Publications

This study investigates the effect of varying cost and process parameters on bioethanol production rate and the minimum bioethanol selling price (MBSP) during large-scale production of second-generation bioethanol from Sila sorghum stalks found in Kenya. Aspen Plus was used to model and simulate the process that was considered in this study. The flow rate of biomass was varied between 10,000 and 300,000 kg/h which gave rise to a bioethanol flow rate of between 2134.49 and 62,707.33 kg/h. Bioethanol production rate decreased from 21,759.5 to 19,397.6 kg/h when the feed stage position in the beer column increased from 2 to 8. MBSP increased from $0.81/L to $1.11/L when the cost of biomass was varied from $20/tonne to $100/tonne. MBSP increased from $0.9/L to $1.0/L when the cost of enzymes was varied by − 50% and + 50%. MBSP increased from $0.83/L to $1.54/L when discount rate varied by 5% and 30%. MBSP increased from $0.85/L to $1.06/L when fixed capital investment was varied by -35% and + 35%. MBSP reduced from $1.28/L to $0.95/L when plant life varied from 10 to 30 years. MBSP increased from $0.89/L to $0.99/L when income tax rate varied from 0 to 40%. The study indicates that second-generation bioethanol is able to compete with gasoline in Kenya when no levies and taxes are imposed on the MBSP, at a plant life of 15 years and beyond and at an income tax rate of between 0 to 40%.