TABLE 7-2 Relative Categories of GHG Emissions in 2005 and 2030 for Major Categories of Light-Duty-Vehicle Fuels and Technologies

Category of Aggregate CO2-eq Emission Estimates (g/VMT)

2005

2030

150–250

E85 herbaceous

E85 corn stover

E85 herbaceous

E85 corn stover

250–350

Hydrogen gaseous

E85 corn

Diesel with biodiesel

Hydrogen gaseous

CNG

350–500

E85 corn

Diesel with biodiesel

Grid-independent HEV

Grid-dependent HEV

Electric vehicle

CNG

Grid-independent HEV

SI conventional gasoline, RFG

Grid-dependent HEV

Electric vehicle

Low-sulfur diesel

E10 herbaceous, corn stover

SIDI conventional gasoline

E10 corn

SI tar sands

>600

Tar sands

 

500–599

Conventional gasoline and RFG

E10

Low-sulfur diesel

 

ABBREVIATIONS: CO2-eq, carbon dioxide equivalent; VMT, vehicle miles traveled; E85, ethanol 85% blend; E10, ethanol 10% blend; HEV, hybrid electric vehicle; CNG, com pressed natural gas; RFG, reformulated gasoline; SI, spark ignition; SIDI, spark ignition direct injection.

  • The tar-sands-based fuels have the highest GHG emissions of any of the fuels that the committee considered.

As shown in Figure 7-7, and in contrast to the damages analysis above, the operation of the vehicle is in most cases a substantial relative contributor to total life-cycle GHG emissions. That is not the case, however, with either the grid-dependent technologies (for example, electric or grid-dependent hybrid) or the hydrogen fuel-cell vehicles. In the latter vehicle technologies, the dominant contributor to life-cycle GHG emissions is electricity generation and the production of hydrogen rather than vehicle operation.

Heavy-Duty Vehicles

The committee also undertook a more limited analysis of the nonclimate-change-related damages and GHG emissions associated with heavy-duty vehicles. Although this analysis included operation, feedstock, and fuel com-



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