Response of methane oxidation biosystems to controlled ingress of oxygen

Methane (CH₄) emissions from landfills significantly contribute to global warming, requiring effective mitigation strategies. Methane oxidation biosystems (MOB) use methanotrophic bacteria to convert CH₄ into carbon dioxide (CO₂), offering a cost-effective and sustainable solution. Optimizing MOB performance depends, among other parameters, on adequate oxygen (O₂) supply. This study examines the impact of the O₂/CH₄ ratio on methane oxidation efficiency using a compost-wood chip mixture as the oxidation medium. Six experimental conditions were tested, maintaining an empty bed residence time (EBRT) of 90 min, except for one case where the EBRT was 8880 min. Results show that a 3:1 ratio leads to the optimal removal efficiency (99.5%). Microbiological analysis and respiration tests indicate that heterotrophic respiration and organic matter degradation consume O₂, requiring additional oxygen beyond the stoichiometric demand of 2 for methane oxidation. When O₂ availability relied on diffusion, the efficiency dropped by 30%, underscoring the importance of optimizing O₂ delivery mechanisms. These findings highlight the necessity of a precise O₂/CH₄ ratio control to enhance MOB performance, enabling the reduction of EBRT while maintaining biofilter size or decreasing system size without compromising efficiency.