Numerical simulation of water-gas multiphase flow in landfill soil covers

Effective landfill cover design is critical for methane capture in waste-to-energy conversion. This study developed a coupled water-gas numerical model to quantify methane transport mechanisms in unsaturated landfill soil covers. Validated against soil column experiments, the model accurately simulated gas pressure and multicomponent concentration profiles. Parametric analysis demonstrated that cover thickness and volumetric water content are pivotal governing factors for methane flux attenuation. Increased thickness and higher moisture content significantly enhanced the cover's gas-blocking capacity by reducing gas permeability. These findings provide quantitative guidance for strategically designing earthen covers to minimize fugitive methane emissions while maximizing recovery for energy generation.