = 1.1454 × A_A

Where:

A_A is the tonnes of waste disposed to the facility in the year

E_A is the emissions in tonnes of carbon dioxide equivalent (tCO₂e) for the year

3.1 Waste tonnage - A_A

It is recommended that waste tonnage is determined using the methods in the Waste Minimisation (Calculation and Payment of Waste Disposal Levy) Regulations 2009, which will take into account disposal facilities with and without on site weighbridges and include all waste disposed at facilities other than diverted tonnage.

3.2 Background to emission factor selected

The emission factor in Equation 1 has been calculated as follows:

Equation 2
DEF = (MCF × DOC_f × F_CH4 × 16/12 × GWP × DOC) × (1 – OX)

Where:

Methane correction factor (anaerobic managed fill) (refer to Section )	MCF = 1
Fraction of DOC that degrades to methane	DOCf = 0.5
Fraction of landfill gas (by volume) that is methane	FCH4 = 0.5
Molecular unit weight ratio of CH4 : CO2	16/12
Global warming potential of methane	GWP = 21
Adjustment for methane oxidation through capping system	(1 – OX) = 0.9

Resulting in:

DEF = (1 × 0.5 × 0.5 × 16/12 × 21 × DOC) × 0.9 = 6.30 ×DOC

Where:

Degradable organic content of combined waste stream is calculated by Equation 3 using values from Table 1.

DOC = 0.1818

Equation 3
DOC = [(0.15 × 0) + (0.2 × 0.233) + (0.4 × 0.149) + (0.43 × 0.139) + (0.24 × 0.039) + (0.24 × 0.027) + (0.05 × 0)

Table 1 Default composition and DOC values

Waste stream component1	IPCC DOC	SWAP 2004 percentage
Food	0.15	0.0%
Garden	0.2	23.3%
Paper	0.4	14.9%
Wood	0.43	13.9%
Textile	0.24	3.9%
Nappies	0.24	2.7%
Sewage sludge2	0.05	0.0%
Other	0.0	41.3%

3.2.1 Methane correction factor

The International Panel on Climate Change (IPCC) guidelines (IPCC, 2006) define the methane correction factor (MCF) based on the percentage of anaerobic degradation. The higher the MCF the more anaerobic degradation and the corresponding less aerobic degradation is assumed to occur at a specific facility.

The classifications included in the IPCC 2006 guidelines include:

• Anaerobic managed solid waste disposal sites: Sites where there is controlled placement of waste (ie waste directed to specific deposition areas, a degree of control of scavenging and a degree of control of fires) and include at least one of the following: (i) cover material; (ii) mechanical compacting; or (iii) levelling of the waste. As a result all degradation is assumed. (MCF = 1)
• Semi-aerobic managed solid waste disposal sites: Sites where there is controlled placement of waste and measures are provided to enable the introduction of air into the waste layer such as: (i) permeable cover material; (ii) leachate drainage system; (iii) regulating pondage; and (iv) gas ventilation system. (MCF = 0.5)
• Unmanaged solid waste disposal sites – deep and/or with high water table: Sites not meeting the criteria of managed sites and which have depths of greater than or equal to 5 metres and/or high water table at near ground level. (MCF = 0.8)
• Unmanaged shallow solid waste disposal sites: Sites not meeting the criteria of managed sites and which have depths of waste of less than 5 metres. (MCF = 0.4)

The National Greenhouse Gas Inventory currently assumes that all landfills in New Zealand are anaerobic managed solid waste disposal sites (ie MCF = 1). However, values prior to 2010 assume a gradual change from 90% managed fills and 10% unmanaged fills (MCF = 0.96) to 100% managed fills (MCF = 1.0) between 1996 and 2009.

4 Non-default methods

4.1 Non-default method 1

Non-default method 1 allows a DFO to use site specific waste composition data to determine emissions. Details of how the site specific waste composition data is determined and validated are included in Section .

We recommend that the Regulations require DFOs to use Equation 4 and Equation 5 to calculate emissions if the non-default method 1 is selected.

