Temperature plays a crucial role in determining the operational performance of the anaerobic digestion process. However, a systematic comparison between mesophilic and thermophilic regimes for the anaerobic co-digestion of diverse agricultural residues in terms of biogas production and antibiotic degradation is still lacking. Herein, anaerobic co-digestion of cow manure, chicken manure, corn stover, and wheat straw was investigated under mesophilic (37 °C) and thermophilic (55 °C) conditions using biochemical methane potential testing. The tests were conducted in 500 mL serum bottles with a 350 mL working volume, using acclimated biogas slurry as the inoculum at a substrate-to-inoculum ratio of 3:1 on a volatile solid basis. Methane production, physicochemical parameters, concentrations of three quinolone antibiotics and microbial community were analyzed. The results showed that during the initial 10-day period, daily methane production was consistently higher in the mesophilic digester than in the thermophilic digester. Total methane production over 45 days was approximately twice as high in the mesophilic system. Ammonia, chemical oxygen demand, and volatile fatty acid concentrations were significantly higher under thermophilic conditions, indicating that elevated temperature accelerated the hydrolysis and acidogenesis stages of the anaerobic digestion process. Hydrogenotrophic methanogens (Methanobrevibacter) dominated in both the thermophilic and mesophilic systems, but acetoclastic methanogenesis (Methanosarcina) was more active during the anaerobic digestion process under mesophilic conditions, which likely contributed to its higher overall methane yield. Furthermore, the removal rates of enrofloxacin and ofloxacin in the thermophilic group exceeded those in the mesophilic group by approximately 8%. Overall, anaerobic co-digestion of these four agricultural wastes at 37 °C was more favorable to the methane production, whereas digestion at 55 °C enhanced the degradation of organic substances, including the three quinolone antibiotics. This study highlights the critical role of temperature in shaping microbial communities and provides valuable guidance for temperature selection in the co-digestion of diverse agricultural residues.
Zhu et al. (Tue,) studied this question.