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

Methane (CH) emissions from thermophilic composting (TC) are a substantial contributor to climate change. Hyperthermophilic composting (HTC) can influence CH-related microbial communities at temperatures up to 80 °C, and thus impact the CH emissions during composting. This work investigated CH emissions in sludge-derived HTC, and explored microbial community succession with quantitative PCR and high-throughput sequencing. Results demonstrated that HTC decreased CH emissions by 52.5% compared with TC. In HTC, the CH production potential and CH 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 × 10 to 0 g TS) in HTC, which was more significant than the reduction in pmoA (2.0 × 10 to 2.1 × 10 g TS), and thus lead to reduce CH 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 CH emissions in HTC. This work provides important insight into mitigating CH emissions in composting.