Investigation of Waste Coffee Ground as a Potential Raw Material for Biodiesel Production

Abstract

In this study, the utilization of waste coffee ground for biodiesel production was investigated. Waste coffee ground sample was collected from TOMOCA PLC, Addis Ababa, Ethiopia. The oven dried sample was then soxhlet extracted using n-hexane to yield 19.73 %w/w oil. The biodiesel was obtained by a two-step process, i.e. acid catalyzed esterification followed by base catalyzed transesterification using catalysts sulfuric acid and sodium hydroxide respectively. The conversion of waste coffee ground oil in to biodiesel, was about 73.4%w/w. Various parameters that are essential for biodiesel quality were evaluated using the American Standard for Testing Material (ASTM D 6751- 09) and all comply with the specification except acid value. The fatty acid composition of the biodiesel was analyzed by Gas chromatography and the major fatty acids were found to be linoleic acid (39.8%), palmitic acid (37.6%), oleic (12.7%), and stearic acid (7.6%). In addition, preliminary investigation on the solid waste remaining after oil extraction was conducted for possible use as a feedstock for the production of bioethanol. Hydrolysis of the spent of waste coffee ground was carried out using dilute sulfuric acid followed by fermentation using Saccharomyces cereviciae, and resulted in bioethanol yield of 8.3 %v/v. Furthermore, the solid waste remaining after bioethanol production was evaluated for compost (21.9:1 C/N) and solid fuel (20.8 MJ/Kg) applications. The results of this research work give insights on the production of biofuel from waste groud coffee. In addition, the preliminary analysis on the solid waste after the extraction of the oil suggests that it can be used as fuel hence alleviating major disposal problems.