Spent coffee grounds make much more than waste: Exploring recent advances and future exploitation strategies for the valorization of an emerging food waste stream

Coffee is one of the most popular beverages, directly linked with tradition, highlighting its cultural and social effect worldwide. Coffee consumption has been continuously increasing, generating huge amounts of solid residues in return in the form of Spent Coffee Grounds (SCG). In recent years, global environmental awareness and strict legislation have driven research towards the implementation of sustainable processes. Innovative and environmentally sound methodologies for the exploitation of waste-streams have gained interest among the scientific community. In the frame of circular economy, wastes are perceived as sources for the recovery of high value-added compounds. In this review, several scenarios, regarding the exploitation of this low-cost feedstock with huge valorization potential, are being presented via either physicochemical or biotechnological routes.