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

assuming only that blending of ethanol into summertime RFG cause butanes to be
removed.
For estimating the volume of butane which must be removed from the gasoline
because of the addition of ethanol, we assumed that ethanol will be used at 10 volume
percent except for California where it would continue to be used at 5.7 volume percent.
Development of the estimates for winter vs. summer ethanol consumption for the control
cases is discussed in Chapter 2.1 of the RIA. For the reference case we estimated that 55
percent of the ethanol would be used in the winter and 45 percent in the summer. Table
VII.C.4-1 summarizes the summertime RFG and wintertime RFG and CG volumes of
ethanol and estimated change in butane content.
Table VII.C.4-1
Estimated Changes in U.S. Summertime RFG Ethanol Volumes and their Impact on
Butane Blending into Gasoline (million gallons in 2012)
Reference 7.2 Bil Gals 7.2 Bil Gals 9.6 Bil Gals 9.6 Bil Gals
Case Max RFG Min RFG Max RFG Min RFG
Summertime RFG
Ethanol
1,155 1,932 244 1,932 244
Wintertime RFG
& CG Ethanol
2,178 3,999 4,812 5,303 6,132
Change in Butane -140 to -456 164 to -297 -140 to -690 164 to -535
The change in volume of ethanol, MTBE, alkylate, and butane for each control
case is adjusted for energy content. The volume of refinery gasoline is then adjusted to
maintain the same energy content as that of the reference gasoline pool. The refinery
gasoline production is estimated by dividing the BTU content of gasoline, estimated to be
115,000 BTU per gallon, into the total amount of BTUs for the entire gasoline pool after
accounting for the BTUs of the other blendstocks. The BTU-balanced gasoline pool
volumes for each control case are shown in Table VII.C.4-2. The changes are shown for
both assumptions with respect to the need to remove butane from winter gasoline to
accommodate more ethanol blending.
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