Greenhouse Gas Emissions from Gasoline, Hybrid-Electric, and Hydrogen-Fueled Vehicles

In a recent article, the author showed that it was theoretically possible for plug-in hybrid-electric light transportation vehicles to utilize electricity provided by electric utilities to displace almost 75% of the energy of gasoline used by light transportation vehicles in the United States. It also indicated that replacing this gasoline energy would require 200-250 GW (Gigawatts) of additional electrical generating capacity. (Uhrig, 2005) In an earlier article, the author showed that about 930 GW of additional electrical generating capacity would be required to produce hydrogen by electrolysis to replace all the gasoline used for all transportation in the United States. (Uhrig 2004). Should either of these substitutions be even partially implemented, the choice of fuel for the new generation of electricity and the method of producing hydrogen could either significantly increase or decrease future greenhouse gas emissions. The purpose of this paper is to provide quantitative comparisons of greenhouse gas emissions, specifically carbon dioxide, between all of the various options. The results indicate that greenhouse gas emissions are small or negligible when electricity generated by solar, renewables, or nuclear energy are used either directly or to produce hydrogen. However, when fossil fuels (natural gas, oil, or coal) were used, the greenhouse gas emissions were greater than for gasoline fueled vehicles in most cases. The use of steam methane reforming to produce hydrogen is included in the analysis.