FIGURE 6.19 Gasoline consumption for Case 2 and for the reference case.

FIGURE 6.20 Greenhouse gas emissions for Case 2 and for the reference case.

miles a year saves 167 gallons of gasoline per year. If a car is kept 10 years and gasoline costs $2.5 per gallon, the present value of fuel savings amounts to $2,565 (assuming a 10 percent discount rate). This would be enough to pay for the difference in first cost between a conventional gasoline car and a hybrid, which is estimated to be $1,800-$2,500 per car (Kromer and Heywood, 2007).

Case 3: Biofuels

Case 3, Biofuels, considers an emphasis on biofuels in the transportation sector. Assumptions about the introduction of biofuels are summarized in Table 6.8. Annual production levels for various biofuels are plotted in Figure 6.21. The detailed assumptions are discussed in Chapter 4. For reference, the maximum practicable case, in the committee’s judgment, is 700 million dry tons of sustainable biomass available in 2050, with all of the biomass used for cellulosic ethanol production at 90 gallons per dry ton. This would total 63 billion gallons of ethanol per year in 2050, the amount assumed in Case 3.

The AEO 2007 reference case includes about 12 billion gallons of corn ethanol by 2030 plus an additional 3 billion gallons of cellulosic ethanol. The committee extended this to assume that in the reference case, cellulosic ethanol production reaches 9 billion gallons per year by 2050. The assumed biofuels use in the reference case is shown in Figure 6.5.

TABLE 6.8 Assumed Biofuel Use in Case 3

 

Corn Ethanol

Cellulosic Ethanol

Biobutanol

Biodiesel

F-T Diesel via Biomass Gasification

Production (billion gallons)

 

 

 

 

Timing of introduction similar to that for biomass H2, toward end of scenario time frame

• 2002

 

 

 

 

 

• 2006

2.5

 

 

 

 

• 2008

6

 

 

0.25

 

• 2010

8

1

 

 

 

• 2015

10

6

 

0.6 (2012)

 

• 2020

12 (max = 30% of expanded corn crop)

16

0.1

 

 

• 2025

 

28

0.6

1.5 (max = 30% of soy crop, limited by land)

 

• 2030

 

36

2.6

 

• 2035

12

44

4.0

 

• 2050

 

63

 

 

CO2 reduction (energy equivalent basis)

22% relative to gasoline

85% relative to gasoline

 

80% relative to regular diesel

 

Oil reduction (energy equivalent basis)a

1 gallon gasoline equivalent ethanol replaces 0.96 gallon oil

1 gallon gasoline equivalent ethanol replaces 0.93 gallon oil

 

1 gallon biodiesel replaces 0.95 gallon oil

 

aGasoline = 119,000 Btu/gal, ethanol = 80,000 Btu/gal, and biodiesel is equivalent to regular diesel.



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