Equation 4
E_A = EF₁ × A_A

Where:

A_A is the tonnes of waste disposed to the facility in the year
E_A is the emissions in tCO₂e for the year
EF₁ is a Unique Emissions Factor (UEF) allowing for site specific waste composition calculated by Equation 4, using the default DOC values from Table 1

Equation 5

EF₁ = 6.30 × [(0.15 × FW) + (0.2 × GW) + (0.4× PW) + (0.43 × WW) + (0.24 × TW) + (0.24 ×NW) + (0.05 × SW)]

Where:

FW is the fraction of food waste
GW is the fraction of garden waste
PW is the fraction of paper waste
WW is the fraction of wood waste
TW is the fraction of textile waste
NW is the fraction of nappy waste
SW is the fraction of sewage sludge waste

4.2 Non-default method 2

Non-default method 2 allows a DFO to take into account the amount of methane that is collected and destroyed at a particular site. Details of how the site specific methane destruction efficiency are validated are included in Section .

We recommend that the Regulations require DFOs to use Equation 6, Equation 7 and Equation 8 to calculate emissions if the non-default method 1 is selected.

Equation 6
E_A = EF₂ × A_A

Where:

A_A is the tonnes of waste disposed to the facility in the year
E_A is the emissions in tCO2e for the year
EF2 is a Unique Emissions Factor (UEF) allowing for methane destruction and collection calculated by Equation 7

Equation 7
EF₂ = 1.1454 × (1-C)

Where:

C is the efficiency of the methane destruction system calculated by Equation 8

Equation 8
C = D × Q/G

Where:

C is the methane destruction efficiency
D is the destruction factor for the type of destruction equipment used (Section )
Q is the metered quantity of methane destroyed (Section )
G is the estimated gross methane generation (Section )

4.3 Non-default method 3

Non default method 3 allows a DFO to take into account site specific waste composition and the amount of methane that is collected and destroyed at a particular site (ie combines non-default methods 1 and 2).

We recommend that the Regulations require DFOs to use Equation 8, Equation 9 and Equation 10 to calculate emissions if the non-default method 1 is selected.

Equation 9
E = EF₃ × A_A

Where:

A_A is the tonnes of waste disposed to the facility in the year
E is the emissions in tCO₂e for the year
EF₃ is a Unique Emissions Factor (UEF), calculated by Equation 10

Equation 10
EF₃ = 6.30 × [(0.15 × FW) + (0.2 × GW) + (0.4× PW) + (0.43 × WW) + (0.24 × TW) + (0.24 ×NW) + (0.05 × SW)] × (1-C)

Where:

FW is the fraction of food waste
GW is the fraction of garden waste
PW is the fraction of paper waste
WW is the fraction of wood waste
TW is the fraction of textile waste
NW is the fraction of nappy waste
SW is the fraction of sewage sludge waste
C is the methane destruction efficiency calculated by Equation 8

5 Non-default waste composition

To determine the composition of the waste and calculate the Unique Emissions Factor (non-default methods 1 and 3), site specific waste must be sampled, and the fraction of each component of the waste estimated. We recommend that the sampling and analysis methodologies outlined in the Solid Waste Analysis Protocol (SWAP) (MfE 2002a and 2002b) are used to determine the composition of the waste.

We recommend a combination of sort-and-weigh and visual classification methodologies be used. This will enable detailed surveys to be used to establish the waste composition through the sort-and-weigh method. The less onerous visual classification can then be undertaken to maintain confidence in the ongoing use of the estimated fractions of each component.

5.1 Requirements for application for non-default waste composition

SWAP Procedure 2 (MfE 2002b) outlines the general process for estimating the composition of waste entering a disposal facility. The procedure involves weighing most large vehicle loads entering the site, sampling a proportion of incoming loads from each waste source, sorting and weighing the waste, and statistical analysis and reporting. We recommend that this procedure is adopted for the composition assessment. The waste received at the facility shall be analysed by source to determine the percentage of components listed in Table 2. The separation of the SWAP analysis into waste source will enable the DFO to adjust the emission factor each year to take into account actual weighbridge data from each waste source.

