The effects of initial substrate concentration, C/N ratio, and temperature on solid-state anaerobic digestion from composting rice straw

• Solid-state anaerobic digestion from composting rice straw was studied.
• Microbial community was determined by the high-throughput sequencing technique.
• The optimal condition for biogasifcation is 35.6 °C, 20% ISC and C/N of 29.6:1.
• Methanogen was shifted from Methanobacterium to Methanoculleus during the process.

This study investigated the possibilities of improving the biogasification from solid-state anaerobic digestion (SS-AD) of composting rice straw (RS) based on the optimized digestion temperature, initial substrate concentration (ISC) and C/N ratio. RS compounds, such as lignin, cellulose, and hemicellulose, were significantly degraded after composting. A significant interactive effect of temperature, ISC and C/N ratio was found on the biogasification of SS-AD of composting RS, and a maximum biogas production was achieved at 35.6 °C, with a 20% ISC and a C/N ratio of 29.6:1. The verification experiment confirmed the optimization results. High-throughput sequencing analysis indicated that microbial communities in the SS-AD mainly consist of Methanobacteria, Bacteroidia, Clostridia, Betaproteobacteria, and Gammaproteobacteria. A dominant Methanobacteria was shifted from Methanobacterium to Methanoculleus during the SS-AD process. This study provides novel information about the interdependent effects and microbial behavior of AD.