Methane removal efficiency in biochar-methanotroph-clay landfill cover

The landfill is one of the main sources of methane emissions. The landfill cover is at the top of a landfill as an important solution to reduce methane release. However, the gas closure capability of the conventional landfill cover is so poor that results in prolonged issue of uncontrolled, low-intensity methane emissions and exacerbates the greenhouse effects. In this study, the biochar and methanotroph amendment to clay are proposed to create an eco-friendly landfill cover, biochar-methanotroph-clay (BMC) cover. It is designed to combine the absorbing or oxidizing methane capabilities of biochar and methanotroph, aiming for more economical, sustainable and effective methane removal approach. By adopting chemical oxidation aging method, water film transfer method and other methods, a total of 48 groups of experiments are conducted to stimulate the effects of biochar content, oxidation aging times and methane-filled days to the methane removal efficiency of the BMC. The results indicate that the methane removal efficiency increases first and then decreases with the increase of the biochar content. It increases gradually with the increase of the oxidation aging times and methane-filled days. After 6 times of oxidation aging and 30 days of breeding methanotroph, the BMC with the biochar content of 5% shows the highest methane removal capacity amounting to 14.05 mg/g, which is more than twice the number of the clay. These results are expected to offer insights for the design, construction and maintenance of the BMC landfill cover system.