Fruit Waste as a Resource for Biofuel Production and High-Value-Added Compounds

Residues generated during fruit processing constitute an abundant and underutilized biomass rich in bioactive compounds, pigments, structural polysaccharides, lipids, and fermentable carbohydrates. Although their potential for biorefinery applications is widely recognized, existing studies are often fragmented, focusing on isolated products, which limits a comprehensive understanding of integrated valorization strategies. To address this gap, this study presents an integrative review supported by bibliometric analysis to identify global research trends, dominant technological pathways, and key challenges associated with the use of fruit residues in biorefineries. The review covers technologies for extracting phenolic compounds, essential oils, pigments, and structural fibers, as well as lipid recovery, enzyme production, and biochemical routes for bioethanol, biohydrogen, and biogas generation. The review reveals that emerging technologies, such as pressurized fluid extraction, microwave-assisted extraction, and ultrasound-assisted extraction, enable efficient recovery of antioxidant compounds, high-purity pectin, and fermentable sugars, particularly when applied in sequential and integrated processing schemes. Bioethanol production is the most extensively investigated route, with yields strongly dependent on biomass composition and pretreatment strategies, identifying banana, cashew, apple, mango, coconut, and palm residues as promising feedstocks. In addition, biohydrogen production via dark fermentation and anaerobic digestion for biogas generation shows high technical feasibility, especially when integrated with upstream extraction steps. Overall, integrated valorization of fruit residues emerges as a key strategy to enhance economic performance and environmental sustainability in agro-industrial systems.