Mitigating Methane Emissions From Landfill By Biocover

Lanfills are main sources due to anthropogenic activites, account for about 18% of total global CH4 emissions reported by Intergovernmental Panel on Climate Change (IPCC). Because of its strong global warming potential, CH4 changes global climates and reduces tropospheric oxidation capacity by reacting with hydroxyl radicals. Ozone (O3) is generated in troposphere associated with reaction, which theatens and destroies the agriculture and ecosystem, for instance, growth of O3 in troposphere increases premature mortalities. Reduction of CH4 emissions from landfills can accelerate the balance between CH4 sources and sinks, and contribute to soil carbon and nitrogen clycles. Yard wastes usually consist of soil, gravels, leaves, grass and shards of glass etc., being filled into landfills may increase the pressure on landfill volume, being reclassified cause higher cost, being composted may not match the requirements of compost quantity. Generally, yard wastes are riched in organic matter and nutrients such as N, P and K, which may be suitable to be material for biocover construction because composts or mixture of composts, woodchips and soil obtain better methane oxidation performance compared to traditional clay:specific surface area of organic matter riched material is usually high, that is essential for microbial growth, and more initial populations could reduce the lag effect of microbial oxidation. Another point is high organic matter improve water holding capacity and heat conductivity of material, which may resist the impact of temperature fluctuation on material and decrease the risk of CH4 leakage due to dehydration of clay.Main subjects of this study are:1) The mechanism of methane oxidation and the design and construction of biocover.2) Measurements of biocover composition, air and water permeability, diffusion coefficient, retention curve etc., stability tests, incubation and measurements of microbial parameters of biocover3) Performance of methane oxidation in field was measured through multiple methods such as sulfur hexafluoride (SF6) tracer, C13 isotope and static chamber.4) Presenting a carbon balance method to calculate methane oxidation and perform sensitivity analysis when respiration of non-methanotrophic bacteria and production of CO2 and CH4 due to degradation of organic matter.5) Quantifying the variation of methane oxidation with seasonal change and two models were utilized to predict the response to variation of temperature and moisture content.6) Distribution of gas flux in biocover was measured and a 3D simulation was performed to investigate the influence of biocover properties in gas transport.Results suggest that yard wastes can be alternative material for biocover to mitigate methane emissions from landfill. The performance varies associated with temperature and moisture content due to seasonal variation.Models combined effect of temperature and moisture content can predict the variation of oxidation performance in biocover with 24-month matured material, which is relatively low in organic matter. Distribution of gas fluxes also exhibits spatial variability, which is related to distribution of moisture content and dry bulk density. In addition to this, significant amount of methane generation was observed in both biocovers, which could be cut down through thinning biocover without reduction reduction of methane oxidation.