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

[Display omitted] • Pigeon manure biochar with electron poor/rich regions on the surface. • Biochar (5 g/L) can significantly increase cumulative methane production. • Adding biochar facilitated the enrichment of methanogenic archaea. • Metagenomes reveal synergistic mechanisms between functional microbes. 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 electron-polarized 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 CH 4 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. [ABSTRACT FROM AUTHOR]