Quantification of parameters influencing methane generation due to biodegradation of municipal solid waste in landfills and laboratory experiments

The energy conversion potential of municipal solid waste (MSW) disposed of in landfills remains largely untapped because of the slow and variable rate of biogas generation, delayed and inefficient biogas collection, leakage of biogas, and landfill practices and infrastructure that are not geared toward energy recovery. A database consisting of methane (CH₄) generation data, the major constituent of biogas, from 49 laboratory experiments and field monitoring data from 57 landfills was developed. Three CH₄ generation parameters, i.e., waste decay rate (k), CH₄ generation potential (L₀), and time until maximum CH₄ generation rate (t_max), were calculated for each dataset using U.S. EPA's Landfill Gas Emission Model (LandGEM). Factors influencing the derived parameters in laboratory experiments and landfills were investigated using multi-linear regression analysis. Total weight of waste (W) was correlated with biodegradation conditions through a ranked classification scheme. k increased with increasing percentage of readily biodegradable waste (B_{r 0} (%)) and waste temperature, and reduced with increasing W, an indicator of less favorable biodegradation conditions. The values of k obtained in the laboratory were commonly significantly higher than those in landfills and those recommended by LandGEM. The mean value of L₀ was 98 and 88 L CH₄/kg waste for laboratory and field studies, respectively, but was significantly affected by waste composition with ranges from 10 to 300 L CH₄/kg. t_max increased with increasing percentage of biodegradable waste (B₀) and W. The values of t_max in landfills were higher than those in laboratory experiments or those based on LandGEM's recommended parameters. Enhancing biodegradation conditions in landfill cells has a greater impact on improving k and t_max than increasing B₀. Optimizing the B₀ and B_{r 0} values of landfilled waste increases L₀ and reduces t_max.