Improved biogas production of dry anaerobic digestion of swine manure.

In this work, wrapped granular activated carbon (GAC) and acclimated sludge were employed to enhance the efficiency of the dry anaerobic digestion of swine manure in semi-continuous tests. The addition of wrapped GAC increased the volumetric biogas production rate by 10.6%, and the removal efficiencies of TS and VS were enhanced by 5.3% and 6.6%, respectively. The concentration of total volatile fatty acids (TVFA) was 30.3% lower in the GAC reactor, but the total ammonia nitrogen (TAN) content was 15.3% higher. Inoculating with acclimated sludge helped the system survive unfavorable conditions, where the TAN and TVFA contents were around 5,200 mg/L and 8,800 mg/L, respectively, but it failed to improve the biogas production efficiency. The mechanisms that allowed GAC to increase the production of biogas were related to the improved hydrolysis process, enhanced microbial adhesion, the provision of electronic bridges, and enrichment of functional microorganism.