11

Estimating Global Methane Estimating Global Methane Emissions from LandfillsEmissions from Landfills

W. Gregory VogtW. Gregory VogtSanitary Landfill Working Group Sanitary Landfill Working Group

7 November 2006, 7 November 2006, RiminiRimini

22

Topics to be CoveredTopics to be CoveredBackground on methane emissions from landfills and Background on methane emissions from landfills and dump sitesdump sites

IPCC methods for calculating global methane emissions IPCC methods for calculating global methane emissions from landfillsfrom landfills

Use of a modified IPCC method (Use of a modified IPCC method (BognerBogner and Matthews, and Matthews, 2003) to estimate global landfill methane emissions 2003) to estimate global landfill methane emissions through 1996through 1996

Extrapolate results to estimate global methane Extrapolate results to estimate global methane emissions through 2006emissions through 2006

33

Landfills and Landfill BiogasLandfills and Landfill Biogas

Landfill biogas is approximately 50Landfill biogas is approximately 50--60% 60% methane and 40methane and 40--50% CO50% CO22

Methane is 21 more times more potent GHG Methane is 21 more times more potent GHG than COthan CO22

Biomass derived COBiomass derived CO22from landfills is not from landfills is not “counted” as contributing “counted” as contributing to global warming by to global warming by UNFCCCUNFCCC

44

Waste Decay and Methane Waste Decay and Methane Generation in LandfillsGeneration in Landfills

Engineered and Sanitary LandfillsEngineered and Sanitary Landfills•• Soil cover and waste compaction Soil cover and waste compaction -- anaerobic anaerobic

conditions quickly establishedconditions quickly established

•• Long, stable period of production of methane and COLong, stable period of production of methane and CO22

Dump SitesDump Sites•• Limited/no soil cover or waste compaction Limited/no soil cover or waste compaction –– aerobic aerobic

conditions persistconditions persist

•• Long period (perhaps years) before waste burial Long period (perhaps years) before waste burial creates anaerobic conditions and significant methane creates anaerobic conditions and significant methane is generatedis generated

55

Dump Sites Dump Sites –– Environmental IssuesEnvironmental IssuesAerobic conditions predominate and lead to:Aerobic conditions predominate and lead to:

•• High landfill temperatures High landfill temperatures and landfill firesand landfill fires

•• High carboxylic acid High carboxylic acid concentrations (BOD) in concentrations (BOD) in leachateleachate

•• Poor drainage leads to Poor drainage leads to leachate runoff into leachate runoff into surface and groundwatersurface and groundwater

66

Methane Emissions: Methane Emissions: Developed CountriesDeveloped Countries

Methane emissions decreasing due to:Methane emissions decreasing due to:•• Waste generation is stabilizingWaste generation is stabilizing•• Limits to landfill space; future limits to organics Limits to landfill space; future limits to organics

disposaldisposal

•• Increases in recycling and Increases in recycling and composting composting

•• Increases in methane Increases in methane recovery from landfillsrecovery from landfills

77

Methane Emissions: Methane Emissions: Developing CountriesDeveloping Countries

Methane emissions increasing due to:Methane emissions increasing due to:•• Increases in population and urbanizationIncreases in population and urbanization•• Increases in waste generationIncreases in waste generation•• Conversion from dump sites to Conversion from dump sites to

landfills landfills –– a plus for environment a plus for environment but causes increased methane but causes increased methane generationgeneration

•• Passive venting of landfill biogas is Passive venting of landfill biogas is a common practicea common practice

•• Insignificant methane recovery due Insignificant methane recovery due to limited knowledge and fundingto limited knowledge and funding

88

Methane Emissions from Methane Emissions from Landfills Landfills -- OverviewOverview

Range of estimates of global landfill Range of estimates of global landfill methane emissions: 9 methane emissions: 9 –– 70 70 TgTg/year/yearMethane mass balance:Methane mass balance:•• CHCH44 Production = Production =

