Mitigation strategies for ammonia inhibition and coupled regulation of operational parameters in high-solids anaerobic digestion of chicken manure: A critical review.

High-solids anaerobic digestion (AD) of chicken manure offers a promising route for recovering energy from poultry waste, but its high nitrogen content and total ammonia nitrogen (TAN) accumulation constrain stable methane production. This review critically evaluates the effects of feeding total solids (TS), organic loading rate (OLR), hydraulic retention time (HRT), temperature, and ammonia on process performance, with particular emphasis on continuous and semi-continuous AD systems. A quantitative analysis shows that protein degradation is more sensitive to ammonia accumulation than carbohydrate degradation. Methanogenic community analysis further indicates that TAN and OLR jointly regulate community structure, with hydrogenotrophic methanogens generally becoming more prominent under elevated ammonia stress. Based on these relationships, an integrated operating framework is proposed in which OLR and HRT are adjusted according to substrate and ammonia loading, while microbial acclimation and targeted ammonia mitigation are introduced when ammonia stress exceeds microbial capacity. Stable operation of chicken manure AD depends on the interaction between ammonia loading and microbial adaptation rather than a single TS or TAN threshold. This review provides a condition dependent framework for optimizing high-solids chicken manure AD from laboratory operation toward practical engineering application.