FIGURE 2.11 Estimates of the potential cellulosic ethanol supply in 2020 and 2035 (relative to 2007) compared to total liquid fuel consumption. The current (2007) U.S. liquid fuel consumption, in barrels of oil, for transportation is shown on the left (in green). To estimate supply, an accelerated deployment of technologies (as described in Part 2 of this report) and the availability of 500 million dry tonnes per year of cellulosic biomass for fuel production are assumed after 2020. Potential liquid fuel supplies are estimated individually for each technology, and estimates do not account for future fuel demand, competition for biomass, or competition among supply sources. Potential supplies are expressed in barrels of gasoline equivalent. One barrel of oil produces about 0.85 barrels of gasoline equivalent of gasoline and diesel. All values have been rounded to two significant figures.

FIGURE 2.11 Estimates of the potential cellulosic ethanol supply in 2020 and 2035 (relative to 2007) compared to total liquid fuel consumption. The current (2007) U.S. liquid fuel consumption, in barrels of oil, for transportation is shown on the left (in green). To estimate supply, an accelerated deployment of technologies (as described in Part 2 of this report) and the availability of 500 million dry tonnes per year of cellulosic biomass for fuel production are assumed after 2020. Potential liquid fuel supplies are estimated individually for each technology, and estimates do not account for future fuel demand, competition for biomass, or competition among supply sources. Potential supplies are expressed in barrels of gasoline equivalent. One barrel of oil produces about 0.85 barrels of gasoline equivalent of gasoline and diesel. All values have been rounded to two significant figures.

Sources: Data from Energy Information Administration (2008) and Chapter 5 in Part 2 of this report.

opment of domestic resources will be essential to help prevent increases in U.S. import dependence.

Substituting other domestically produced liquid fuels could further reduce petroleum imports. Ethanol is already being made from corn grain in commercial quantities in the United States, but corn ethanol is likely to serve only as a transition fuel to more sustainable biofuels production, given the social and environmental concerns about using corn for fuel. The most promising substitutes before 2020 are cellulosic ethanol (Figure 2.11) and fuels produced from coal (coal-to-liquid fuels; Figure 2.12) and mixtures of coal and biomass (biomass-and-coal-to-



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