Synergistic Effects of Volatile Fatty Acids and Ammonia Nitrogen on Dry Anaerobic Digestion of Pig Manure and Corn Straw

Abstract

Dry anaerobic digestion is vulnerable to volatile fatty acids and total ammoniacal nitrogen. Moreover, the synergistic effects of volatile fatty acids and total ammoniacal nitrogen are unclear. Therefore, we investigated the combined effects of volatile fatty acids and ammonia nitrogen on dry anaerobic digestion using pig manure and corn straw. Adding 2, 5, or 8 mg/g acetic acid increased volatile fatty acid accumulation, whereas adding 1 mg/g urea mitigated volatile fatty acid accumulation. Adding urea facilitated the enrichment of the Caldicoprobacter and Methanosarcina genera, enhanced the expression of functional enzyme genes involved in the acetoclastic-methanogenesis pathway, and ultimately facilitated methane production. Adding 5 mg/g urea resulted in ammonia inhibition, leading to a significant accumulation of volatile fatty acids. Clostridium_sensu_stricto_1 hindered methane production through hydrolysis and acidification, causing competition between Methanosarcina and Methanoculleus. This inhibition affected the hydrogenotrophic-methanogenesis pathway. The results provide valuable insights into methane regulation during dry anaerobic digestion.

Keywords: Dry anaerobic digestion, methane production, Synergistic facilitate, Synergistic inhibition, Metabolic pathway