Biofuel production from spent coffee grounds by supercritical ethyl acetate

Abstract

In this work, spent coffee grounds (SCGs) was used as the feedstock for biofuel production by supercritical ethyl acetate. The SCGs is waste obtained from coffee industrial that is continuously increasing every year. To make SCGs becomes more valuable, utilization of ethyl acetate as the extracting and reacting solvents for biofuel production via interesterification reaction. The characterization of SCGs sample showed that the moisture content of fresh SCGs was around 56 wt%. After oven drying, the moisture of SCGs was reduced to 12.76 %wt. To prolong the shelf-life of the sample and to minimize impact of hydrolysis on interesterification reaction, the drying step is required to reduce the water in SCGs. Ethyl acetate was a suitable solvent for coffee oil extraction from SCGs due to high recovery of coffee oil (22.74 wt%). The feedstock for biofuel production was the mixture of coffee oil and ethyl acetate at molar ratio of 1:30 that extracted at room temperature and atmospheric pressure. In biofuel production, two parameters were investigated for optimal condition. Temperature (275, 300, 325, and 350°C) and feed flow rate (2, 2.5, and 3 g/min) were controlled under pressure at 15.0 MPa. The amount of fatty acid ethyl ester (FAEE) in the product was measured by gas chromatography. The optimal condition was found at temperature of 350°C and feed flow rate of 2.5 g/min. The highest yield of FAEE is 86.44 wt%.