Energy balance and GHG emissions of cassava-based fuel ethanol using different planting modes in China

Cassava-based fuel ethanol (CFE) is playing an increasingly important role in renewable transportation energy in the Guangxi Province in China. Previous studies have evaluated the energy and greenhouse gas (GHG) performance of CFE, but they have largely overlooked the influences of different agricultural planting modes. In this study, five scenarios related to cassava planting modes were selected to evaluate the lifecycle energy balance and GHG emissions of the CFE system. The results show that, although all the five CFE scenarios show positive net energy values (NEV) and GHG emissions savings compared with the conventional gasoline, the planting modes have significant impacts on their energy and GHG performance. Modes that are considered intensive (i.e. high fertilizer use intensity and highly mechanized harvesting) generally show poorer performance than the extensive ones, primarily because of the intensive energy consumption and GHG emissions during nitrogen fertilizer production, the N2O emission of nitrogen fertilizer use, and higher yield loss rate caused by mechanized harvesting. This study shows that it is important to evaluate the planting modes when producing bioethanol in order to gain an understanding of the life-cycle energy use and GHG performance.