Effect of MSW properties on bio-thermo-hydro-mechanical responses in anaerobic landfills

Understanding the coupled bio-thermo-hydro-mechanical responses of municipal solid waste (MSW) in landfills is crucial for sustainable landfill design and proper risk management during its service life. The objective of this study is to investigate the impact of different MSW compositions, initial methane bacteria concentration, permeability characteristics, and external temperature on the coupled behaviours of MSW in landfills. A coupled comprehensive multi-phase, multi-components model and a corresponding solver were adopted to simulate long-term landfill behaviours. The results demonstrated that MSW with high-kitchen components led to severe biodegradation reactions and higher gas and leachate pressures in landfills, potentially increasing the risk of landfill instability. A high initial concentration of methane bacteria could significantly accelerate the MSW biodegradation, thereby increasing the gas production rate. In practical applications, leachate recirculation with high microbial activity could promote landfill stabilisation. High permeability coefficients could reduce internal liquid and gas pressures but may also diminish the extent of long-term biochemical reactions. A lower initial temperature had a more pronounced effect on the decline rate of methane bacteria, thereby inhibiting the decline rate and accelerating the methanation reaction in the early stages. These findings provide a valuable contribution to the understanding of long-term landfill behaviour and management.