Ammonia stripping by in situ biogas self-circulation to mitigate ammonia Inhibition in high-solids anaerobic digestion of chicken manure.

High-solids anaerobic digestion (HSAD) of chicken manure is severely limited by ammonia inhibition. Previous studies using moderate stripping achieved only partial total ammonia nitrogen (TAN) reduction and modest methane enhancement, with persistent volatile fatty acid (VFA) accumulation and process instability. This study demonstrated that higher-frequency ammonia stripping via in situ biogas self-circulation significantly outperforms conventional methods. Implementation resulted in 46.1% TAN removal (from 8.0 to 4.3 g/L) and a 60.4% increase in methane yield (404.2 vs. 254.4 mL/g volatile solids in the control). Mass balancing confirmed a 71.4% substrate-to-methane conversion efficiency and a 43.1% reduction in VFA accumulation. Microbial community analysis revealed a marked shift: ammonia-tolerant taxa (e.g., MBA03 and Pseudomonadales) dominated the control, whereas the stripping system enriched hydrolytic/fermentative consortia (e.g., Clostridiales and Bacteroidales) rather than a broad increase in microbial diversity. The archaeal communities transitioned from Methanoculleus to Methanobacterium dominance, which was correlated with 15.5% greater specific methanogenic activity. Collectively, these results indicate that in situ ammonia stripping via biogas self-circulation markedly mitigates ammonia toxicity, stabilizes HSAD processes, and substantially enhances methane production from chicken manure.