Enhancement effect of biochar addition on anaerobic co-digestion of pig manure and corn straw under biogas slurry circulation

Based on the semi-continuous anaerobic co-digestion (AcoD) reactor, the effects of biochar addition on the in-ternal environmental changes and gas production characteristics were studied under the condition of biogas slurry recirculation. The results showed that the addition of biochar enhanced the degradation and metabolic pathways of acetate and propionate, thereby reducing the concentrations of volatile fatty acids (VFAs), total ammonia and chemical oxygen demand by 55 %, 41 % and 61 %, respectively. The buffer system formed by the combination of NH4+ and VFAs of C2-C5 was also enhanced, thereby improving the stability of the system. The addition of biochar effectively increased the relative abundance of Bacteroidetes, Chloroflexi, Spirochaetota and Synergistota, and enhanced three methanogenic metabolic pathways. This study provides scientific support for the application of biochar to solve the system inhibition in mixed substrate semi-continuous AcoD process and provides technical support for the stable operation of biogas project.

Automated summary

This study investigated the effects of biochar addition on internal environmental changes and gas production characteristics in a semi-continuous anaerobic co-digestion (AcoD) reactor with biogas slurry recirculation. The results showed that biochar addition enhanced the degradation and metabolic pathways of acetate and propionate, resulting in decreased concentrations of volatile fatty acids, total ammonia, and chemical oxygen demand. The addition of biochar also improved the stability of the system and increased the abundance of certain bacterial groups and methanogenic pathways. This study provides scientific and technical support for the application of biochar in improving the stability of biogas projects.