Waste Valorisation in Floating Aquaculture Systems: Environmental Biotechnology Pathways and Engineering Integration for Circular Resource Recovery

The rapid expansion of aquaculture has led to a substantial increase in the generation of organic waste, nutrient-rich effluents, and residual biomass, creating significant environmental challenges while simultaneously providing opportunities for resource recovery within the circular bioeconomy. Environmental biotechnology offers a broad range of solutions for transforming these waste streams into valuable products, including renewable energy, fertilisers, biochar, microbial biomass, and other bio-based resources. However, the practical implementation of these technologies in floating aquaculture systems remains fragmented due to the lack of integrated engineering approaches. This review critically analyses the current state-of-the-art in environmental biotechnology pathways for aquaculture waste valorisation, covering biological, physicochemical, and thermochemical technologies applicable to floating production systems. The assessment covers anaerobic digestion, composting, insect bioconversion, microalgae cultivation, integrated multi-trophic aquaculture, nutrient recovery, hydrothermal carbonisation, and pyrolysis, together with their technological maturity, offshore applicability, and contribution to circular resource recovery. Beyond reviewing existing technologies, this paper proposes the “Circular Floating Aquaculture Systems Engineering Integration Framework” (CFAS-EIF), a systems engineering concept that integrates floating production infrastructure, waste collection, resource recovery technologies, digital management, and circular value chains into a unified architecture. The framework illustrates how environmental biotechnology can be implemented through coordinated engineering integration, enabling the transition from waste management to resource valorisation in offshore aquaculture. The proposed framework provides researchers, engineers, and industry stakeholders with a comprehensive reference for designing next-generation aquaculture platforms that support sustainable resource management, climate change mitigation, and a circular bioeconomy.