experience, taking into account the increased mileage per gallon of conventional vehicles. The second trajectory shows the estimated consumption of gasoline if hydrogen vehicles were never adopted and hybrids captured the entire market share that would have been captured by hydrogen vehicles. In the discussions that follow, the committee considers the impact on gasoline consumption of a transition to hybrid vehicles. That impact can be seen as the difference in Figure 6-4 between the gasoline consumption and the consumption with hydrogen and hybrid vehicles.
In order to put the figures showing gasoline use in context, the committee can plot the projections from the Energy Information Administration (EIA, 2003) of U.S. oil consumption, production, and imports along with the committee’s estimates of gasoline consumption in the three cases. This superposition of the gasoline consumption estimates with the EIA projections of oil supply, demand, and imports appears in Figure 6-5. This figure shows that automotive consumption of gasoline is a large fraction of total oil consumption but is less than 50 percent of total U.S. use of crude oil and petroleum products. Thus, a transition to hydrogen in light-duty vehicles could lead to a large reduction in oil imports, although the United States would continue to import crude oil or petroleum products to be used in large trucks, airplanes, and other industrial uses.
It should be noted that none of the estimates in Figures 6-1 through 6-5 depends on which technologies are used to produce hydrogen, but rather on whether hydrogen vehicles are introduced into the marketplace and on the rate at which they are adopted. However, the environmental, energy security, economic, and domestic resource use implications depend significantly on which technologies are used to generate the hydrogen. These issues are examined in subsequent sections of this chapter.
As noted in Chapter 5, one of the important goals of the hydrogen program is to reduce the emissions of carbon dioxide into the atmosphere, given the impacts of possible global climate change associated with releases of greenhouse gases. Therefore, it is important to estimate the amount by which shifts from gasoline in automobiles to hydrogen for fueling vehicles would change CO2 emissions. In order to put the committee’s estimates in context, Figure 6-6 shows EIA projections of U.S. carbon emissions in the form of CO2, broken down by energy-consuming sectors and by fossil fuels. The EIA projects that by the year 2025, the United States will be emitting more than 2200 million metric tons of carbon, over