Valorization of coffee processing by-products for circular economy: Environmental, food, pharmaceutical applications, and artificial intelligence-based optimization approaches.

The global coffee industry generates over 10 million metric tons of coffee processing by-products every year (∼0.9 kg of waste, from cherry to cup, per 1 kg of coffee cherries harvested), posing a significant waste management challenge. This review presents a transdisciplinary synthesis on transferring coffee processing by-products (CPBs) from a substantial waste burden into a valuable resource across the environmental, food, and pharmaceutical sectors to promote sustainable circular economy principles. CPBs demonstrate significant potential for environmental applications in six core areas: carbon dioxide capture, activated carbon production, wastewater treatment, biofuel production, natural dyes production, and agricultural soil remediation. In food applications, CPBs can be effectively used as functional ingredients in gluten-free products, natural antioxidants, and dietary fiber sources (e.g., coffee silverskin contains up to 77% fiber). Pharmaceutical applications utilize their bioactive compounds, including melanoidins (17.0‒23.0 g.100 g-1, dry weight basis), chlorogenic acids (1%‒3%, on a dry basis), and caffeine (1%‒6%, on a dry basis), for antioxidant, antimicrobial, and anti-inflammatory activities. The integration of artificial intelligence offers unprecedented opportunities to optimize the valorization efficiency of CPBs by enhancing their characterization, extraction processes, and supply chain management. However, significant research gaps remain regarding standardized protocols, large-scale CPBs processing technologies, and their economic viability assessments, which should be considered in future research to improve the productivity and efficiency of CPBs applications. Overall, the strategic valorization of CPBs through circular economy principles and advanced technologies offers a transformative pathway toward a sustainable and resilient global coffee industry.