1. PERSPECTIVES ON LANDFILL GAS CAPTURE EFFICIENCY Frank R. Caponi CIWMB – Climate Change Workshop May 8, 2007 WASTEWATER RECLAMATION SOLID WASTE MANAGEMENT

2. WHAT IS LANDFILL GAS 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

3. COMMON SENSE APPROACH to Estimating Surface Emissions

11. COMMON SENSE APPROACH (verified through compliance monitoring)

12. COMMON SENSE APPROACH Summary 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

13. COLLECTON EFFICENCY Generation 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

14. COLLECTON EFFICENCY Generation Modeling Approach

16. Excel File that could be easy to operate

17. COLLECTON EFFICENCY Generation Modeling Approach

19. MODEL PREDICTION

20. COLLECTON EFFICENCY Generation Modeling Approach

22. COLLECTION EFFICIENCY ESTIMATES 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)

23. Flux Chamber Measurement of Surface Emissions

24. TOC as CH 4 Distribution Percent of 4 second readings > 4 ppm

25. CAPTURE EFFICIENCY Small Uncontrolled Sites ARB Early Action Measure These 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

26. SUMMARY 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

27. Contact me with any Questions: fcaponi@lacsd.org