Oil Extraction from Spent Coffee Grounds: Experimental Studies and Exergoeconomic Analysis

Abstract

Currently, the spent coffee grounds (SCGs) are considered an agro-industrial waste with a high oil content that can be used as a feedstock in biorefineries. Therefore, the oil extraction from SCGs is considered a main stage, that should be sustainable and low-cost. The aim of this study is to determine and compare the exergetic and economic indicators of two SCGs oil extraction processes: soxhlet extraction (SE) and ultrasound-assisted extraction (UAE). The exergoeconomic balances were performed by using Engineering Equation Solver (ESS). In addition, the effects of the solvent to SCGs ratio on the extraction yield and on the exergoeconomic indicators were studied. The analysis aided by computational tools determined that the exergy destruction rate of the SE process (14.3 kJ/kg) is higher compared with the UAE process (4.50 kJ/kg). Therefore, the oil specific cost is reduced to 86% when using UAE process. Furthermore, in the UAE process, the increase in the hexane to SCGs ratio from 5 mL/g to 20 mL/g, reduces the oil specific cost by 68.5 % and increases the oil extraction yield from 10.5 % to 18.8 %. Future studies should focus on the ultrasound-assisted extraction process scale-up.