Upcycling Spent Coffee Grounds: Approaches, Emerging Concepts and Applications

Spent coffee grounds (SCG) are generated in millions of tonnes annually due to rising global coffee consumption, posing significant challenges, including greenhouse gas emissions, waste-disposal problems, and the loss of valuable compounds like caffeine, dietary fibre, phenolics, antioxidants, proteins, and lipids, offering prospects for potential valorization. Its composition is influenced by several factors. This review focuses on recent advancements in the valorization of SCG across sectors such as food, nutraceuticals, bioenergy, and packaging. The emphasis is on pretreatment, extraction, and bioconversion methods, as well as current research gaps, limitations, and future directions. SCG valorization is oriented toward integrated, multi-product biorefinery systems based on green extraction and bioconversion technologies to recover high-value compounds in both the food and non-food sectors. Nonetheless, industrial scalability is limited by composition variability, energy-intensive processing, techno-economic constraints, and safety and regulatory issues that remain unresolved. The shortcomings, such as inadequate standardized characterization, toxicological validation, and pilot-scale studies, are critical gaps. Scalable, energy-efficient processes, AI-assisted optimization, and regulatory alignment development should be a priority in future research, so that sustainable and commercial deployment is possible.