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

VIII. What Are The Impacts Of Increased Ethanol Use On Emissions And Air
Quality?
In this section, we evaluate the impact of increased production and use of
renewable fuels on emissions and air quality in the U.S., particularly ethanol and
biodiesel. In performing these analyses, we compare the emissions which would have
occurred in the future if fuel quality had remained unchanged from pre-Act levels to
those which will be required under the Energy Policy Act of 2005 (Energy Act or the
Act). This approach differs from that traditionally taken in EPA regulatory impact
analyses. Traditionally, we would have compared future emissions with and without the
requirement of the Energy Act. However, as described in Section VI, we expect that total
renewable fuel use in the U.S. in 2012 to exceed 7.5 billion gallons even in the absence of
the RFS program. Thus, a traditional regulatory impact analysis would have shown no
impact on emissions or air quality.
Strictly speaking, if the same volume and types of renewable fuels are produced
and used with and without the RFS program, the RFS program is having no impact on
emissions or air quality. However, levels of renewable fuel use are increasing
dramatically relative to both today and the recent past, with corresponding impacts on
emissions and air quality. We believe that it is appropriate to evaluate these changes
here, regardless of whether they are occurring due to economic forces or Energy Act
requirements.
In the process of estimating the impact of increased renewable fuel use, we also
include the impact of reduced use of MTBE in gasoline. It is the increased production
and use of ethanol which is facilitating the removal of MTBE while still producing the
required volume of RFG which meets both commercial and EPA regulatory
specifications. Because of this connection, we found it impractical to isolate the impact
of increased ethanol use from the removal of MTBE.
A. Effect of Renewable Fuel Use on Emissions
1. Emissions from Gasoline Fueled Motor Vehicles And Equipment
Several models of the impact of gasoline quality on motor vehicle emissions have
been developed since the early 1990’s. We evaluated these models and selected those
which were based on the most comprehensive set of emissions data and developed using
the most advanced statistical tools for this analysis. Still, as will be described below,
significant uncertainty still exists as to the effect of these gasoline components on
emissions from both motor vehicle and nonroad equipment, particularly from the latest
models equipped with the most advanced emission controls. Pending adequate funding,
we plan to conduct significant vehicle and equipment testing over the next several years
to improve our estimates of the impact of these additives and other gasoline properties on
emissions. The results of this testing will not be available for inclusion in the analyses
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