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ETHANOL
& THE ENVIRONMENT
Transportation
Fuels: America’s Biggest Polluter
If we’re going to clean up America’s air, we need to start
with its biggest polluter—engine emissions.
The U.S. Department
of Energy estimates that 82 percent of the carbon monoxide, 43 percent
of the reactive organic gases (precursors to ground level ozone) and
57 percent of the nitrogen oxides in U.S cities are emitted from petroleum-based
transportation fuels.
The U.S. Environmental
Protection Agency (EPA) says that gasoline is the largest source of
manmade carcinogens. The American Lung Association has noted that transportation
sources are responsible for 55.8 percent of outdoor air pollution—including
77.3 percent of total carbon monoxide. The burning of fossil fuels also
contributes to the development of greenhouse gases.
How
Ethanol Reduces Emissions
Ethanol adds oxygen to gasoline—helping it burn more completely,
thus significantly reducing tailpipe emissions. Ethanol is a clean-burning
renewable fuel that helps reduce emissions of carbon monoxide (CO) and
smog-forming volatile organic compounds (VOC).
Studies have shown
that ethanol:
- Reduces tailpipe
carbon monoxide emissions by as much as 30 percent
- Reduces exhaust
VOC emissions by 12 percent
- Reduces toxic
emissions by 30 percent
- Reduces particulate
matter (PM) emissions by more than 25 percent. (Particulate matter
has been found to penetrate deeply into human lungs.)
The American Lung
Association of Metropolitan Chicago credits ethanol-blended reformulated
gasoline with reducing smog-forming emissions by 25 percent since 1990.
While ethanol increases
the tendency of fuel to evaporate in warm weather (volatility), the
total emissions from gasoline evaporation are regulated in areas where
air quality is of concern during the summer. Therefore, refiners are
responsible by law for managing the components in gasoline so as not
to exceed those limits—and they do so by reducing levels of volatility
of gasoline.
Gasoline is a complex
mixture of dozens of chemicals, many of them toxic such as benzene.
When ethanol is added to gasoline, the potency of these toxic additives
is diluted.
A 1999 study of
the impact of ethanol on air quality by the California Environmental
Policy Committee concluded that ethanol in gasoline resulted in slightly
higher levels of acetaldehyde and peroxyacetyl nitrate (PAN). However,
the study also concluded that these slight increases were more than
offset by reductions in formaldehyde, a toxic substance considerably
more harmful than acetaldehyde.
This study also
noted that “other components of gasoline, such as aromatic compounds
and olefins, are primarily responsible for the formation of formaldehyde,
acetaldehyde and PAN due both to their greater abundance in gasoline
and their shorter atmospheric lifetimes.”
The
Elimination of MTBE
Methyl tertiary butyl ether (MTBE) is a fuel oxygenate derived from
petroleum. MTBE has been used extensively in the nation’s gasoline
supply and has been a chief competitor of ethanol in the oxygenate market.
But MTBE has some
serious problems. It has been proven to pollute groundwater resources.
At certain concentrations, drinking water contaminated with MTBE has
a foul taste or odor. MTBE has also been listed as a possible carcinogen
for humans. These concerns have caused 20 states to pass legislation
either banning the use of MTBE or leading to its removal.
The elimination
of MTBE from the nation’s fuel supply will create increased demand
for ethanol as an oxygenate. If ethanol replaced all of the MTBE being
sold—and all conventional markets for ethanol-blended gasoline
were maintained—the annual demand for ethanol would increase by
some 3.6 billion gallons.
Ethanol
is Safe in Soil and Groundwater
Ethanol is non-toxic, water soluble and is the most harmless and biodegradable
component of gasoline. In fact, ethanol occurs naturally during the
fermentation of organic matter.
When gasoline is
spilled on land or in water, ethanol is the first component to quickly,
safely and naturally degrade. More important, the presence of ethanol
in gasoline means the reduced presence of other more toxic components
such as benzene—so gasoline spills are less threatening to the
environment.
Last
reviewed June 10, 2005
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