The committee also notes that additional benefits may accrue (e.g., public health benefits from reduction in air pollution) from this transition; such other benefits are discussed briefly in this chapter. However, the two primary benefits above, called out in the statement of task, were the focus of the committee’s effort.

Reduced Oil Consumption

It is difficult for the U.S. oil industry to increase domestic oil production due to declining production from existing oil fields, environmentally restricted acreage, and the complexity of new exploration and production projects, especially offshore. Therefore any significant reduction of imports probably would require a concomitant reduction in demand for oil. Reduction of oil imports offers two main benefits to the United States:

  1. Improved energy security, at least to the extent that reduced oil imports are accompanied by the development and adoption of a more diverse set of indigenous energy sources for U.S. transportation, such as coal, nuclear power, biofuels, or other renewable resources; and

  2. Potential for long-term reduction of the outflow of dollars currently required to pay for the nation’s energy needs, especially as indigenous sources of energy are eventually exploited to produce hydrogen. It is also possible that decreased pressure on world oil markets may contribute to a reduction in the price of the oil that must still be imported.

The U.S. transportation sector consumed 28 quadrillion British thermal units (Btu) (28 quads) of energy in 2006, representing 28 percent of total energy consumed. Furthermore, 96 percent of the energy used in the transportation sector was consumed in the form of petroleum products (DOE-EIA, 2007, Tables 2.1a and 2.1e). Furthermore, in 2006, about two-thirds of the crude oil used in the United States was imported (12.3 million barrels per day out of a total of 20.6 million barrels per day, or approximately 60 percent), a proportion that has grown steadily since the early 1980s (DOE-EIA, 2007, Diagram 2 and Figure 5.1).

As shown in Figure 6.32 in Chapter 6, the alternative approaches studied by the committee (internal combustion engine [ICE] improvements and biofuels) offer significant reductions in oil consumption by 2020, but HFCVs are on the path to achieve much more significant savings in the 2035-2050 time frame, at a time when the rate of improvement in oil import reduction due to biofuels and ICE improvements would be slowing.

A further benefit (although not unique) of the use of hydrogen as a transportation fuel is the multiplicity of fuel resources and production methods from which hydrogen can be made, including distributed and central-station steam methane reformers (SMRs) used to convert natural gas to hydrogen, coal gasification, biomass gasification, and electrolysis of water (using grid electricity, renewable energy, or nuclear power; see Table 6.1). Although those fuels and pathways that rely more heavily on indigenous U.S. energy resources (e.g., coal gasification, biomass gasification, and water electrolysis with renewable or nuclear power) today require additional development, all represent alternatives that might be able to mitigate the impact of a significant disruption in the availability of crude oil or natural gas imports.

Reductions in CO2Emissions

As shown in Figure 6.33, the alternative technologies reviewed by the committee—(1) evolutionary efficiency improvements to vehicles with internal combustion engines and (2) biofuels—have the potential to achieve significant reductions in greenhouse gas emissions by 2020. The former has been incorporated in the reference case until 2020 and could continue to improve efficiency thereafter. However, one can also see in Figure 6.33 that growth in the benefits from these alternative technologies could slow significantly in subsequent years under the scenarios used in this study, while the benefits from adoption of HFCVs, whose numbers begin to be significant in the 2020-2025 time frame, are on a path to increase rapidly throughout 2035-2050 under the maximum practicable scenario. Although it is difficult to predict many years into the future, the sense of the committee is that these trends seem reasonable: the impact of biofuels in the United States is limited by available land and water, and improvements to ICE vehicles are limited by considerations such as cost, how much more efficient engines can be while still meeting durability and environmental requirements, and how much weight can be removed from the vehicle while still meeting consumer preferences. During that same period, the benefits from HFCVs have the potential to continue growing, due both to technology improvements in these relatively new systems and to increasing market penetration. Thus, a transition to HFCVs offers the potential, if successful, to eventually achieve benefits exceeding those of the alternative technologies.

Finally, it should be noted that simply transitioning to hydrogen fuel cell vehicles will not necessarily result in the magnitude of CO2 reductions shown here. Those reductions will depend on the pathways via which hydrogen is produced, as well as on the higher efficiency of HFCVs relative to conventional gasoline engines. As noted in Chapter 6, during the transition period when hydrogen is assumed to be produced via reforming of natural gas, the life-cycle greenhouse gas emissions of HFCVs are still lower than those of conventional vehicles, thanks largely to the much higher efficiency of fuel cells. In the longer term, after about 2025, hydrogen is assumed to be supplied increasingly from central coal-based plants with carbon capture and sequestration (CCS). As noted in earlier chapters of this report, strong policy drivers limiting CO2 emissions will be required to implement CCS at central coal plants. To the extent that CCS



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement