Bioconversion of organic waste to value-added products

The escalating generation of organic waste driven by rapid urbanization, population growth and intensification of agricultural and industrial activities poses critical challenges to environmental integrity and resource sustainability. Within the emerging paradigm of circular bioeconomy, the biological conversion of organic waste into value-added products has gained prominence as transformative strategy for simultaneous waste mitigation, resource recovery and decarbonization. This review provides comprehensive and integrative assessment of key bioconversion pathways—including anaerobic digestion, submerged and solid-state fermentation, composting, insect-mediated bioconversion and bioelectrochemical systems for the production of biofuels, biofertilizers, organic acids, biopolymers, enzymes and other high-value bioproducts from diverse organic waste streams encompassing agricultural residues, food waste, municipal organic fractions, livestock manure and agro-industrial by-products. The physicochemical characteristics of feedstocks, microbial community dynamics, enzymatic mechanisms and critical process parameters (pH, temperature, C/N ratio, organic loading rate and hydraulic retention time) governing conversion efficiency and product selectivity are systematically examined. Furthermore, the role of physical, chemical and biological pretreatment strategies in enhancing substrate accessibility and overall bioconversion performance is critically evaluated. The review uniquely integrates recent advances in microbial engineering, CRISPR-based genome editing, synthetic biology and artificial intelligence-driven process optimization with techno-economic assessment and life cycle analysis frameworks to evaluate the feasibility, scalability and environmental sustainability of integrated biorefinery systems. Current bottlenecks including feedstock variability, process instability, energy-intensive downstream processing and economic constraints are identified alongside emerging solutions such as cascading bioconversion, co-digestion, hybrid processing and modular decentralized biorefineries. Bridging fundamental biological mechanisms with industrial-scale implementation within circular bioeconomy frameworks, this review provides holistic roadmap for advancing efficient, economically viable and environmentally sustainable organic waste valorization systems.