Hyperthermophilic composting significantly decreases methane emissions: Insights into the microbial mechanism

Methane (CH4) emissions from thermophilic composting (TC) are a substantial contributor to climate change. Hyperthermophilic composting (HTC) can influence CH4-related microbial communities at temperatures up to 80 °C, and thus impact the CH4 emissions during composting. This work investigated CH4 emissions in sludge-derived HTC, and explored microbial community succession with quantitative PCR and high-throughput sequencing. Results demonstrated that HTC decreased CH4 emissions by 52.5% compared with TC. In HTC, the CH4 production potential and CH4 oxidation potential were nearly 40% and 64.1% lower than that of TC, respectively. There was a reduction in the quantity of mcrA (3.7 × 108 to 0 g−1 TS) in HTC, which was more significant than the reduction in pmoA (2.0 × 105 to 2.1 × 104 g−1 TS), and thus lead to reduce CH4 emissions. It was found that the abundance of most methanogens and methanotrophs was inhibited in the hyperthermal environment, with a decline in Methanosarcina, Methanosaeta and Methanobrevibacter potentially being responsible for reducing the CH4 emissions in HTC. This work provides important insight into mitigating CH4 emissions in composting.