Table 2 Composition data (percentage by weight)

Waste source1		Waste components2
	% Total	Food	Garden	Paper	Wood	Textile	Nappies	Sewage sludge	Other	Total
Municipal Solid Waste (MSW)										100%
Commercial & Industrial (C&I)										100%
Building & Demolition (B&D)										100%
Other3										100%
Total	100%

The composition analysis must reflect the average composition of the individual waste components entering the facility. Although it is noted that the SWAP document (MfE 2002b) recommends four waste surveys in a single year for baseline composition data the TAG recommended that a minimum of two waste sort and weigh surveys over a 12 month period would be sufficient for the ETS regulations.

Surveys shall be carried out at least three months apart, to allow for effects of seasonal variation. Surveys shall collect data over a minimum period of one week to account for weekly patterns of waste composition.

The SWAP recommends a sample size for the sort-and-weigh method of 300-500 vehicles. This would result in a precision of ±10 to 20% for each primary waste category. However, this may exceed the number of vehicles using small sites during the survey period. We therefore recommend that the Regulations require the sampling to be representative. As part of the Unique Emissions Factor approval process the representativeness of the sample will be verified.

Further information on this is provided in the SWAP guidelines (MfE 2002a and 2002b).

5.2 Requirements for demonstration of ongoing validity of non-default waste composition

We recommend that the DFO is required to re-establish the composition of each waste source at 10 yearly intervals by undertaking the same process as originally used to demonstrate site specific composition.

The DFOs are responsible for verifying that the waste composition data remains valid. The Regulations should require the DFO to undertake a visual classification of the waste if the waste composition changes significantly (if, for example, a local composting plant closes down and greenwaste is diverted to the facility) with a maximum time between visual inspections of 5 years. In the event of variation, additional surveys would be required to re-establish the waste composition.

During the intermediate years, the source of the waste shall be provided (eg by weight or total count of trucks from each waste source). The annual fraction of each waste component can then be calculated for insertion into Equation 5 or Equation 10 (as appropriate).

6 Methane destruction efficiency

The methane destruction efficiency (Equation 8) is the percentage of methane collected and destroyed in a flare or utilisation equipment. It takes into account the destruction factor of the equipment being used (ie the amount of methane that is destroyed by the utilisation equipment) and the collection efficiency of the landfill gas management system.

The collection efficiency of the landfill gas management system is the percentage of the landfill gas that is collected. It is determined by the coverage of the system at any one time and the collection efficiency of individual wells. The well efficiency is not only a function of the effectiveness of the individual collection wells but also factors such as landfilling methods, depth of waste, leachate saturation levels, and cover permeability.

To determine a site specific collection efficiency DFOs need to estimate the amount of methane being generated in any one year (G) and compare that against the methane collected and destroyed in the same year (Q). The mass balance model recommended for the ETS estimates the total potential methane generation of the waste placed and allocates it to the year of waste placement. It does not reflect actual generation by year therefore cannot be used for the generation estimate. However, a first order decay model estimates the actual methane generation at any one time and can therefore be used to estimate methane generation in the target period (G). The value of G can then be compared with the methane collection over the target period (Q) to determine the collection efficiency.

We recommend that the estimated gross generation of methane (G) be calculated using a first order decay model, as set out in the IPCC guidelines (IPCC , 2006) and used in the National Greenhouse Gas Inventory, or similar. The metered quantity of methane (Q) is recorded by annually calibrated meters at the point of destruction of the methane.

The following sections outline how a DFO would demonstrate a site specific methane destruction efficiency.

6.1 Default destruction factor - D

There is limited information in the International regulatory arena for destruction efficiency of common destruction equipment. The Clean Development Mechanism (CDM) Executive Board of the United Nations Framework Convention on Climate Change (UNFCCC) is one regulatory body that has published destruction factors for open and enclosed flares (Table 3).

