Cascading Valorisation of Agri-Food Waste in Circular Biorefineries: A Critical Review of Technology Integration, Life Cycle Assessment and AI-Assisted Decision Support

Agri-food waste contains fermentable carbon, nutrients and functional compounds, yet its variable composition prevents a universal technology choice. This structured critical narrative review evaluates how cascading recovery can combine high-value compound extraction, biological conversion and thermochemical processing to retain the highest feasible value from unavoidable residues. The review links feedstock characteristics and logistics to configuration choices, positions biohydrogen as a complementary energy pathway, and examines the role of life cycle assessment (LCA) and artificial intelligence (AI) in system design. Wet carbohydrate-rich streams can be routed after selective extraction to fermentation or anaerobic digestion, whereas drier and recalcitrant fractions are more suited to pyrolysis or gasification when drying and gas-cleaning requirements are justified. Wet digestate and other moisture-rich residuals may support nutrient recovery and hydrothermal carbonisation. Dark fermentation is most valuable when its residual effluent is further valorised, for example, through anaerobic digestion. Life cycle outcomes depend on the functional unit, system boundary, co-product treatment, transport, energy demand and direct emissions. AI can improve adaptation to feedstock variability only when the underlying data, models and environmental assumptions are transparent and validated.