Exploring Effective Bio-Cover Materials for Mitigating Methane Emission at a Tropical Landfill

Methane emission and oxidation in different bio-cover materials, i.e., sandy loam, compost, and stabilized wastes, were investigated at a municipal solid waste landfill in Thailand. The bio-cover was purged with extracted landfill gas while methane reduction through biological oxidation was studied. The moisture content in bio-cover materials was maintained with natural rainwater during the wet period and leachate irrigation during the dry period. Methane emissions were found to vary between media and were influenced by rainfall. The methane loading rates of the bio-cover varied from 8.2-20.3 mol/m3/d, being higher during the dry period. Methane removal rates at the bottom part of the biofilter (0.4-0.6 m depth), the most active zone, were found to be from 6.4-10.9 and 7.8-11.4 mol/m(3)/d during wet and dry periods. The highest methane removals were found in the lower part of sandy loam, followed sequentially by compost and stabilized wastes. Nevertheless, compost had the highest methane oxidation capacities and greater methanotroph population compared to sandy loam and stabilized wastes. Methanotroph type I was found to predominate during the dry period, whereas methanotroph type II was predominant during the wet period.