Investigation on the Effect of Different Additives on Anaerobic Co-Digestion of Corn Straw and Sewage Sludge

Abstract

The co-digestion of corn straw and sewage sludge with different additives (biochar, magnetic biochar, and Fe₃O₄) were investigated. The highest cumulative methane yield of 245.15 mL/g VS_added was obtained with the optimal Fe₃O₄ addition ratio as 5 g/kg, which was 60.47% higher than that of control. The lag phase time was shortened from 5.46 to 3.82 days with a biochar dosage of 5 g/kg. The performance of Fe₃O₄ on methane production from the co-digestion process was better than that of the biochar and magnetic biochar. The direct interspecies electron transfer (DIET) was enhanced with regard to the increased concentration of acetic acid and decreased concentration of propionic acid. Microbial community analysis showed that the Geobacter and Methanosarcina were selectively enriched on the surface of Fe₃O₄, promoting the DIET and acetoclastic methanogenesis pathway. The cost-benefit analysis of recycling utilization of Fe₃O₄ additives revealed the best economic efficiency during the co-digestion process.

Keywords: methane production, Magnetic biochar, co-digestion, recycling, Cost-benefit analysis