Methane Dynamics in Landfill Vegetated Covers: Steady-State Model for Oxidation and Diffusion

Abstract

Recent advancements in landfill designs integrate vegetated covers as a sustainable layer to mitigate methane emissions. In this study, we developed a comprehensive analytical model incorporating diffusion, advection, oxidation, and root effects on methane and oxygen transport through landfill green covers. Root characteristics, including architecture, gas conductivity, depth, and density, were found to be influential parameters on methane oxidation and emission in vegetated covers. For example, at 0.4-m root depth, exponential versus uniform root distribution yields a 0.1221 difference in methane concentration for a root density of 105 m/m3. Roots with 3×10−5 m air/m root gas conductivity achieved 13.3% methane oxidation efficiency. Increasing root depth and density extended the aerobic zone, but CH4 oxidation efficiency declined beyond the root density of 104 m/m3. We showed that vegetation cover elevates methane emission control, potentially meeting emission standards [e.g., carbon farming initiative (CFI)] with root densities exceeding 104 m/m3. The balance between atmospheric oxygen and soil methane affects oxidation, with higher air transport (λ=3×10−4 m air/m root) resulting in 1.8% less methane oxidized. Overall, root–methane dynamics analysis should be optimized for efficient methane mitigation and control through landfill green cover systems.