Sustainability Study Of Sugarcane And Sweet Sorghum As Feedstocks For Biotehanol Production

Sustainability study of bioethanol production from sugarcane and sweet sorghum was conducted using superPro® Designer and OpenLCA sustainability softwares. The model incorporated the different bioethanol production technologies: pretreatment (sterilization), fermentation and purification. The paper confronted the challenge of fossil fuel derived environmental damages of GHG emission and economic implications of dwindling crude oil prices. This study is aimed at efficient production and consumption of sugarcane and sweet sorghum-based fuel-grade bioethanol with the established economic minimum bioethanol plant capacity of 95 000 m ³/annum.

Based on the economic sustainability indices assessed, the plant using sugarcane had a higher return on investment (ROI) of 26.64% than that utilizing sweet sorghum (18.34%). Their corresponding payback periods were estimated to be 3.75 and 5.5 years respectively. Hence, sugarcane is a more economically viable feedstock for bioethanol production at an annual plant capacity of 95,000 m ³. The environmental assessment conducted on the two feedstocks using life cycle assessment approach in OpenLCA sustainability software showed that the process utilising sugarcane posed lesser environmental burden with higher net energy balance (NEB) of 7.6 but lower net energy renewability (NER) of 50.8. The results of environmental assessment showed that CO ₂ emissions in the sugarcane and sweet sorghum processes constituted the highest pollutants emission/discharge costs with about 98% and 98.53% respectively. The lost work analyses of the feedstocks processing showed that distillation columns were the least energy efficient units in both processing plants recording 24.65% and 22.90% for sugarcane and sweet sorghum plants respectively. Although the total lost work in sweet sorghum process (62,506.68kW) was higher than that of sugarcane process (41,581.14kW). Hence, sugarcane is economically and environmentally more sustainable as feedstock for fuel-grade bioethanol production than sweet sorghum.