Reducing nitrogen losses in chicken manure composting with acetic acid: Importance of rare bacteria in nitrogen transformation during the thermophilic phase

Abstract

This study investigated the effect of acetic acid on reducing nitrogen losses in pilot-scale chicken manure composting and provided a comprehensive analysis of the distinct roles of abundant and rare bacteria in nitrogen transformation. Acetic acid was added at concentrations of 4.05 (AAL) and 8.09 g/kg (AAH), and physicochemical parameters, ammonia emissions, and bacterial communities were monitored. AAL and AAH reduced thermophilic-phase ammonia emissions by 27.67 % and 12.81 %, respectively, contributing to 53.48 % and 43.34 % of overall nitrogen loss reductions, respectively. Acetic acid enriched rare taxa rather than abundant taxa in the thermophilic phase, which contributed to reduced ammonia emission in AAH by promoting nitrification and ammonia assimilation. Network analysis indicated that nitrogen conversion was related to rare taxa interactions (p < 0.001) rather than abundant taxa interactions, while the relationship was enhanced in AAL but not in AAH. For community assembly, rare taxa were more affected by stochasticity than abundant taxa, while AAH enhanced the stochasticity of rare taxa (p < 0.05) but did not affect that of abundant taxa. Rare taxa assembly was related to nitrogen transformation (p < 0.05), while abundant taxa assembly was not. These results indicated that rare taxa responded differently to varying doses of acetic acid. This study demonstrated that a lower dose of acetic acid was more effective in reducing ammonia emissions during the thermophilic phase of composting and highlighted the importance of rare taxa in nitrogen transformation. This study will promote the application of organic acids for nitrogen retention in manure composting.