Direct Dilute Acid Hydrolysis of Spent Coffee Grounds: A New Approach in Sugar and Lipid Recovery

摘要

The conventional approach in the production of biofuels from biomass requires lipid extraction prior to hydrolysis for sugar recovery. This study investigated a new approach in the valorization of spent coffee grounds (SCG) by employing direct hydrolysis of non-delipidated SCG expecting to recover the available lipids in the solid residue present in higher concentrations. Sugar content (43-49%) as determined with the proposed approach and expressed in extractive-free basis, were comparable to that of conventional approaches employing lipid extraction prior to hydrolysis (41-51%). Experiments employing dilute acid hydrolysis were carried out under various sulfuric acid concentrations (1-5% v/v H2SO4) and hydrolysis times (30-180 min). A maximum sugar yield of 29% (similar to 62% recovery) was obtained at a solvent-to-solid ratio of 8 mL/g with 5% v/v acid and a hydrolysis time of 3 h. Hydrolysates obtained contain 33.4 g/L of sugar, 0.056 g/L 5-HMF and 0.012 g/L furfural. Also, it was found that lipids remained intact even after hydrolysis and were successfully recovered with lipid recoveries of 99-103%. Solid residues after hydrolysis were similar to 68% of the initial biomass having a moisture content of similar to 65%, thus reducing the total amount of moisture to be removed and energy required in the drying step prior to lipid extraction.