Mesophilic methane fermentation of chicken manure at a wide range of ammonia concentration: Stability, inhibition and recovery

A 12L mesophilic CSTR of chicken manure fermentation was operated for 400days to evaluate process stability, inhibition occurrence and the recovery behavior suffering TAN concentrations from 2000mg/L to 16,000mg/L. A biogas production of 0.35-0.4L/gVS_in and a COD conversion of 68% were achieved when TAN concentration was lower than 5000mg/L. Ammonia inhibition occurred due to the addition of NH₄HCO₃ to the substrate. The biogas and COD conversion decreased to 0.3L/gVS_in and 20% at TAN 10,000mg/L and was totally suppressed at TAN 16,000mg/L. Carbohydrate and protein conversion decreased by 33% and 77% after inhibition. After extreme inhibition, the reactor was diluted and washed, reducing TAN and FA to 4000mg/L and 300mg/L respectively, and the recovered biogas production was 0.5L/gVS_in. The extended Monod model manifested the different sensitivities of hydrolysis, acidogenesis and methanogenesis to inhibition. VFA accumulation accompanied an increase in ammonia and exerted a toxic on microorganism.