Green Valorization of Coffee Industry Residues: Emerging Innovations and Their Role in Sustainable Food and Feed Applications

The coffee industry produces substantial amounts of by-products, including pulp, husk, silverskin, and spent coffee grounds (SCG), which are often discarded as waste. These residues are, however, rich in valuable bioactive compounds, dietary fiber, proteins, and lipids, offering significant potential for sustainable valorization. This review provides a comprehensive synthesis of recent advancements in the green valorization of coffee industry residues, with a particular focus on their applications in food and feed systems. It explores the compositional properties of various coffee by-products and examines a wide range of emerging transformation technologies. These include biological processes such as fermentation for producing organic acids, enzymes, and single-cell proteins; green extraction techniques such as supercritical CO₂, microwave-assisted, and ultrasound-assisted extraction for the recovery of antioxidants, caffeine, and phenolic compounds; and chemical conversions like hydrolysis and Maillard reactions to generate fermentable sugars, prebiotics, and flavor compounds. Novel approaches such as solid-state fermentation and encapsulation are also discussed for their potential to enhance the functional value of these residues. The valorization of coffee by-products not only supports environmental sustainability but also contributes to the development of circular food systems. Particular attention is given to the role of these innovations in improving food and feed quality. Addressing key challenges, including variability in residue composition and integration into supply chains, is essential to fully realize the potential of coffee industry by-products in future food and feed innovation.