Advances in manganese-based additives for optimizing composting processes and enhancing compost quality

The application of exogenous additives has become a crucial means to promote compost maturation and improve the quality of compost products. Manganese-based additives, due to their unique multivalent redox properties, catalytic functions, and regulatory effects on microbial metabolic networks, have emerged as a research hotspot in the composting field by enhancing the composting process through multidimensional mechanisms. This review summarizes the research progress on the application of manganese-based additives in composting systems, with a comprehensive analysis of their effects on the transformation of organic components, greenhouse gas mitigation, humification processes, and the safety and quality of compost products. Through comparative analysis of the efficacy of various manganese-based additives, the study systematically elucidates the intrinsic relationships between types, functions, and outcomes, as well as the underlying mechanisms. The rational application of manganese-based additives can effectively enhance organic component transformation, mitigate emissions of greenhouse gases and malodorous compounds, strengthen abiotic and biotic humification pathways, and improve the quality and safety of compost products. The types or dosage of manganese-based additives and composting feedstocks significantly influence the transformation of humification precursors, functional microbial community structure, and key enzyme activities, thereby regulating humification processes, mitigation of harmful substances, and quality of compost products. However, current research exhibits limited understanding of the migration and transformation patterns of emerging contaminants during manganese-based additive-enhanced composting processes, along with associated mechanisms. The environmental impact assessment of compost products application in farmland requires further refinement. Furthermore, the differences in the enchancing effects among various manganese-based additives and their dose-effect relationships necessitate in-depth investigation. This paper aims to provide a comprehensive review for in-depth research, technical optimization, and widespread application of manganese-based additives in composting, thereby facilitating the transition of organic solid waste resource utilization towards highly efficient and low-carbon directions.