EVALUATION OF THE SEASONAL VARIATION OF THE METHANE MASS BALANCE AT A FRENCH LANDFILL

摘要

One tonne of landfilled solid waste can potentially produce 120-150 m~3 of landfill gas within several years. Without any recovery system, landfill gas can migrate through landfill cover soils toward the atmosphere and contribute to the greenhouse effect. But a well designed collection system associated with the presence of aerobic methanotrophic microorganisms in cover soils can significantly reduce these methane emissions. In order to study the methane recovery and oxidation rates and net emissions to the atmosphere in landfill settings, a research program has been performed by the Environment, Energy and Waste Research Center (Vivendi Environment group) with the financial support of the French Environmental Protection Agency (ADEME). It aims at identifying and quantifying the potential pathways of methane from the landfill. A first evaluation of the methane mass balance has been made on a French landfill (Diot et al, 2001a.). This field campaign, completed during winter conditions, showed that the gas recovery system drastically reduced net emissions of methane to the atmosphere. 94% of the biogas produced was recovered, net emissions were about 1,8 % of the biogaz produced and oxidation was negligible. These results are mainly influenced by parameters such as the soil water content, the temperature and the atmospheric pressure. A second field campaign was completed on the same site in summer conditions―early September 2001 in order to compare the rate of methane recovered, emitted or oxidized.