Interest has been renewed in bio-ethanol products for their contributions in moderating oil crises. So far, most research on bio-ethanol in China is based on pilot-level experimental studies. But this work only discloses information regarding material balances and reached yields without any further energy analysis. This paper aims to assess the energy efficiency of the cassava-based fuel ethanol (KFE) product from southwest China. For the purpose of a life cycle study of the KFE product as replacement transportation fuel. the study chose a "vehicle fueled by cassava-based E10 (a blend of 10% ethanol and 90% gasoline by volume)" as the subject and accordingly defined the scope of this study. Then, the life cycle model of the KFE product concerning energetically relevant in-and outputs was built. Due to variations in data collected, as well as some estimates and assumptions used in this study, the Monte Carlo method was introduced to develop the statistical dispersion of calculated outputs of the assessing model. Assessment results show that, within the boundary of this study, KFE has a positive net energy value, with an energy ratio of around 0.70 MJ/MJ, which means 7 MJ into the processing for each MJ of KFE output. (c) 2008 Elsevier Ltd. All rights reserved.