Sustainability Analysis Of Bioethanol Production From Grain And Tuber Starchy Feedstocks

Comparative sustainability study of bioethanol production from selected starchy feedstocks that are abundantly available was carried in this work. This is to ensure safe, reliable, and efficient production and consumption of fuel-grade bioethanol. The analysis utilized the established economic minimum bioethanol plant capacity of 158 000 m ³/annum. The processing flowsheet model utilized was the same for each feedstock. Economic, environmental and energy perspectives of the sustainability study were investigated. The economic and environmental indicators and indices were assessed using SuperPro® Designer and OpenLCA sustainability software packages respectively; exergy and lost work were estimated manually with Microsoft Excel (Microsoft Suite®). The economic sustainability indicator showed that the plants using cassava and sweet potato had the highest return on investment (ROI) of 64.41 and 41.96% respectively. The least profitable plant was based on sorghum recording ROI value of 34.11%. The results of the environmental assessment conducted on the four selected feedstocks showed that the processes utilising cassava, corn, sweet potato, and sorghum recorded encouraging global warming potential (GWP) of 0.2452, 0.2067, 2.5261 and 0.2099 kg CO ₂ equivalent respectively. Cassava and corn emerged as the two most economically viable feedstocks when economic parameters were adjusted to include pollutants emission/discharge costs but with slight decrease in profitability indices. The lost work analyses showed that distillation columns were the least energy efficient units in the four bioethanol production routes assessed, recording loss work of about 61, 68, 34 and 49 MW for cassava, sweet potato, corn and sorghum processing plants respectively. However, the net energy balance (NEB) and energy renewability results of the four production routes showed that the processes utilizing the four selected starchy biomass feedstocks are more sustainable compared to fossil fuel.