Sustainable valorisation of fish processing byproducts through integrated biorefinery approaches

Fish processing waste represents a significant, underutilized biomass resource, with global annual production typically estimated at 50–130 million tonnes. Current disposal methods, such as landfilling and ocean dumping, contribute to eutrophication, nutrient enrichment, and climate change. Additionally, food system assessments indicate that waste accounts for approximately 8% of greenhouse gas emissions. This review consolidates existing evidence on the zero-waste valorisation of fish byproducts within circular bioeconomy frameworks, analysing technological feasibility, environmental performance, and regulatory constraints. The analysis investigates significant side streams, including scales, skin, bones, viscera, heads, oils, swim bladders, crustacean exoskeletons, fins, and livers, focusing on compositional variability and its implications for process design. The evaluation of key extraction and conversion routes includes enzymatic hydrolysis, ultrasound-assisted processing, microwave-assisted processing, supercritical fluid extraction, and pulsed electric field treatment, with an emphasis on recovery yield, functional quality, and energy intensity. Integrated biorefinery configurations achieve over 70% resource recovery and reduce greenhouse gas emissions by 50–75% compared to disposal. However, outcomes depend on feedstock logistics, stabilization, and the integration of unit operations. Persistent barriers encompass sanitary compliance, cross-batch standardization, contaminant surveillance and removal, and substantial capital requirements, which disproportionately hinder operators in small-scale and developing countries. Research priorities encompass techno-economic assessment, life-cycle impact quantification, regulatory harmonization, and quality specifications, as well as policy implements that mitigate investment risks and expedite deployment.