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

1. Primary Analysis
The national emission inventories for VOC, CO and NOx in 2012 with current
fuels (i.e., “reference fuel”) are summarized in Table VIII.B.1-1. Also shown are the
changes in emissions projected for the two levels of ethanol use (i.e., “control cases”)
described in Section VI and the two different cases for ethanol use in RFG.
Table VIII.B.1-1
2012 Emissions Nationwide from Gasoline Vehicles and Equipment under Several
Ethanol Use Scenarios – Primary Analysis (tons per year)
Inventory Change in Inventory in Control Cases
7.2 Billion gallons of 9.6 Billion gallons of
Pollutant Reference
ethanol
ethanol
Case Minimum Maximum Minimum Maximum
RFG Use RFG Use RFG Use RFG Use
VOC 5,837,000 31,000 8,000 57,000 29,000
NOx 2,576,000 19,000 20,000 40,000 39,000
CO 64,799,000 -843,000 -1,229,000 -1,971,000 -2,319,000
Benzene 177,000 -6,000 -3,000 -11,000 -8,000
Formaldehyde 40,200 300 0 800 500
Acetaldehyde 19,800 6,200 5,000 9,600 8,500
1,3-Butadiene 18,200 -500 -300 -800 -600
Both VOC and NOx emissions are projected to increase with increased use of
ethanol. However, the increases are small, generally less than 2 percent. Emissions of
formaldehyde are also projected to increase slightly, on the order of 1-3 percent.
Emissions of 1,3-butadiene and CO are projected to decrease by about 1-4 percent.
Benzene emissions are projected to decrease by 2-6 percent. The largest change is in
acetaldehyde emissions, an increase of 25-48 percent, as acetaldehyde is a partial
combustion product of ethanol.
CO also participates in forming ozone, much like VOCs. Generally, CO is 15-50
times less reactive than typical VOC. Still, the reduction in CO emissions is roughly 20-
140 times the increase in VOC emissions in the four scenarios. Thus, the projected
reduction in CO emissions is important from an ozone perspective. However, as
described above, the methodology for projecting the effect of ethanol use on CO
emissions is inconsistent with that for exhaust VOC and NOx emissions. Thus,
comparisons between changes in VOC and CO emissions are particularly uncertain.
In addition to these changes in emissions due to ethanol use, biodiesel use is
expected to have a minor impact on diesel emissions. Table VIII.B.1-2 shows the
expected emission reductions associated with an increase in biodiesel fuel use from the
reference case of 28 million gallons in 2012 to approximately 300 million gallons per
year in 2012. This represents an increase from 0.06 to 0.6 percent of onroad diesel fuel
consumption. In terms of a 20 percent biodiesel blend (B20), it represents an increase
from 0.3 to 3.2 percent of onroad diesel fuel consumption.
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