Search

Composting process is accompanied by the emission of greenhouse gases such as nitrous oxide (N 2 O). Biochar addition effectively reduced the release of N 2 O. However, the specific impact mechanism of biochar is unclear. Therefore, the aim of this study was to reveal the response of N 2 O-related microorganisms to biochar addition during chicken manure composting. Results suggested that the addition of biochar reduced the species of N 2 O-related microorganisms from 22 to 19, and changed the functional roles. Network analysis further revealed that the addition of biochar weakened the transformation relationship between nitrification and denitrification, which effectively inhibited the denitrification rate. Ultimately, Structural equation models verified that the addition of biochar made core microorganism Ornithinibacillus prevail, which weakened the denitrification during composting. This study identified the core microorganisms that regulated the production of N 2 O during chicken manure composting, and provided a theoretical basis for the targeted regulation of N 2 O emission. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • MnO 2 improved the humification degree of FA components in composting. • Core bacteria associated with FA components transformation were identified. • Core bacteria could be divided into transforming and processing bacteria. • Transforming bacteria was a dominant factor in transfotmation of FA components. Here, we revealed the effects of microbes on fulvic acid (FA) formation in composting by adding MnO 2. The results showed that the MnO 2 promoted the formation of highly humified components (79.2% increased for component 2, and 45.8% increased for component 3) in FA. Additionally, core bacteria involved in FA transformation were identified, the MnO 2 increased the relative abundance of core bacteria. Notably, two different core bacteria types were identified: "transforming bacteria" and "processing bacteria". The "transforming bacteria" dominated (about 40% contribution) in the formation of FA components with a high humification degree. The structural equation model confirmed that "transforming bacteria" could convert partly FA components with low humification into highly humified components, and the "transforming bacteria" could be regulated by environmental factors. These findings provided a new insight to manage FA humification degree during composting and helped to improve the application value of FA. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen Pollution risks in chicken manure composting (CM) was continuous. • Maximum total nitrogen content and pollution risk were observed in CM. • Pollution risks of municipal solid and straw waste concentrated in heating phases. • Pollution risk from denitrification was the most serious in municipal solid waste. • The genes (pmoC-amoC , nrfH , nifD etc.) were related to nitrogen pollution risks. The aim of this study was to evaluate nitrogen pollution risks from distinct materials composting with the discrepancy of component, including chicken manure, municipal solid and straw waste (CM, MSW, SW). Results showed total nitrogen maximum mean concentrations were observed in CM (39.57 g/kg). Pollution risks in CM were continuous, while MSW and SW mainly concentrated during heating phases. Microbial analysis confirmed that pollution risks from ammonification and nitrification were more prevalent in CM. The risks of pollution caused by nitrate reduction accompanied N 2 O were the most serious in MSW. The multifunctional nitrogen-related microbes P seu domonas and Bacillus were affected by microenvironments and contributed to different pollution risks. Furthermore, PICRUSt analysis identified the "inferred" key genes (pmoC-amoC , nrfH , nifD etc.) related to nitrogen pollution risks. This study evaluated nitrogen pollution risks and proposed the future directions, providing theoretical basis and feasible optimization measures for the mitigation of nitrogen pollution during composting. [ABSTRACT FROM AUTHOR]