Effects of Hydrophobic Biochar-Modified Landfill Soil Cover on Methane Oxidation

Landfill cover soils play an important role in mitigating landfill methane (CH₄) emissions. Incorporating biochar into the soil has proven effective in reducing CH₄ emissions. However, the role of hydrophobic biochar in this context remains underexplored. This study investigated the CH₄ removal efficiency of a biochar-modified landfill soil cover column (RB) and hydrophobic biochar-modified landfill soil cover column (RH) under varying CH₄ influx gas concentrations (25 and 35%), simulated CH₄ inflow rates (10, 15, and 20 ml/min), and temperatures (20, 25, 30, 35, and 40 °C). RH consistently outperformed RB in terms of CH₄ removal efficiency under these experimental conditions. The optimal conditions for CH₄ degradation by both RB and RH were observed at a CH₄ influx gas concentration of 35%, a simulated CH₄ inflow rate of 10 ml/min, and a temperature of ~30 °C. RH achieved a CH₄ removal rate of up to 99.96%. In summary, the addition of hydrophobic biochar enhanced the air permeability and hydrophobicity of landfill cover soils, providing a promising alternative to conventional cover soils for reducing CH₄ emissions from landfills.