Phosphate, magnesium containing additives and biochar regulate compost maturity and synergistically reduce odor emission in chicken manure composting: Role of physicochemical, bacterial and fungal dynamics.

This study explored the odor composition and emission in chicken manure composting process, employing chemical fixatives and biochar to mitigate odors effectively. Compost maturity, ammonia, sulfur-containing odor emissions, as well as the bacterial and fungal community structure were analyzed to assess composting performance and mechanisms. The results indicated that four malodorous substances were identified as major contributors: dimethyl disulfide (Me2S2), hydrogen sulfide (H2S), methyl sulfide (Me2S), and ammonia (NH3). Biochar (BC) augmented compost maturity by enhancing the relative abundance of Thermobifida and Saccharomonospora, while reducing the emission of total malodorous sulfur-containing components by 65.3% by mitigating Halocella and Hydrogenispora, albeit without affecting NH3 emissions. Superphosphate (SP) mitigated malodorous sulfur-containing components by 51.3% through its calcium (Ca) components and associated bacteria (Pseudomonas, Halocella and Hydrogenispora). Notably, magnesium (Mg) emerged as a limiting factor for NH3 fixation by SP. The combination of SP and magnesium sulfate (MS) decreased NH3 emissions by 47.9% via the formation of struvite crystals (MgNH4PO4) and further reduced the emission of malodorous sulfur-containing components by 60.0% by enhancing functional fungi inhibiting malodorous substance production. Ultimately, the combined application of BC, SP, and MS yielded the most significant odor reduction effects, with reductions of 86.8%, 35.3%, 92.8%, and 38.8% observed in Me2S2, H2S, Me2S, and NH3, respectively.