Enhancing hyper-thermophilic hydrolysis pre-treatment of chicken manure for biogas production by in-situ gas phase ammonia stripping

Hydrolysis is normally the rate limiting step for anaerobic digestion (AD). In this study, hyper-thermophilic (70 °C) pre-treatment of chicken manure under HRTs of 10, 5, 3, 2 and 1 d(s) was investigated to enhance the hydrolysis efficiency for biogas production. In-situ phase gas stripping was integrated into the pre-treatment reactor to remove ammonia-N and to enhance the hydrolysis performance. The results showed that in-situ gas stripping removed 18%–31% of ammonia-N and improved hydrolysis by 2.6%–31.1%. The methane yield of pre-hydrolyzed chicken manure reached 518 mL g-VS −1 under optimal HRT 3 days, which was 54.6% higher than that obtained from the control reactor. However, shortening HRTs below 3 days resulted in a significant reduction in hydrolysis efficiency. The percent of hydrolysis and acidogenesis bacteria reduced to 40.6% at HRT 1 d. 16sRNA results indicated existence of methanogens in pre-hydrolysis reactor. Further optimizing of ammonia stripping was thus needed for hydrolysis pre-treatment.