Influence of biochar addition on methane metabolism during thermophilic phase of composting

CH4 is known to be generated during the most active phase of composting, even in well‐managed composting piles. In this manuscript, we studied the influence of biochar on the CH4 metabolism during composting of cattle manure and local organic wastes. We evaluated the presence of methanogens and methanotrophs in the composting piles quantified by the level of mcrA encoding methyl coenzyme M reductase alpha subunit and pmoA encoding particulate methane monooxygenase. A decrease of methanogens (mcrA) and an increase of methanotrophs (pmoA) were measured in the composting mixture containing biochar during the most active phase of composting. During the thermophilic phase, the mcrA/pmoA ratios obtained in the composting piles with biochar were twofold lower than in the pile without biochar.