Surface electron-polarized biochar-enhanced anaerobic digestion mechanism revealed by metagenomic binning strategy

Inefficient electron transfer is a key bottleneck for anaerobic digestion (AD), which often leads to system instability. Here, we propose for the first time a new strategy to solve the problem by adding surface electronpolarized biochar to enhance methanogenesis by providing electrons to methanogens through surface electron-poor/rich regions. Pyrolysis conversion of pigeon manure to conductive materials (CM) containing electron-poor/rich regions is realized. Different levels of CM (2.5, 5 and 7.5 g/L) are used to enhance methane production from pig manure and rice straw co-digestion systems. It is found that the addition of 5 g/L CM results in the highest cumulative CH4 production (187.4 +/- 8.0 mL/g VS (substrate)), 35.4% higher (P < 0.05) than the control (0 g/L). Methanogenic archaea are enriched. Synergistic metabolic mechanisms between the functional microorganism bin.CM52.160 (cellulose degradation) and bin.CM03.101 (methane production) are revealed by the metagenomic binning strategy. A large number of potentially unculturable electroactive microorganisms have been identified. This work provides important insights into the construction of micro-electric fields on material surfaces and offers a practical approach to improving AD performance.

Automated summary

In this study, a new strategy to improve anaerobic digestion (AD) efficiency by adding surface electronpolarized biochar was proposed. The addition of conductive materials (CM) containing electron-poor/rich regions enhanced methane production from pig manure and rice straw co-digestion systems. Metagenomic binning strategy revealed the synergistic metabolic mechanisms between cellulose degradation and methane production. The identification of potentially unculturable electroactive microorganisms provides important insights into improving the AD performance.