Life-cycle energy efficiency and environmental impacts of bioethanol production from sweet potato

► The net energy ratio and net energy gain values were 1.48 and 6.55MJ/L, respectively. ► The most significant environmental impacts were eutrophication and acidification. ► The main sources contributing to energy consumption and environmental impact were analyzed. ► Sensitive factors were identified, and improvement measures were discussed. Life-cycle assessment (LCA) was used to evaluate the energy efficiency and environmental impacts of sweet potato-based bioethanol production. The scope covered all stages in the life cycle of bioethanol production, including the cultivation and treatment, transport, as well as bioethanol conversion of sweet potato. Results show that the net energy ratio of sweet potato-based bioethanol is 1.48 and the net energy gain is 6.55MJ/L. Eutrophication is identified as the most significant environmental impact category, followed by acidification, global warming, human toxicity, and photochemical oxidation. Sensitivity analysis reveals that steam consumption during bioethanol conversion exerts the most effect on the results, followed by sweet potato yields and fertilizers input. It is suggested that substituting coal with cleaner energy for steam generation in bioethanol conversion stage and promotion of better management practices in sweet potato cultivation stage could lead to a significant improvement of energy and environmental performance.