Table 3 Default destruction factor, D

Destruction equipment1	Destruction factor, D
Open flare2	0.5
Enclosed flare2	0.9
Internal combustion engines, gas turbines, boilers 3	0.9

Recent industry lead research (GE AES, 2008 and SCS, 2007) suggests that the recommended default destruction factors are conservative (SCS, 2007 states that both enclosed flares and internal combustion engines are more likely to have values around 0.98). However, as this is industry lead research it is unlikely to be able to be adopted for default values in the Regulations. We consider the CDM values as extremely conservative and therefore recommend that the Regulations allow the DFO to use either the default values listed in Table 3 or site specific manufacturer’s data provided they can demonstrate the applicability of the data to the specific facility.

6.2 Metered quantity of methane destroyed – Q

The quantity of methane destroyed will be determined by direct measurement of landfill gas flow rate and methane concentration. We therefore recommend that the Regulations require the flow and the methane concentration of the landfill gas conveyed to the destruction equipment (flare or utilisation equipment) to be recorded by the DFO. The meters shall be selected and installed in accordance with the equipment manufacturer’s recommendations.

We understand that similar regulations require monitoring at least every half hour for 90% of the hours of the year. Such criteria are considered appropriate for this application. The total flow and average composition can be determined by extrapolating between data points to a reasonable level of accuracy.

Any landfill gas conditioning such as condensate traps and contaminant filters (eg particulates or trace gas removal such as hydrogen sulphide) shall be provided upstream of the equipment in accordance with equipment manufacture’s recommendations. The detection limits of the equipment shall be within the range that is likely to be reasonably assumed by the DFOs for their specific facility.

The data from the meters shall be automatically logged and retained by the DFO for a minimum of 10 years.

All equipment shall be calibrated yearly and serviced in accordance with the equipment manufacturer’s recommendations.

6.3 Estimated gross methane generation - G

We recommend that the DFOs are required to set up a first order decay model based on the following IPCC 2006 equations to determine the methane generation potential of the waste:

Equation 11
DDOCma_T = DDOCmd_T + (DDOCma_T-1 • e^-k)

Equation 12
DDOCm decomp_T = DDOCma_T-1 (1- e^-k)

Equation 13
G = DDOCm decomp_T • F • (16/12)

Where:

T is the emission year
DDOCma_T is the mass of decomposable DOC accumulated at the end of year T in tonnes
DDOCma_T-1 is the mass of decomposable DOC accumulated at the end of year (T-1) in tonnes
DDOCmd_T is the mass of decomposable DOC deposited in year T in tonnes
DDOCm decomp_T is the mass of decomposable DOC decomposed in year T in tonnes
k is the reaction constant
G is amount of CH₄ generated from decomposable material
F is the fraction of CH₄, by volume, in generated landfill gas
16/12 is the molecular weight ratio of CH₄/C

These equations form the basis of the IPCC Waste Model (IPCC, 2006) which is in the form of an Excel Spreadsheet which can be used directly by DFO’s.

Alternatively, we recommend that the regulations allow the DFOs to use a first order decay model of their choosing, such as the Scholl-Canyon Model, provided they use the default input parameters.

The modelling will need to start from when the facility started accepting waste to enable the decomposition of waste already in place to be taken into account. Ideally, accurate composition and tonnage data shall be used in the model. However, the DFOs may not have accurate composition and tonnage data for waste over the life of the landfill (ie prior to implementation of the ETS). Therefore, we recommend that where accurate data is not available the Regulations require the DFOs to adopt the following default assumptions:

• Waste composition as per the regulation default (ie Table 1 data) for waste disposed in historical (pre-reporting) years
• Waste composition as per the regulation default for reporting years in which the default composition is in use for reporting emissions
• A non-default waste composition for waste disposed in reporting years for which the non-default composition was approved and in use for reporting emissions in the same year
• Tonnage based on an average filling rate over the life of the landfill up to the first year in which weighbridge data is available
• Tonnage based on weighbridge data for years in which weighbridge data was collected.

