Valorization of spent coffee grounds with supercritical fluids

Spent coffee grounds (SCGs) are a potential sustainable source of high value added compounds. Extractions with pure supercritical CO2 (scCO2) and scCO2+co-solvents (10% ethanol, 10% i-propanol and 5% ethyl lactate) of SCGs were used for valorization of the waste biomass. Conditions for highest yields (30 MPa and 323 K for extractions with co-solvents and 40 MPa and 313 K - for those with pure scCO2) were identified and applied for comparison. The results, in terms of global yield and elemental composition, were compared with those achieved by pure scCO2 and by conventional Soxhlet extraction with n-hexane. The highest yield of 12.3%was obtained with scCO2+5% ethyl lactate, yields of (10.1 to 12) % - with the rest of the extractions, and 10.4 %-by the Soxhlet extraction. Quantitative identification of diterpens in the extracts was carried out by H-NMR. Elemental analysis provided useful information for the application of SCGs products, obtained with the tested extraction technologies.