Dual roles in interspecies electron transfer of carbon-based materials for accelerating anaerobic digestion of food waste

Food waste is tremendously generated and leads to serious environmental pollution if it is improperly disposed. Anaerobic digestion is recognized as an effective biotechnology to treat food waste. In order to improve the conversion efficiency, the effect of carbon -based materials on anaerobic digestion of food waste was investigated, and the microbial communities and electron transport pathways were also analyzed. The results showed that adding biochar improved the performance of anaerobic digestion of food waste, but adding graphite had no significant effect. The maximum daily methane yield of 67.79 +/- 6.37 and 72.78 +/- 6.17 mL/g VS center dot d were obtained with 1.250 (BC10) and 1.875 (BC15) g biochar/g VS raw material added, increased by 13.27% and 21.61% in comparison with the control system. Meanwhile, the systems reached 80% of cumulative methane yield on day 10, and the increase of 13.50% (423.66 +/- 13.74 mL/g VS) and 13.57% (423.96 +/- 20.33 mL/g VS) were obtained for the methane yield. Adding biochar selectively increased the relative abundance of Syntrophomonas, Clostridium sensu stricto, Petrimonas, Clostridium XlVb, Comamonas, Acinetobacter, Methanothrix and Methanobacterium. The interaction between Methanobacterium and Syntrophomonas was also promoted due to biochar acted as an electron carrier. Therefore, biochar had complex regulation on electron transport pathway of anaerobic digestion and promoted the conversion efficiency of food waste.