The long awaited report from the
National Academy of Sciences regarding ethanol's impact on ozone formation has
been released, and the report demonstrates ethanol's positive impact on carbon
monoxide and toxics in high-emitting vehicles. The report, "The
Ozone-Forming Potential of Reformulated Gasoline," was completed by the National
Academy of Science for the National Research Council.
The Council's report confirmed the importance of carbon
monoxide in the formation of urban ozone, concluding that more than 20
percent of vehicle-related ozone pollution comes from carbon monoxide. The
Council also notes that carbon monoxide emissions will play an even larger role
in ozone formation as volatile organic compound emissions from vehicles continue
to decrease. California Air Resources Board data demonstrates that carbon
monoxide reductions from ethanol-blended fuels is twice that of
MTBE-blends.
The report also acknowledges ethanol's ability to reduce toxic
emissions, one of the most important benefits of the reformulated gasoline
program.
The Council recognizes that a majority of ozone-precursor emissions
are produced from a relatively small number of high-emitting vehicles, and
states that "the use of oxygenated fuels in those vehicles will be of the
greatest benefit by reducing the exhaust emissions of carbon monoxide and
volatile organic compounds by approximately 20 percent."
While the Council's
report concluded that the increase in evaporative emissions from ethanol-blends
exceeds the benefits of reduced exhaust volatile organic compound and carbon
monoxide emissions from ethanol's increased oxygen content, the Council did
concede that this determination was based on the results of a test of only six
normal emitting vehicles. The report notes that including high-emitting
vehicles might demonstrate additional offsetting benefits from ethanol.
The report concludes that there are air quality benefits
from the use of reformulated gasoline due to the fuel's reduced sulfur, olefin
and aromatic content levels. Importantly, it is the addition of oxygenates
such as ethanol that allow refiners to reduce these components to the levels
that are providing air quality benefits, a point not made by the Council's
report.
