Novel nitrogen-doped biochar supported magnetite promotes anaerobic digestion: Material characterization and metagenomic analysis.

Although different conductive materials have been applied to anaerobic digestion, there has not been a material that can really combine their merits and make up their shortcoming from each other. In this study, a novel nitrogen-doped biochar supported magnetite (FeO@N-BC) was synthesized. Various material characterizations confirmed that nitrogen atoms were successful doped into the biochar and magnetite precipitated on its surface. 5 g/L FeO@N-BC achieved the highest promotion of cumulative CH production by 1.75 times compared with the blank group. Further metagenomic analysis revealed that FeO@N-BC could increase the gene abundances of pilA, MmcA, Fpo, Rnf and HdrEd in bacteria Clotridium, Pseudomonas and Syntrophomonas and archaea Methanosarcina. Redundancy analysis showed that it was electrical conductivity and electron exchange capacity that were the key physicochemical characteristics for FeO@N-BC to facilitating direct interspecies electron transfer. This study provides a reference for future conductive material synthesis and its application for anaerobic digestion.