Development of a fractionation strategy for a spent coffee ground-based biorefinery

Abstract

Biorefineries based on food wastes such as spent coffee grounds (SCG) are of growing interest to the EU owing to the push towards greener production and waste valorization. SCG from café Richard were studied in detail in terms of composition (41.1 % hemicelluloses, 16.2 % lipids, 1.5 % cellulose, 1 % moisture, 1 % ash, 0.4 % proteins, and 21.1 % Klason insoluble residues). Extractible fractions of SCG were studied using con ventional and assistive extractions (ultrasound-assisted and accelerated solvent extractions (ASE)) for different solvents and temperatures. In addition, lignin separation methods such as dioxane organosolv (DO) and soda (NT) treatments were performed to study the non-sugar fraction. Results showed that residues obtained from DO and NT did not behave like lignins and were characterized in detail. The study of extractives at different temperatures showed that hexane showed the highest yield at room temperature (16.6 %). Furthermore, using ASE, methanol extractives (60 °C) yielded the best antioxidant capacity (EC50=0.4 mg/mmol DPPH), while methanol extractives (125 °C) had the highest yields (20.4 %). In addition, water extraction at 180 °C resulted in the extraction of hemicelluloses. Based on the results of this study, an SCG sequential fractionation strategy consisting of hexane-based fractionation of lipids, methanol-based fractionation of antioxidants and water based hemicellulose fractionation are proposed.