Performance of Biocover Materials in Mitigating Methane Emissions from Landfills under Different Loading Rates

Biocovers are an innovative solution to reduce methane (CH4) emissions from landfills. This study investigates the performance of biocover materials, including food waste compost, yard waste compost, and peat moss, in mitigating methane emissions through laboratory column experiments that applied different CH4 loading rates. The biocovers studied were 500 mm thick and consisted of a 70∶30 ratio by mass of compost (or peat) to sand. While food and yard waste composts effectively supported CH4 oxidation, the peat biocover failed to provide appropriate conditions for CH4 oxidation over the study period. A numerical model was validated and used to understand the properties, processes affecting CH4 oxidation, and optimal design of the biocover materials. The results indicated that the maximum simulated removal efficiency of CH4 was 81.1%–84.4% in food waste compost and yard waste compost, respectively, at the lowest experimental loading rate of 142 g m−2 day−1. As expected for the experimental conditions tested, the CH4 removal efficiency decreased when the methane loading rate increased. The CH4 removal efficiency was greater than 96.6% when the simulated loading rate was less than 96 g m−2 day−1, which reflects reported CH4 emissions rates at small and older landfills. The results demonstrate that the methane oxidation capacity is limited by oxygen penetration depth and the gas saturation profile, which affected the CH4 residence time at different loading rates. Also, the simulated model results showed that increasing the thickness of the biocover layer (greater than 500 mm) does not increase the amount of CH4 oxidized even with increasing residence time, due to limitations on O2 ingress into the material. The study findings suggest that biocover materials such as yard and food waste compost materials have great potential for reducing CH4 emissions from landfills, especially older and smaller landfills.