Bioaugmentation with cold-tolerant methanogenic culture to boost methane production from anaerobic co-digestion of cattle manure and corn straw at 20℃

Low methane yield and long digestion period are common issues encountered in psychrophilic anaerobic digestion (AD). To address these challenges, this study successfully acclimatized a cold-tolerant methanogenic consortium and applied it as bioaugmentation seed to enhance the psychrophilic AD. Various doses (4%, 8%, 12%, 14%, and 16%) of the bioaugmentation seed were introduced to boost the batch psychrophilic AD of cattle manure and corn straw. Results demonstrated that bioaugmentation increased the methane yield by 3.4–4.8-fold, shortened T80 time by 28–34 d, and reduced VFAs contents by 21.61%-49.23%. The optimal dose for bioaugmentation on psychrophilic AD was 12%, increasing methane yield from 15.40 mL g-1VS to 73.01 mL g-1VS. Microbial community analysis revealed that increase in relative abundance of propionate-oxidizing bacteria and the dominant methanogens (Methanosarcina, Methanothrix) were the key to accelerating the rate-limiting step, i.e., conversion of accumulated propionate and acetate to methane. These findings suggest that bioaugmentation with cold-tolerant methanogenic consortium is a potential approach to boost the psychrophilic AD process, and provide theoretical guidance for commercial biogas plants in cold regions.