CHCH44 Emitted + Emitted + CHCH44 Oxidized + Oxidized + CHCH44 Recovered + Recovered + Lateral CHLateral CH44 Migration Migration + + ∆∆CHCH44 StorageStorage

99

Methodologies for Estimating Methodologies for Estimating Global Methane EmissionsGlobal Methane Emissions

Limited field data on measured methane Limited field data on measured methane emissions emissions –– empirical models for empirical models for methane recovery onlymethane recovery onlyAnnual methane emissions from each Annual methane emissions from each country are estimated based on waste country are estimated based on waste disposal data disposal data •• IPCC methodology (“Tier 1” method)IPCC methodology (“Tier 1” method)•• FirstFirst--order decay models (“Tier 2” method)order decay models (“Tier 2” method)

1010

IPCC Method (Tier 1)IPCC Method (Tier 1)CHCH44 emitted (emitted (TgTg/yr) = /yr) = {[({[(MSWMSWtt)(MSW)(MSWff)(MC)(MCff) )

(DOC)(DOC(DOC)(DOCff)(F)(16/12)] )(F)(16/12)] -- R}(1 R}(1 –– OX),OX),Where:Where:•• MSWMSWtt = Municipal solid waste generated= Municipal solid waste generated•• MSWMSWFF = Fraction of generated MSW disposed in landfills= Fraction of generated MSW disposed in landfills•• MCMCFF = Fraction of = Fraction of landfilledlandfilled MSW which decomposes MSW which decomposes

anaerobicallyanaerobically (“correction factor”)(“correction factor”)•• DOC = Fraction of biodegradable organic carbon in DOC = Fraction of biodegradable organic carbon in

landfilledlandfilled MSWMSW•• DOCDOCff = Fraction of DOC “dissimilated” (converted to CH= Fraction of DOC “dissimilated” (converted to CH44

and COand CO22 in landfill biogas)in landfill biogas)•• F = Fraction of CHF = Fraction of CH44 in landfill biogasin landfill biogas•• R = Amount of recovered CHR = Amount of recovered CH44

•• OX = Fraction of CHOX = Fraction of CH44 oxidized in cover soilsoxidized in cover soils

1111

Advantages of IPCC MethodAdvantages of IPCC Method

Minimizes data requirementsMinimizes data requirements•• Annual waste generation can be derived Annual waste generation can be derived

from waste generation per capita estimates from waste generation per capita estimates (where data are lacking)(where data are lacking)

•• IPCC guidance and IPCC guidance and default values for default values for terms in equation terms in equation

1212

Disadvantages of IPCC MethodDisadvantages of IPCC Method

Estimates based on current year’s disposalEstimates based on current year’s disposal•• Do not account for methane from prior years’ wasteDo not account for methane from prior years’ waste•• Do not account for waste decay rates (wide range Do not account for waste decay rates (wide range

depending on types of waste, moisture content)depending on types of waste, moisture content)

Reliance on per capita waste generation Reliance on per capita waste generation estimates for developing countriesestimates for developing countries•• Per capita estimates derived from limited (urbanized) Per capita estimates derived from limited (urbanized)

areas with waste collection dataareas with waste collection data•• Does not account for effect of affluence on waste Does not account for effect of affluence on waste

disposal ratesdisposal rates

1313

11stst Order Decay Method (Tier 2) Order Decay Method (Tier 2) –– e.g. LandGEMe.g. LandGEM

QQM M = landfill biogas generation rate (m= landfill biogas generation rate (m33/yr);/yr);nn∑∑ = sum from opening year (i=1) through year= sum from opening year (i=1) through year

i=1i=1 of projection (n);of projection (n);kk = methane decay rate constant (1/yr);= methane decay rate constant (1/yr);Lo = ultimate methane generation potential (mLo = ultimate methane generation potential (m33/Mg);/Mg);MMii =mass of solid waste disposed in the =mass of solid waste disposed in the iithth year (Mg);year (Mg);ttii = age of the waste disposed in the = age of the waste disposed in the iithth year (years).year (years).

Note: Equation for calculation in 1 year increments shown; latesNote: Equation for calculation in 1 year increments shown; latest t version (LandGEM v. 3.02) uses 0.1 year increments.version (LandGEM v. 3.02) uses 0.1 year increments.

nn

QQMM = = ∑∑ 2 k Lo M2 k Lo Mii (e(e--ktktii))i=1i=1

1414

More on 1More on 1stst Order Decay Order Decay MethodMethod

Also approved by IPCCAlso approved by IPCCEstimates landfill methane generation x 2Estimates landfill methane generation x 2Need to apply estimates of % recovery and Need to apply estimates of % recovery and oxidation (e.g., IPCC values)oxidation (e.g., IPCC values)Commonly used in developing countries for Commonly used in developing countries for individual landfillsindividual landfills•• Required for regulatory compliance Required for regulatory compliance –– conservative conservative

estimates of landfill biogas emissionsestimates of landfill biogas emissions•• Useful for evaluating methane recovery project Useful for evaluating methane recovery project

requirementsrequirements

1515

Advantages of 1Advantages of 1stst Order Order Decay MethodDecay Method

Accounts for methane generation from Accounts for methane generation from historic waste disposalhistoric waste disposalAccounts for waste composition and Accounts for waste composition and moisture effects on waste decay ratesmoisture effects on waste decay ratesSiteSite--specific landfill biogas recovery specific landfill biogas recovery models have been validated with flow models have been validated with flow datadata

1616

Disadvantages of 1Disadvantages of 1stst Order Order Decay MethodDecay Method

Problems: Problems: historicalhistorical waste disposal estimateswaste disposal estimates•• Greater data requirements magnify problem of Greater data requirements magnify problem of

scarce, poor quality data scarce, poor quality data •• Uncertainty assigning single set of model parameters Uncertainty assigning single set of model parameters

for entire countryfor entire country•• Decay rates vary significantly with climate and waste Decay rates vary significantly with climate and waste

composition differencescomposition differences•• Inexperienced modelers rely on USEPA regulatory Inexperienced modelers rely on USEPA regulatory

default valuesdefault valuesResults in high estimates for developed countriesResults in high estimates for developed countriesInappropriate for developing countriesInappropriate for developing countries

1717

Summary of MethodologiesSummary of Methodologies

11stst Order decay (Tier 2) method most Order decay (Tier 2) method most accurate but not practical yetaccurate but not practical yetIPCC Tier 1 method more practical for global IPCC Tier 1 method more practical for global estimates, but accuracy can be improvedestimates, but accuracy can be improvedAlternative: Tier 1 IPCC method modified Alternative: Tier 1 IPCC method modified per per BognerBogner and Mathews, 2003*and Mathews, 2003*

**BognerBogner, J., and E. Matthews, Global methane emissions from landfills: , J., and E. Matthews, Global methane emissions from landfills: New New methodology and annual estimates 1980methodology and annual estimates 1980--1996, 1996, Global Global BiogeochemBiogeochem. . Cycles, 17(2), 2003. Cycles, 17(2), 2003.

1818

Proposed Revisions to IPCC Proposed Revisions to IPCC MethodologyMethodology

Use per capita annual energy consumption as a Use per capita annual energy consumption as a surrogate for per capita waste generationsurrogate for per capita waste generation•• Relationship of energy consumption to waste Relationship of energy consumption to waste

generation found through linear regressiongeneration found through linear regression•• Accounts for effects of both population and affluence Accounts for effects of both population and affluence

on waste generationon waste generationUse total population for developed countries; Use total population for developed countries; urban population for developing countries urban population for developing countries (where rural waste typically is not (where rural waste typically is not landfilledlandfilled))Use revised estimates of degradable organic Use revised estimates of degradable organic carbon dissimilated (carbon dissimilated (DOCDOCff), methane recovery, ), methane recovery, and oxidationand oxidation

1919

Basis for Revised Value for Basis for Revised Value for DOCDOCff

Degradable Organic Carbon Dissimilated Degradable Organic Carbon Dissimilated ((DOCDOCff) ) –– Use 0.5 instead of 0.77Use 0.5 instead of 0.77•• 0.77 from original IPCC method based on optimized 0.77 from original IPCC method based on optimized

low solids anaerobic digestion is too high for nonlow solids anaerobic digestion is too high for non--optimized high solids waste in landfillsoptimized high solids waste in landfills

•• 0.5 recommended by IEA/OECD/IPCC expert group 0.5 recommended by IEA/OECD/IPCC expert group meeting, Argonne National Laboratory, 1996meeting, Argonne National Laboratory, 1996

•• Laboratory studies indicate Laboratory studies indicate DOCDOCff of 0.25of 0.25--0.5 for 0.5 for optimized landfills; lower for nonoptimized landfills; lower for non--optimizedoptimized

2020

Basis for Revised Values for Basis for Revised Values for Methane Recovery (R)Methane Recovery (R)

R: Use updated methane recovery values extrapolated R: Use updated methane recovery values extrapolated from database of commercial projects (beneficial use)from database of commercial projects (beneficial use)•• Approximately 50Approximately 50--100% underestimate for many countries 100% underestimate for many countries

because flared methane excludedbecause flared methane excluded

2121

Basis for Revised Values for Basis for Revised Values for Methane Oxidation (OX)Methane Oxidation (OX)

OX: Use 0.1 for methane OX: Use 0.1 for methane oxidationoxidation•• Based on field study in Based on field study in

New Hampshire, USANew Hampshire, USA•• Field studies found OX Field studies found OX

values ranged from 0 to values ranged from 0 to >100%>100%

OX maximized at sites with OX maximized at sites with engineered gas recovery engineered gas recovery systems and thick, compostsystems and thick, compost--amended soil coversamended soil covers

2222

Compost Compost BiocoversBiocoversSimple to construct, local equipment and Simple to construct, local equipment and materialsmaterialsSignificant use of lowSignificant use of low--grade (or better) compost grade (or better) compost products derived from waste sourcesproducts derived from waste sourcesMethane emissions reduced vs. traditional Methane emissions reduced vs. traditional methodsmethodsUse of cover soils is reducedUse of cover soils is reducedTrial demonstrations already inTrial demonstrations already in--place in USA place in USA and Europeand Europe

2323

2424

CrossCross--section of section of BiocoverBiocover

2525

2626

2727

Results: Global Landfill Methane Results: Global Landfill Methane Emissions Estimates (Emissions Estimates (TgTg/year)/year)

YearYear 19861986 19961996Projected Projected

2006200620062006

Projection BasisProjection BasisGross Gross

EmissionsEmissions 18.018.0 20.720.7 21.321.317 17 TgTg net emissions net emissions and 20% recoveryand 20% recovery

Percent Percent RecoveryRecovery 2.4%2.4% 18.2%18.2% 20%20%

Assumes 10% Assumes 10% increase from 1996increase from 1996

Global Global RecoveryRecovery 0.40.4 3.83.8 4.34.3

Net Net EmissionsEmissions 17.617.6 16.916.9 17.017.0

USEPA* 1995USEPA* 1995--2005 2005 est. increase = 0.6%est. increase = 0.6%

*USEPA, December 2005, “Global Anthropogenic Non-CO2 Greenhouse Gas Emissions: 1990-2020,” Draft Report.

2828

ConclusionsConclusionsTotal global landfill methane emissions in 2006 Total global landfill methane emissions in 2006 = ~16.9 = ~16.9 TgTg = = 355 million tonnes CO355 million tonnes CO22eeAccuracy of estimates limited by lack of data, Accuracy of estimates limited by lack of data, particularly in developing countriesparticularly in developing countriesLarge increases in emissions from developing Large increases in emissions from developing countries could cause sharp increase in future countries could cause sharp increase in future global emissionsglobal emissionsMethane recovery and oxidation estimates are Methane recovery and oxidation estimates are conservative conservative –– large potential for emissions large potential for emissions reductions at landfills with methane recovery reductions at landfills with methane recovery and good soil coversand good soil covers

2929

THANK YOU!THANK YOU!