"The Energy Information Agency (EIA) estimates that the United States presently imports 58% of its oil (petroleum) and that this will grow to about 68% by 2030.This fact, combined with the recent escalation in world oil prices, has led to renewed interest in alternative fuels that might reduce or eliminate the growing dependence on foreign oil sources. Of particular concern are the applications that power the U.S. transportation system. […] It can be seen from table 1 that about 65% (13.4 million barrels per day) of U.S. oil consumption relates to transportation fuels. This number is somewhat misleading in that the energy conversion efficiency of the typical transportation plant is about 18% (see figure A1 of appendix A). Thus, the energy that is actually needed for transportation propulsion is equivalent to about 2.4 million barrels of oil per day (BPD). The remaining 11 million BPD emerges mostly as waste heat due to the underlying efficiency of the energy conversion process. In this paper we will use 13.4 million BPD as the goal that alternative fuels must meet. However, it should be kept in mind that a radical improvement in the energy efficiency of propulsion power plants would markedly change the transportation fuels requirement. The Department of Defense (DOD) is especially dependent on petroleum."
Center for Technology and National Security Policy: http://www.ndu.edu/CTNSP/