Global Warming Impact of Gasoline vs. Alternative Transportation Fuels

The phenomenon of global warming, caused by the increased emissions of CO₂ and other greenhouse gases (CH₄ and N₂O), has received considerable attention from policy makers and environmental groups. The current focus is on the development of global warming strategies based on choice of various transportation fuels for motor vehicles. This paper examines this issue by assessing the global warming impact of gasoline and other alternative fuels such as compressed natural gas (CNG), liquefied petroleum gas (LPG), methanol, and ethanol. The analysis accounts for all emission sources and greenhouse gases that are associated with the entire fuel cycle under a variety of process and engine technology scenarios. Results show that CNG and LPG are comparable to gasoline in total greenhouse gas emissions, while methanol and ethanol generally yield more greenhouse gases than gasoline. The exact differences depend on the assumed process efficiencies, vehicle fuel economy and emissions, and the relative warming affects of CH₄ and N₂O to CO₂. In view of these uncertainties and the fact that transportation fuels are not major contributors to global warming, switching from gasoline to either natural gas or alcohol-based fuels will have little impact on reducing total greenhouse gas emissions.