. "6. Implications of a Transitionto Hydrogen in Vehicles for the U.S. Energy System." The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs. Washington, DC: The National Academies Press, 2004.
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The Hydrogen Economy: Opportunities, Costs, Barriers, and R&D Needs
Steam reforming using natural gas in a central station or distributed facility could reduce CO2 emissions on the order of 200 million metric tons per year by 2050, in either state of technology development. Also, sharp reductions in CO2 emissions would occur if all of the hydrogen was generated using biomass as a feedstock, or nuclear power as a heat source, or if the CO2 from a coal-based or a natural-gas-based technology was separated and sequestered.
At the other extreme, if all of the hydrogen could be generated using biomass as a feedstock and all of the CO2 could be separated at the point of hydrogen production and sequestered, there would be negative net emissions of CO2 into the atmosphere after 2036. That is, on net, the process would take significant amounts of CO2 out of the atmosphere.8
SOME ENERGY SECURITY IMPACTS OF THE COMMITTEE’S VISION
As noted, a second important goal of the hydrogen program is to improve energy security by substituting secure domestic resources for imported energy resources, particularly those that may be traded in unstable international markets. Figure 6-4 shows that a transition to hydrogen in light-duty vehicles could sharply reduce the use of gasoline and thus could reduce the importation of oil. Some of the technologies would use domestic resources without increasing the importation of other energy from potentially unstable parts of the world. Technologies based on coal, biomass, nuclear power, or entirely on renewables, such as wind turbines and photovoltaics, would not lead to significant energy imports. A transition to hydrogen could improve energy security if the hydrogen were generated from such domestic feedstocks.
Other technologies, however, would use natural gas, a commodity which, although produced domestically, is also imported in significant quantities and would be subject to some of the same international market instability that occurs in the petroleum markets. Additional uses of natural gas would lead to additional imports. In this case, whether energy security is improved or harmed depends on whether the security benefits from reduced oil imports are greater than the security costs of increased natural gas imports.
In order to examine this issue, estimates were developed of the amount of natural gas that would be used if all of the hydrogen were generated using one of the natural-gas-based technologies. These estimates appear in Figure 6-11, which includes estimates for both current and possible future technologies. This figure also includes the EIA projections of natural gas supply, demand, and imports in order to put the estimates from the committee’s vision in context.
Figure 6-11 shows that if all of the hydrogen were generated using one or more of the natural-gas-based technologies, the increase in natural gas consumption would be a significant fraction of the projected domestic production. It also shows that, according to EIA projections, the United States will be importing a significant fraction of this natural gas in the years 2010 through 2025. Given the magnitude of the use of natural gas for hydrogen production, it can be reasonably expected that most of the additional consumption will result in additional imports of natural gas once the United States gets beyond a transition period. However, during the transition period (through 2030), natural gas imports would not increase significantly.
The additional use of natural gas can be compared with the reduced use of gasoline. Figure 6-12 provides this comparison for the current technologies, and Figure 6-13 provides the comparison for possible future technologies. Both of these graphs plot, on the same scale, the gasoline reductions associated with the penetration of hydrogen vehicles in place of hybrid electric vehicles, and the natural gas use increases for the central station natural-gas-based technologies, with and without sequestration, and the distributed reforming of natural gas.
Figures 6-12 and 6-13 show that the increases in natural gas use, measured in quads, are of similar magnitude to the decreases in gasoline use, although the natural gas increases with the possible future technologies will be somewhat smaller than the decreases in gasoline use will be. These figures suggest that it is unlikely that a transition to hydrogen based on natural gas would significantly increase energy security.
It must be stressed, however, that the issue raised here would not be relevant for the other domestically produced resources or if large new sources of domestic natural gas are found. Technologies based on coal, biomass, nuclear power, or the two renewables—wind turbines and photovoltaics—would not result in such compensating increases of energy imports. A transition to hydrogen using these feedstocks could thus improve energy security.
A sharp reduction in gasoline use would require important adjustments in U.S. petroleum refining. These adjustments themselves could have energy security implications. Existing refineries swing between summer and winter differences in demand for gasoline and distillate fuels. However, if gasoline use is reduced to a very small portion of refined products, new refining processes may be needed. Alternatively, U.S. refiners might continue importing crude oil, making gasoline for exportation. The implications of such a scenario, or of alternative responses, are worthy of examination.
Less carbon is sequestered in the possible future biomass technology case than in the current technology case (i.e., carbon emissions become less negative). This reduction would be the result of the increased efficiency of hydrogen generation with the new technologies. A more efficient process implies that less biomass is needed per kilogram of hydrogen and thus less CO2 is removed from the atmosphere and fixed as organic carbon in the biomass.