PERSPECTIVES ON PERSPECTIVES ON LANDFILL GAS CAPTURE LANDFILL GAS CAPTURE
EFFICIENCYEFFICIENCY
Frank R. CaponiCIWMB – Climate Change Workshop
May 8, 2007WASTEWATER RECLAMATION
SOLID WASTE MANAGEMENT
WHAT IS LANDFILL GAS WHAT IS LANDFILL GAS CAPTURE EFFICIENCY?CAPTURE EFFICIENCY? Difficult to determine! Typical method:
Efficiency = Collection/Generation Gas collected = Measured Gas generated = Theoretical Model Gas surface emissions = Typically calculated Most estimation techniques incorrect!?? Ignores cover methane oxidation
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACHto Estimating Surface Emissionsto Estimating Surface Emissions
COMMON SENSE APPROACHCOMMON SENSE APPROACH(verified through compliance monitoring)(verified through compliance monitoring)
COMMON SENSE APPROACHCOMMON SENSE APPROACHSummarySummary
Thriving vegetation indication of a well-controlled landfill– (we think >90 to 95% collection efficiency)
Surface concentration measurements of methane often at or near background– Regulations such as Federal NSPS or SCAQMD Rule
1150.1 require routine monitoring
Dead vegetation = composting– Air intrusion by to much vacuum– Federal NSPS limits oxygen at wells
COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach Models developed by EPA or proprietary
variation Models developed as a compliance tool or
for state inventory development During development, EPA warned of
inaccuracies– Overpredicts by 40% to 2-3X
Consultants use to predict gas generation for energy projects
Often misused to calculate collection efficiency
COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach
Excel File that could be easy to
operate
COLLECTON EFFICENCYCOLLECTON EFFICENCYGeneration Modeling ApproachGeneration Modeling Approach
MODEL PREDICTION
COLLECTION EFFICIENCY COLLECTION EFFICIENCY ESTIMATESESTIMATES
EPA uses 75% default– No basis
Some groups say 50% or less based on life cycle– Not applicable here- 94% waste in place
controlled Bogner field studies (flux chambers) show
85% or greater in Europe LACSD hybrid theoretical/measured show
95%+ Recent LACSD field study (flux chamber)
shows 100% (DTSC approved methods)
TOC as CHTOC as CH44 Distribution Distribution
Percent of 4 second readings > 4 ppmPercent of 4 second readings > 4 ppm
CAPTURE EFFICIENCYCAPTURE EFFICIENCYSmall Uncontrolled SitesSmall Uncontrolled Sites
ARB Early Action MeasureThese sites likely low quality methane– Sites may be older– Sites likely to be partially aerobic
Attempts to capture methane counterproductive– Placing site under vacuum will draw in more air– More air = less methane and composting– Managing low quality methane gas may need
supplemental fuel, such as natural gas to flare = more emissions of criteria pollutants
SUMMARYSUMMARY Landfills with Collection Systems well controlled Practical evidence such as healthy vegetation Theoretical models faulty – poor method of
estimating collection efficiency Field methods and hybrid methods more reliable
and accurate Data indicates collection efficiency 85% to 100%;
>95% likely Collecting landfill gas from small sites
counterproductive