produced with petroleum. As noted under Finding 5, however, alternative liquid fuels can only substitute for a portion of petroleum use. Moreover, geologic storage of CO₂ from coal-to-liquid fuel and coal-and-biomass-to-liquid fuel production would have to be demonstrated to be safe and commercially viable by 2015 for these fuels to be produced in quantity starting around 2020.

Further reductions in greenhouse gas emissions from the transportation sector will have to be achieved through greater vehicle efficiency and, if greenhouse gas emissions from the electricity sector can be reduced, through electrification of the LDV fleet (as discussed under Finding 5). However, substantial reductions in emissions via these pathways are not likely to occur until late in the 2020–2035 period or beyond. As is the case for liquid fuel supply, the widespread deployment of electric or hydrogen fuel-cell vehicles between 2035 and 2050 holds some hope for more substantial long-term reductions in greenhouse gas emissions in the transportation sector, again depending on how the electricity and hydrogen are generated. As noted previously, the National Research Council (2008) estimated the potential reduction in petroleum use in 2050 from the deployment of hydrogen fuel-cell LDVs under the best-case scenario to be about 70 percent below the projected petroleum consumption of a fleet of comparable gasoline-fueled vehicles.

To enable accelerated deployments of new energy technologies starting around 2020, and to ensure that innovative ideas continue to be explored, the public and private sectors will need to perform extensive research, development, and demonstration over the next decade. Given the spectrum of uncertainties involved in the creation and deployment of new technologies, together with the differing technological needs and circumstances across the nation, a portfolio that supports a broad range of initiatives from basic research through demonstration will likely be more effective than targeted efforts to identify and select technology winners and losers.

As discussed in some detail in Part 2 of this report, the next decade offers opportunities to gain knowledge and early operating experience that in turn could enable widespread deployments of new energy-supply technologies beginning around 2020. These technology-development opportunities include: