Effect and microbial reaction mechanism of rice straw biochar on pore methane production during mainstream large-scale aerobic composting in China

This study investigated the effect of rice straw biochar (RSB) on methane production during mainstream large-scale aerobic composting by using high-throughput sequencing and quantitative PCR. A 55-day large-scale aerobic composting experiment under cyclical forced-turning with aeration was conducted with control (a) and experimental groups (BC), namely, without and with 10% RSB. The methanogen/methanotroph and microbial community of samples were analyzed by mcrA/pmoA and 16S rRNA/internal transcribed spacer region, respectively. The pore methane concentration had a positive relationship with mcrA and mcrA/pmoA. RSB accelerated methane production, which was reflected by an increase in mcrA. The diversity of bacteria and fungi increased by addition of RSB. Addition of RSB contributed to increasing the RAs of Methanobrevibacter and Methylobacterium. Methanobrevibacter was related to CH4 production, and Methylobacterium related to CH4 consumption through the metabolism of methyl material. Thus, the biochar has always increased the diversity of bacteria, including Methanobrevibacter and Methylobacterium. The optimal way to control CH4 production is to reduce the number of mcrA/pmoA. Meanwhile, RSB contributed to methane production because of its small particle size in this study. The biochar particle size could be further optimized during large-scale aerobic composting process. (C) 2019 Elsevier Ltd. All rights reserved.