The model shall then be calibrated against landfill gas collection data for as many years as the DFO has data available and adjusted if necessary thereby reducing the impact of input assumptions.

6.3.1 First order decay model input parameters

A first order decay model, whether the IPCC Waste Model or an alternative, requires an estimate of the time it takes for anaerobic generation to commence and consequently the onset of methane generation. The National Greenhouse Gas Inventory uses the IPCC default value of 6 months. There are some facilities in New Zealand where this value may not accurately reflect the specific site conditions. However, on balance, we recommend that this value is likely to reflect a reasonable estimate and should therefore be the default value in the Regulations.

If the IPCC Waste Model is used, the oxidation factor through the cover system shall be assumed as the same as the default ie 10%.

The IPCC Waste Model provides two options for the estimation of emissions from waste, namely:

• A multi-phase model based on waste composition data
• A single-phase model based on bulk waste data.

As there is no New Zealand specific decomposition data we recommend that the Regulations require the DFOs to use the IPCC 2006 DOC and associated L_o values, and k values in the landfill gas generation assessment irrespective of whether they use the IPCC Waste Model or an alternative first order decay model. These default values are provided in Table 4.

Table 4 First order decay model input parameters

Waste stream component	Default waste composition data (SWAP 2004)	IPCC DOC	Equivalent methane generation potential1 Lo (m3 CH4 / tonne)	Decay rate constant2 k
Food	0.0%	0.15	75	0.185
Garden	23.3%	0.2	100	0.1
Paper	14.9%	0.4	200	0.06
Wood	13.9%	0.43	215	0.03
Textile	3.9%	0.24	120	0.06
Nappies	2.7%	0.24	120	0.1
Sewage sludge3	0%	0.05	25	0.185
Other	41.3%	0.0	0	0

If using non-default method 2 the DFO shall use default composition waste composition (ie Table 1 data) for the generation assessment. Non-default method 3 combines the estimation of waste composition with the efficiency of collection and destruction of methane. Therefore, the site specific waste composition data can be directly input into the methane generation model.

The bulk national composition data and associated Lo values used in the National Greenhouse Gas Inventory for years prior to 2004 are summarised in Table 5.

Table 5 National Greenhouse Gas Inventory DOC and associated Lo values

Year	Degradable organic carbon	Equivalent Lo (m3 CH4/tonne)
Prior to 1996	0.14571	73
1996	0.14843	74
1997	0.15114	75
1998	0.15386	77
1999	0.15658	78
2000	0.15929	79
2001	0.16201	81
2002	0.16473	82
2003	0.16744	84
2004 to present	0.17016	85

6.4 Requirements for demonstration of ongoing validity of destruction efficiency

We recommend that the DFOs be required to update the landfill gas generation model each year. This will require them to demonstrate that the assumed destruction efficiency is valid and forms part of the annual monitoring plan. If there is any significant variance in the resulting unique emissions factor the DFOs shall be required to reapply. This approach is considered simpler than requiring DFOs to demonstrate that the areas or proportions of waste covered by the landfill gas collection system have not significantly changed. Furthermore this would negate the need for estimating areas of different cover materials^{Footnote 1}.

We recommend that in addition to the generation and collection calculation that DFOs are required to test surface emissions of methane to further substantiate that the destruction efficiency is realistic. The Landfill Guidelines (CAE, 2000) provide some advice on surface emission monitoring techniques. However, more detailed requirements are outlined in the UK Environment Agency Guidance on monitoring landfill gas surface emissions. We recommend this document be referenced to provide a structure to the surface emissions testing. We recommend that the emission testing is undertaken every five years and as part of the application process for the unique emissions factor.

7 Issues for future consideration

7.1 Oxidation factor

There is significant peer reviewed international literature which demonstrates that bacteria within a landfill cover oxidises methane and other hydrocarbons from the landfill gas as it passes through. This process reduces the emissions of methane and other hydrocarbons from the landfill surface (Chanton et al, 2009). Currently the default value for oxidation of methane in the cover system for national greenhouse gas inventories is 10% of the generated methane (IPCC, 2006).

