Preparation of sludge-derived activated carbon and its enhancement of biogas production from long-chain fatty acid degradation

Adding activated carbon to the anaerobic digestion of food waste can effectively enhance degradation efficiency and biogas production. However, the cost of commercial activated carbon remains relatively high. But in this study, sludge from a wastewater treatment plant was used to prepare sludge-derived activated carbon (SDAC) by the molten salt method. The SDAC synthesized under a calcination temperature of 500 °C and a time of 2 h with a ZnCl2 to sludge mass ratio of 1 was used to improve stearic acid degradation. 0.3 g L−1 of stearic acid was completely degraded by the ninth day, with biogas production of 131 mL, representing a 10.08% increase compared to the anaerobic digestion without SDAC. For 0.3 g L−1 of myristic acid, complete degradation was achieved on the ninth day, with biogas production of 88 mL, a 4.8% increase over the anaerobic digestion without SDAC. SDAC accelerated the degradation of palmitic acid and lauric acid, completing degradation in 9 and 12 days, respectively, though no significant increase in biogas production was observed. This experiment utilized sludge from wastewater treatment plants to produce SDAC, which was then introduced into the anaerobic digestion process. This method addresses sludge retention while also promoting anaerobic digestion.