Concurrent aerobic methane oxidation and biodegradation of waste in shallow layer of landfill during aeration

Aeration is a common remediation technique to mitigate greenhouse gas emissions and accelerate waste biodegradation in landfills. However, designing of landfill aeration remains challenging. Enhancing the understanding of concurrent methane (CH₄) oxidation and aerobic biodegradation of waste during landfill aeration is crucial. This study combined laboratory experiments with simplified modeling to elucidate these two processes occurring in waste after different biodegradation periods. As biodegradation period of waste increased, the CH₄ consumption rates decreased, suggesting a gradual change in microbial community. The oxygen (O₂) consumption rates initially increased and then decreased in three reactors with the different concentrations of CH₄ at the beginning of the reaction (initial CH₄ concentration) of 20 %, 17 %, and 10 %. The peak O₂ consumption rates were -0.048, -0.063, and -0.072 mol day^-1 kg^-1 dry mass, respectively. A simplified model was developed based on the chemical reaction equations, balance equations, and elemental analysis of degradable waste to quantify the molar fractions of O₂ consumption attributed to CH₄ oxidation and aerobic waste biodegradation. The molar fraction of O₂ consumption by CH₄ oxidation ranged from 1 % to 88 %. The CH₄ removal efficiency ranged from 4 % to 16 %, which was influenced by the competing aerobic waste biodegradation and was lower than values reported in studies using compost materials, such as garden waste or natural soil as substrates. Nevertheless, CH₄ oxidation in shallow layers of landfill contributes to overall CH₄ oxidation globally. This study provides a valuable dataset and theoretical support for optimizing aeration design and mitigating CH₄ emissions from landfills.