A Life Cycle Comparison of Alternative Transportation Fuels

The paper analyzes energy use and emissions per GJ of various fuels delivered to the vehicle fuel tank, covering extraction, fuel production, transportation, storage, and distribution phases of the life cycle of alternative fuels. Drawing on a number of existing studies, the modeling issues and approaches, main results and insights are summarized. The range of estimates in various studies is large; however, common patterns can be observed. The analysis indicates, that conventional gasoline fuel cycle has robust advantages with respect to energy efficiency, conventional pollutant emissions, and most importantly, existing infrastructure compared to alternative fuels. Fossil fuel based alternatives like CNG, NG-Methanol, NG-FTL do not result in significant improvement in fuel cycle environmental performance. Biofuels offer the benefits of lower and even negative GHG emissions, sustainability, and domestic fuel production. The herbaceous and woody biomass-based ethanol options are more attractive than producing ethanol and biodiesel from food products.