Journal of Agriculture and Ecology Research International

Aquaculture is increasingly important to global food systems, yet its expansion depends on reliable supplies of nutritionally balanced and environmentally responsible feed ingredients. Fishmeal and fish oil remain valuable because of their nutrient density and palatability, but their availability, price volatility, and ecological implications have encouraged research into alternative resources. Agricultural residues and agro-industrial by-products offer opportunities to recover proteins, lipids, carbohydrates, minerals, pigments, and functional compounds while reducing disposal burdens. This comprehensive review examines the suitability of crop residues, fruit and vegetable by-products, oilseed meals, brewery residues, animal manures, aquaculture sludge, and other agro-industrial streams for aquafeed development. It evaluates physicochemical, chemical, enzymatic, and biological processing approaches, including extrusion, hydrolysis, fermentation, insect bioconversion, algal cultivation, and single-cell protein production. The review emphasises that waste-derived ingredients cannot be assessed solely on crude composition: digestible nutrient supply, anti-nutritional factors, contaminants, palatability, process yield, energy demand, water consumption, and supply-chain traceability must be considered together. A systems framework is proposed that links feedstock characterisation, hazard screening, bioprocessing, formulation, feeding trials, life-cycle assessment, and circular nutrient recovery. Evidence from recent reviews indicates promise for fruit by-products, fermented plant proteins, insect meals, brewery residues, and microbial ingredients, while also revealing substantial variation among species and processing conditions. Future research should prioritise standardised testing, techno-economic analysis, transparent life-cycle assessment, regional value-chain design, and regulatory harmonisation. Agricultural waste valorisation is therefore best understood as a context-specific portfolio of technologies rather than a single universal replacement for conventional feed ingredients.