Microbial methane oxidation for the reduction of landfill gas emissions

With about 40 to 60 Mt of methane emitted each year worldwide, landfills are an important global source of this greenhouse gas. These emissions are especially caused by inadequate gas extraction facilities, missing gas collection systems at old dump sites and landfills or unauthorized open dumping. A low cost alternative method or an additional measure to the conventional degasification systems is the application of the natural potential of microbial methane oxidation in landfills in suitable cover layers. By creating optimal ambient conditions for methanotrophic bacteria in cover layers, it is possible to foster the microbial activity and to attain very high oxidation rates. The results derived from laboratory experiments as well as first experiences from a large-scale field investigation show that waste composts are suitable carrier substrates for methanotrophic bacteria. Methane oxidation rates in compost were clearly higher than in natural soils. Even at a methane supply of about 200 - 350 I CH4 m-2d-1 in the laboratory experiments all methane could be oxidized in the compost material.