Composting as a pathway for organic waste valorization: substrate performance, process strategies, and quality benchmarks

Abstract Organic waste is inherently biodegradable and presents a dual challenge. It can either be transformed into a valuable resource or become a major source of environmental pollution if mismanaged. Composting offers a practical and low-cost valorization pathway, simultaneously mitigating environmental impacts and enhancing soil fertility. This review synthesizes current knowledge on the physicochemical characteristics of diverse organic wastes; including agricultural residues, animal by-products, municipal solid waste fractions, and industrial residues and examines their influence on composting performance. Particular emphasis is given to enhance composting strategies and indicators of compost quality are critically assessed. The findings underscore that composting outcomes are highly dependent on substrate composition and management conditions, but that tailored strategies can significantly enhance process performance and product quality. Nevertheless, key research gaps remain particularly regarding the long-term effects of compost application on soil nutrient dynamics, crop productivity, and environmental safety under field conditions. Situating composting within the broader framework of the circular economy and the United Nations Sustainable Development Goals, this review highlights its pivotal role in advancing sustainable waste management, climate change mitigation, and resilient agricultural systems.