“Zero Waste” and “Green” Approaches towards Valorisation of Vegetable Residues

Among the waste valorisation strategies, particular attention is given to plant and agri-food biomasses. They are particularly valuable since they are produced in large amounts worldwide and have been widely studied since ancient times for the richness in secondary metabolites, displaying strong bioactive properties. Within this context, the following biomasses have been selected and processed for the present study:Residues from medicinal plants (Cucurbita pepo L. seeds and Serenoa repens L. fruits). Given the selectivity of the method employed from the company processing the commercial oils, the residual biomasses are expected to still contain a significant amount of valuable natural products. Coffee silverskin, the only by-product of coffee roasting process. Silverskin has already been investigated as combustible, fertilizer and animal feed, but our work points out the relevance of its phytochemical profile in terms of polar compounds dealing with its antioxidant properties. The aim of the study was to set up a green methodology minimizing the use of organic solvents, employing a green extraction technique, supercritical CO2, selectively enriching the extracts of target high value compounds. Plant biomasses were chosen in order to assess different methodologies, based on the same supercritical fluid technique, able to demonstrate the feasibility to target separately narrow windows of compounds, differentiated by their polarities.