Adoption of the default oxidation factor in the ETS is likely to result in an overestimation of the emissions from facilities which are well managed and use appropriate cap materials. However, we have not been able to identify any New Zealand specific data or internationally accepted standards which we could reference and determine an alternative value for recommendation.

International research has been undertaken into varying oxidation factors for different capping materials. However, these results may not adequately reflect New Zealand conditions. Furthermore, although procedures have been developed to estimate varying oxidation factors, there are no internationally accepted standards which can be referred to in the ETS Regulations. Currently, the technology available for the direct measurement of methane emissions from landfill caps is insufficient to give reliable estimations of the actual oxidation factors.

Consequently, we recommend the ETS Regulations adopt a default oxidation factor of 10%. As sampling technology and research into this area advances, this should be revisited to allow for higher oxidation factors to be used where well managed landfills can provide sufficient evidence for them.

It is our understanding that the Act is to be reviewed in 2011. We therefore recommend that, If the 2011 review results in the inclusion of closed landfills and a first order decay method was deemed more appropriate than mass balance, and if further national or international work has been performed that provides greater certainty on oxidation methods and possible default values for cover types, officials should revisit the policy decision to allow only a default oxidation rate to be used.

7.2 Unique emission factor for anticipated emissions

The TAG report recognised:

“Due to the uncertainties inherent in estimating waste composition, waste degradation, gross generation of methane, and methane oxidation, it is foreseeable that some facilities could want an option to estimate ‘anticipated emissions’ using a set of reliable actual emission data. It is suggested that the regulations also provide this option, while recognising that it would not likely be used until further advances in technologies and understanding can support it.”

It is our understanding that it is not proposed to include this approach in the current Regulations as relevant international standards have not been identified. We therefore recommend that if, as outlined above, the 2011 review results in an first order decay method being adopted and if further national or international work has been performed that provides suitable international standards then officials should revisit the policy decision to allow such an approach.

8 References

CAE, 2000, Landfill Guidelines, Towards sustainable waste management in New Zealand

Chanton JP, Powelson DK, Green RB, 2009 Methane oxidation in landfill cover soils, is a 10% default value reasonable?, J Environ Qual, 38:654-663

ETS Waste TAG, 2010, Report of the New Zealand Emissions Trading Scheme Waste Technical Advisory Group, March 2010

GE AES Greenhouse Gas Services, 2008, Methodology for Landfill Gas Methane Capture and Destruction Projects, Version 1.1 – November 10, 2008

Hendtlass, Charles (ed), Landfill Guidelines, 2000, Centre for Advanced Engineering, Canterbury

IPCC 2006, Guidelines for national greenhouse inventories, available at http://www.ipcc-nggip.iges.or.jp/public/2006gl/index.html, Intergovernmental Panel on Climate Change, Geneva, Switzerland

Ministry for the Environment, 2002a, Solid Waste Analysis Protocol, Summary Procedures, March 2002

Ministry for the Environment, 2002b, Solid Waste Analysis Protocol, March 2002

SCS Engineers, 2007, Current MSW Industry Position and State of the Practice on Methane Destruction Efficiency in Flares, Turbines, and Engines, Presented to: Solid Waste Industry for Climate Solutions (SWICS)

UK Environment Agency, Landfill directive LFTGN 07, Guidance on monitoring landfill gas surface emissions, 2004

9 Applicability

This report has been prepared for the benefit of the Ministry for the Environment with respect to the particular brief given to us and it may not be relied upon in other contexts or for any other purpose other than that for which it was specifically prepared without our prior review and agreement.

Tonkin & Taylor Ltd
Environmental and Engineering Consultants
Report prepared by: Simonne Eldridge, Project Manager
Authorised for Tonkin & Taylor by: Keith Dickson, Project Director

---

Availability

• Download PDF
  (373 KB)
• Problems with PDFs?

This site is administered by the Ministry for the Environment.