Regulation of Fuels and Fuel Additives: Renewable Fuel Standard ...

Table IX.B.3-1
Displacement indexes derived from GREET
Corn ethanol Cellulosic ethanol Biodiesel
DIPetroleum 92.3% 92.7% 84.6%
DIFossil Fuel 40.1% 96.0% 47.9%
DIGHG 25.8% 98.1% 53.4%
DICO2 43.9% 110.1% 56.8%
The displacement indexes in this table represent the impact of replacing a Btu of
gasoline or diesel with a Btu of renewable fuel. Thus, for instance, for every Btu of
gasoline which is replaced by corn ethanol, the total lifecycle GHG emissions that would
have been produced from that Btu of gasoline would be reduced by 25.8 percent. For
every Btu of diesel which is replaced by biodiesel, the total lifecycle petroleum energy
that would have been consumed as a result of burning that Btu of diesel fuel would be
reduced by 84.6 percent.
Note that our DI estimates for cellulosic ethanol assume that the ethanol in
question was in fact produced from a cellulosic feedstock, such as wood, corn stalks, or
switchgrass. However, the definition of cellulosic biomass ethanol given in the Energy
Act also includes ethanol made from non-cellulosic feedstocks if 90 percent of the
process energy used to operate the facility is derived from a renewable source. In the
context of our cost analysis, we have assumed this latter definition of cellulosic ethanol.
Further discussion of this issue can be found in Chapter 1, Section 1.2.2 of the RIA.
C. Impacts of Increased Renewable Fuel Use
We used the methodology described above to calculate impacts of increased use
of renewable fuels on consumption of petroleum and fossil fuels and also on emissions of
CO2 and GHGs. This section describes our results.
1. Fossil Fuels And Petroleum
We used the equation for S above to calculate the reduction associated with the
increased use of renewable fuels on lifecycle fossil fuels and petroleum. These values are
then compared to the total US transportation sector emissions to get a percent reduction.
The results are presented in Tables IX.C.1-1 and IX.C.1-2.
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