Effects of oxygen levels on maturity, humification, and odor emissions during chicken manure composting

Compost quality greatly depends on maturity and humification, and odor emissions can cause severe air pollution and nutrient losses during composting. In this study, a laboratory trial was carried out under different aeration conditions to explore the effects of boundary-oxygen content (microaerobic, aerobic, oxygen-rich) on maturity, humification, and odor emissions during chicken manure composting. Results showed that the aeration rate (AR) of 0.1 m3 h−1 was the minimum aeration requirement to realize the maturity and humification of chicken manure. The germination index (GI) and humification indexes were significantly higher in the aerobic and oxygen-rich treatments (AR ≥ 0.1 m3 h−1) than in the microaerobic treatments (AR < 0.1 m3 h−1). When comparing the maturity and humification of the final compost, the lowest NH3 and H2S emissions occurred in the treatment with continuous aeration at 0.1 m3 h−1. In addition, a greater than 35% reduction in C/N could be used as an evaluation indicator of maturity and humification. Redundancy and correlation analysis indicated that maturity, humification, and odor emissions were significantly influenced by the key physicochemical factors (O2, temperature, NH4+-N and C/N) and key bacterial communities. Finally, an operable and straightforward strategy was proposed to improve compost maturity and reduce odor emissions through controlling temperature, C/N, and NH4+-N to regulate the key bacterial communities.