Improved Methane Estimations from Landfills Using a Multicomponent Multiphase Methane Generation Model Based on Three-Phase Degradation Kinetics

Landfills significantly contribute to global methane (CH4) emissions, a potent greenhouse gas. Accurate CH4 estimation is crucial for optimizing landfill gas recovery and mitigating reductions. This study presents a novel approach for improved CH4 generation estimation by accounting for the distinct degradation behaviors of different municipal solid waste (MSW) components. The approach segments the CH4 generation curve into three phases: the fast-rising phase (FRP), fast-declining phase (FDP), and slow-declining phase (SDP). Biochemical methane potential (L0) and decay rates (k) are determined for each phase across four key MSW components: food waste, paper waste, textile waste, and yard waste. Phase-specific decay rates (k1 for the FRP, k2 for the FDP, and k3 for the SDP) are derived from separate decay equations fitted to each phase. Notably, the SDP consistently exhibits the lowest decay rate for all components. The developed multicomponent multiphase methane generation model (MCMP-MGM) incorporates these phase-specific k values and component-specific L0 values to estimate landfill CH4 generation. The MCMP-MGM achieves significantly higher accuracy than previous studies, which were based on a single k and L0. The errors in the predicted CH4 generation and field measurements range between 7% and 27% across three landfill sites in the present study. Additionally, the impact of changes in waste composition and volume driven by waste diversion schemes is assessed. A 41.5% reduction in total waste results in a 49% decrease in methane generation, while a 78.9% reduction leads to a 93% decrease, emphasizing the importance of component-specific decay rates for CH4 estimation. Therefore, estimation of methane generation potential from landfills should be done carefully to account for different waste components in MSW. The accurate estimation of methane generation from landfills helps landfill managers and planners effectively mitigate the greenhouse gas emissions generated from landfills.