Bioethanol Production and Optimization Test From Agricultural Waste: The Case of Wet Coffee Processing Waste (Pulp)

Abstract

The objective of this study was to evaluate the feasibility of ethanol production and optimization from coffee pulp by using commercial bakery yeast, i.e., S. cereviciae. To conduct this study, fermentation was held at temperature 30 °C and pH 5. Coffee pulp was hydrolyzed by refluxing, a solid to liquid ratio of 1:10, using dilute sulfuric acid (1, 2 and 4 %) and distilled water at hydrolysis time of 1, 2, 4, 6 and 10 hours keeping boiling temperature. 90 % maximum total sugar concentration was obtained at 4 hours acid free hydrolysis. Based on these hydrolysis results, fermentation process was performed.

In the process, it was observed that ethanol concentration decreased with an increase in acid concentration, hydrolysis time and fermentation time. The maximum result was obtained with distilled water hydrolysis for 4 hours and 24 hours fermentation. Under these conditions maximum ethanol concentration production was 7.4 g/L. The result indicated that being available in plentiful amounts and non-edible material, coffee pulp will be potential feedstock for bioethanol production in Ethiopia.