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

Equivalence Values should also account for the renewable content of renewable
fuels, since the presence of any non-renewable content impairs the ability of the
renewable fuel to replace or reduce the quantity of fossil fuel present in a fuel mixture
used to operate a motor vehicle. The Act specifically states that only the renewable fuel
portion of a blending component should be considered part of the applicable volume
under the RFS program. We have interpreted this to mean that every renewable fuel
should be evaluated at the molecular level to distinguish between those components that
were derived from a renewable feedstock, versus those components that were derived
from a fossil fuel feedstock. Along with energy content in comparison to ethanol, the
relative amount of renewable versus non-renewable content can then be used directly as
the basis for the Equivalence Value.
We propose that the calculation of Equivalence Values should simultaneously
take into account both the renewable content of a renewable fuel and its energy content in
comparison to ethanol. To accomplish this, we propose the following formula:
EV = (RRF / REth) x (ECRF / ECEth)
EV = Equivalence Value for the renewable fuel
RRF = Renewable content of the renewable fuel, in percent
REth = Renewable content of ethanol, in percent
ECRF = Energy content of the renewable fuel, in Btu per gallon (LHV)
ECEth = Energy content of ethanol, in Btu per gallon (LHV)
R is a measure of that portion of a single renewable fuel molecule which can be
considered to have come from a renewable source. Since R is being combined with
relative energy content in the formula above, the value of R cannot be based on the
weight fraction of the renewable atoms in the molecule, but rather must be based on the
energy content of those atoms. As a result the calculation of R for any particular
renewable fuel requires an analysis of the chemical process through which it was
produced. A detailed explanation of calculations for R and several examples are given in
a technical memorandum in the docket 19 .
In the case of ethanol, denaturants are added to preclude its use as food.
Denaturants are generally a fossil-fuel based, gasoline-like hydrocarbon in concentrations
of 2 - 5 volume percent, with 5 percent being the most common historical level. In
general this would mean that the Equivalence Value of ethanol would be 0.95. However,
we believe that the Equivalence Value for ethanol should be specified as 1.0 despite the
presence of a denaturant. First, as stated above, ethanol is expected to dominate the
renewable fuel pool for at least the next several years, and it is likely that the authors of
the Act recognized this fact. Thus it seems likely that it was the intent of the authors of
the Act that each physical gallon of denatured ethanol be counted as one gallon for RFS
compliance purposes. Second, the accounting of ethanol has historically ignored the
19 "Calculation of equivalence values for renewable fuels under the RFS program", memo from David
Korotney to EPA Air Docket OAR-2005-0161
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