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

•High solid methane fermentation of chicken manure was investigated.•Ammonia inhibition was the main problem for stable operation.•The ammonia inhibitive sensitivities for different reactions were evaluated.•Methanogenesis, acidogenesis and hydrolysis were simulated by models.•The seriously inhibited reactor was successfully recovered by dilution.

A 12 L mesophilic CSTR of chicken manure fermentation was operated for 400 days to evaluate process stability, inhibition occurrence and the recovery behavior suffering TAN concentrations from 2000 mg/L to 16,000 mg/L. A biogas production of 0.35–0.4 L/gVSin and a COD conversion of 68% were achieved when TAN concentration was lower than 5000 mg/L. Ammonia inhibition occurred due to the addition of NH4HCO3 to the substrate. The biogas and COD conversion decreased to 0.3 L/gVSin and 20% at TAN 10,000 mg/L and was totally suppressed at TAN 16,000 mg/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 4000 mg/L and 300 mg/L respectively, and the recovered biogas production was 0.5 L/gVSin. 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.

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