Nitrogen conversion and mechanisms related to reduced emissions by adding exogenous modified magnesium ore during aerobic composting.

In this study, modified products with a higher specific surface area and pore volume were prepared by light burning magnesite (MS) to increase its magnesium content and surface activity. MS heated at 650 °C (MS650) was applied in aerobic composting to assess its effect on nitrogen transformation during composting and the possible related chemical and microbial mechanisms. Adding MS650 reduced the NH ₃ emissions (0.74-52.4%), N ₂ O emissions (29.0-57.9%), and greenhouse gas emissions (41.8-60.3%), and its effect on reducing nitrogen emissions was negatively correlated with the amount added, where the optimum proportion of MS650 was 2.5%. Struvite precipitation and physical adsorption were the chemical mechanisms responsible for nitrogen retention. MS650 inhibited the growth of nitrifying, nitrate reducing, and denitrifying bacteria. The total organic carbon content, electrical conductivity, and N ₂ O together explained most of the variation (52.7%) in nitrogen functional genes, followed by Proteobacteria (28.6%). These findings have important implications for reducing nitrogen and greenhouse gas emissions, and improving the quality of compost products.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2025 Elsevier Ltd. All rights reserved.)