Time-Depedent Methane Generation from Municipal Solid Waste in Landfills with Different Moisture Contents and Overburden Stresses

Time-dependent methane (CH₄) generation during biodegradation of municipal solid waste (MSW) in landfills is critical to the design of biogas collection and energy recovery systems. Uncollected CH₄ migrates to the environment and is considered anthropogenic greenhouse gas emission. Therefore, CH₄ generation in landfills is of great interest to environmental engineers and scientists alike. CH₄ generation from MSW concurs with other biochemical, mechanical and hydrological processes in landfills. These processes are coupled and their interactions have not been elucidated clearly. Some of the major factors influencing CH₄ generation are initial waste composition, moisture content (w_c), and overburden stress (σ_v). In this study, the author synthesizes and analyzes the results of more than 20 laboratory large-scale MSW biodegradation experiments available in the literature, among which some experiments were conducted by the authors. Specifically, each time-dependent CH₄ generation curve is characterized by four parameters, CH₄ generation potential (L₀), maximum CH₄ generation rate (r_CH4,max), lag time before the initiation of CH₄ generation (t_rCH4,0), and lag time before achieving r_CH4,max (t_rCH4,max). Major findings of the data analysis are: 1) initial waste composition is influential to L₀ and r_CH4,max; 2) r_CH4,max increases with increasing L₀ and both are influenced by w_c; 3) t_rCH4,0 and t_rCH4,max are correlated and both influenced by w_c; and 4) σ_v plays a secondary role in CH₄ generation, although it affects significantly mechanical and hydrological processes of MSW in landfills.