Landfill Gas Collection Efficiency at One Municipal Solid Waste Landfill in Northern China

Collection efficiency is a key indicator for the design and evaluation of municipal solid waste (MSW) landfill gas (LFG) collection and utilization system. Although most Chinese sanitary landfills have been equipped with LFG collection systems, there are no accurate data on collection efficiencies, lack of which always result in huge loss of LFG or investment. The fates of methane generated in a landfill include collection through LFG pipes, fugitive emission from the surface, and oxidation by methanotrophs. Field campaigns for measuring methane emission and oxidation were conducted at one landfill located in Beijing. Methane samples were collected by means of static flux chambers. The measurements were carried out at soil covered road and operating and slope surfaces. Two methods, i.e. landGEM model based and field measurement based estimation were used for calculating the collection efficiency in this research. The methane emission amount were 262.1 and 53222.4 m3 in July 2013 for the working and slope surfaces, respectively. The collection efficiency was 94.3% according to field measurement. Calculated with the LandGEM model, the collection efficiencies for 2011 and 2012 were 48.5 and 47.7% (k=0.09 yr-1) and 20.9 and 22.2% (k=0.3 yr-1), respectively. The estimation based on field measurement was more credible than the other, although the lateral migration and the storage insitu were naglected. The model method did not perform well probably due to the inapplicability of the landGEM model on this landfill, where the MSW was packed into small-subcells, and inaccurate parameter, k.