Regulation of Fuels and Fuel Additives: Renewable Fuel Standard ...
Regulation of Fuels and Fuel Additives: Renewable Fuel Standard ...
Regulation of Fuels and Fuel Additives: Renewable Fuel Standard ...
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<strong>of</strong> their more approximate nature. Their geographical concentration also makes it more<br />
difficult to simulate with the Ozone RSM.<br />
The Ozone RSM was created using multiple runs <strong>of</strong> the Comprehensive Air<br />
Quality Model with Extensions (CAMx). Base <strong>and</strong> proposed control CAMx<br />
metamodeling was completed for the year 2015 over a modeling domain that includes all<br />
or part <strong>of</strong> 37 Eastern U.S. states, plus the District <strong>of</strong> Columbia. For more information on<br />
the Ozone RSM, please see the Chapter 5 <strong>of</strong> the DRIA for this proposal.<br />
The Ozone RSM limits the number <strong>of</strong> geographically distinct changes in VOC<br />
<strong>and</strong> NOx emissions which can be simulated. As a result, we could not apply distinct<br />
changes in emissions for each county. Therefore, two separate runs were made with<br />
different VOC <strong>and</strong> NOx emissions reductions. We then selected the ozone impacts from<br />
the various runs which best matched the VOC <strong>and</strong> NOx emission reductions for that<br />
county. This models the impact <strong>of</strong> local emissions reasonably well, but loses some<br />
accuracy with respect to ozone transport. No ozone impact was assumed for areas which<br />
did not experience a significant change in ethanol use. The predicted ozone impacts <strong>of</strong><br />
increased ethanol use for those areas where ethanol use is projected to change by more<br />
than a 50% market share are summarized in Table VIII.C.1-1. As shown in the Table<br />
5.1-2 <strong>of</strong> the DRIA, national average impacts (based on the 37-state area modeled) which<br />
include those areas where no change in ethanol use is occurring are considerably smaller.<br />
Table VIII.C.1-1<br />
Impact on 8-hour Design Value Equivalent Ozone Levels (ppb) a<br />
Primary Analysis Sensitivity Analysis<br />
Min RFG Use Max RFG Use Min RFG Use Max RFG Use<br />
Minimum Change -0.030 -0.025 -0.180 0.000<br />
Maximum Change 0.395 0.526 0.637 0.625<br />
Average Change b<br />
0.137 0.171 0.294 0.318<br />
Population-<br />
0.134 0.129 0.268 0.250<br />
Weighted Change b<br />
a In comparison to the 80 ppb 8-hour ozone st<strong>and</strong>ards<br />
b Only for those areas experiencing a change in ethanol blend market share <strong>of</strong> at least 50 percent.<br />
As can be seen, ozone levels generally increase to a small degree with increased<br />
ethanol use. This is likely due to the projected increases in both VOC <strong>and</strong> NOx<br />
emissions. Some areas do see a small decrease in ozone levels. In our primary analysis,<br />
where exhaust emissions from Tier 1 <strong>and</strong> later onroad vehicles are assumed to be<br />
unaffected by ethanol use, the population-weighted increase in ambient ozone levels in<br />
those areas where ethanol use changed significantly is 0.129-0.134 ppb. Since the 8-hour<br />
ambient ozone st<strong>and</strong>ard is 80 ppb, this increase represents about 0.16 percent <strong>of</strong> the<br />
st<strong>and</strong>ard, a very small percentage.<br />
In our sensitivity analysis, where exhaust emissions from Tier 1 <strong>and</strong> later onroad<br />
vehicles are assumed to respond to ethanol like Tier 0 vehicles, the population-weighted<br />
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