Enhancing anaerobic methane oxidation in landfill cover soils with leachate recirculation

Enhancing anaerobic oxidation of methane (AOM) in landfill cover soils represents a cost-effective strategy for mitigating methane emissions. Recirculating leachate provides diverse electron acceptors that support AOM, but the effects vary across landfills. Here, we conducted anaerobic incubations of cover soil with 10 different leachates and stable isotope labeling to examine their impact on AOM. Results showed significant variability in AOM rates (over 60 %), influenced by ammonia nitrogen (NH₄⁺-N), nitrite nitrogen (NO₂⁻-N), and total organic carbon (TOC). AOM was reduced by 24 % and 37 % at 5000 mg/L NH₄⁺-N and 1000 mg/L TOC, respectively, while it increased by 30 % when NO₂⁻-N was below 100 mg/L. The structural equation model demonstrated that TOC and NH₄⁺-N directly and indirectly suppressed AOM by suppressing Methylobacter, while NO₂⁻-N promoted AOM by stimulating Methylobacter. This work proposes a strategy for simultaneous leachate disposal and carbon mitigation.