Revealing mechanisms of NH 3 and N 2 O emissions reduction in the rapid bio-drying of food waste: Insights from organic nitrogen composition and microbial activity

Inevitably, aerobic biological treatment processes generate emissions of ammonia (NH 3 ) and greenhouse gas (GHGs) emissions, especially nitrous oxide (N 2 O). The rapid bio-drying process (RBD) for food waste (FW) alleviates issues arising from its substantial growth. However, its emissions of NH 3 and N 2 O remain unknown, and the correlation with nitrogen components in the substrate remains unclear, significantly impeding its widespread adoption. Here, the nitrogen loss and its mechanisms in RBD were investigated, and the results are as follows: The total emission of NH 3 and N 2 O were1.42 and 1.16 mg/kg FW (fresh weight), respectively, achieving a 98 % reduction compared to prior studies. Structural equation modeling demonstrates that acid ammonium nitrogen (AN) decomposition chiefly generates NH 3 in compost ( p  < 0.001). Strong correlation (p < 0.001) exists between amino acid nitrogen (AAN) and AN. In-depth analysis of microbial succession during the process reveals that the enrichment of Brevibacterium, Corynebacterium, Dietzia, Fastidiosipila, Lactobacillus, Mycobacterium, Peptoniphilus, and Truepera, are conducive to reducing the accumulation of AN and AAN in the substrate, minimizing NH 3 emissions ( p  < 0.05). While Pseudomonas, Denitrobacterium, Nitrospira, and Bacillus are identified as key species contributing to N 2 O emissions during the process. Correlation analysis between physicochemical conditions and microbial succession in the system indicates that the moisture content and NO 3 − levels during the composting process provide suitable conditions for the growth of bacteria that contribute to NH 3 and N 2 O emissions reduction, these enrichment in RBD process minimizing NH 3 and N 2 O emissions. This study can offer crucial theoretical and data support for the resource utilization process of perishable organic solid waste, mitigating NH 3 and GHGs emissions.