Methane production from municipal refuse: A review of enhancement techniques and microbial dynamics

Methane is recovered from about 100 municipal solid waste landfills in the U.S. in saleable volumes, although yields are 1 to 50% of the methane potential of refuse based on biodegradability data. Studies on the microbiology of refuse decomposition and efforts to enhance refuse methanogenesis are reviewed here. Results of studies on the effects of leachate recycle and neutralization, a reduction in refuse particle size, the addition of anaerobic sewage sludge or old refuse as a seed, nutrient addition, calcium carbonate addition, and moisture on methane production are examined in consideration of new findings on landfill microbiology. A four‐phase description of refuse decomposition with leachate recycle, including an aerobic phase, an anaerobic acid phase, an accelerated methane production phase, and a decelerated methane production phase, is proposed. Mass balances and pumping tests may be used to estimate the methane potential of a sanitary landfill. The use of empirical, zero, and first‐order models to project methane production is reviewed.