Mitigation of methane emissions in a pilot-scale biocover system at the av miljø landfill, denmark: system design and gas distribution

Greenhouse gas mitigation at landfills by methane oxidation in engineered biocover systems is believed to be a cost effective technology but so far a full quantitative evaluation of the efficiency of the technology in full scale has only been carried out in a few cases. A third generation semi-passive biocover system was constructed at the AV Miljø landfill. The biocover is fed by landfill gas pumped out of three leachate wells. An innovative gas distribution system was used to overcome the often observed overloaded hot spot areas resulting from uneven gas distribution to the active methane oxidation layer. Performed screening of methane and carbon dioxide concentration at the surface of the biocover showed homogenous distributions indicating an even gas distribution. This was supported by result from a performed tracer test where the compound HFC-134a was added to the gas inlet over a 12 day period. Studies of the tracer movement within the biocover system showed very even gas distribution in gas probes installed in the gas distribution layer. Also the flux of tracer out of the biocover surface as measured by flux chamber technique showed a spatially even distribution. The methane oxidation efficiency was studied in a follow on paper included in these proceedings.