Ground-level ozone causes human respiratory problems and damages many plants but does nothing to increase ozone concentration in the stratosphere that protects the earth from the sun's ultraviolet radiation. There are many compounds that react with sunlight to form ground-level ozone, which, in combination with moisture and particulate matter, creates 'smog', the most visible form of air pollution. These compounds include carbon monoxide, unburned hydrocarbons, benzene, and nitrogen oxides (nitrous oxide and nitric oxide). According to Environment Canada (1998), the benefit of reducing smog has been estimated at a level of at least $10 billion each year. Ethanol use in low-level blends with gasoline results in an overall decrease in ozone formation.
In an effort to reduce automobile emissions that contribute to the formation of ground-level ozone, the highly populated state of California has legislated stringent automobile emissions standards. It has turned towards oxygenated fuels as one method of addressing the issue. Several Canadian urban centres record similar hazardous exposures to carbon monoxide, especially during late fall and winter, and would be out of compliance if Canada implemented air quality legislation equivalent to the U.S. Clean Air Act. In Canada, southern Ontario, southern British Columbia, and parts of Nova Scotia and New Brunswick are prone to smog.
The emissions produced by burning ethanol are less reactive with sunlight than those produced by burning gasoline, resulting in a lower potential for ground-level ozone formation. In Canada, where the volatility of ethanol blends must match normal gasoline, the ozone forming potential of ethanol blends is even lower than in the U.S., where ethanol blends are allowed to have increased volatility.
The 'Greenhouse Effect' refers to the Earth's atmosphere trapping the sun's radiation. It is a term often used synonymously with 'Global Warming', which refers to the increasing average global temperature, arising from an increase in greenhouse gases from industrial and transportation activities and population growth. Greenhouse gases contributing to the Greenhouse Effect include carbon dioxide, methane, and nitrous oxides.
Under current conditions, use of ethanol-blended fuels as E85 (85% ethanol
and 15% gasoline) can reduce the net emissions of greenhouse gases by as much as 37.1%. Ethanol-blended fuel as
E10 (10% ethanol and 90% gasoline) reduces greenhouse gases by up to 3.9%. These blends are available at 1,000
retail stations across Canada. By the year 2010, the reductions for E85 and E10 are projected to be 44.5% and 4.6%,
respectively. This represents about 1% of the total greenhouse gas reduction required to meet Canada's commitment
to the Kyoto Protocol (Levelton Engineering Ltd. and (S&T)2 Consulting Inc., 1999). It is expected that once ethanol is made from cellulose,
the greenhouse gas emissions reductions will further improve.
Carbon Monoxide (CO)
Use of a 10% ethanol blend results in a 25-30% reduction in carbon monoxide emissions by promoting a more complete combustion of the fuel.
Carbon Dioxide (CO2)
Use of ethanol can reduce net carbon dioxide (CO2) emissions by up to 100%, on a full life-cycle basis. Use of 10% ethanol-blended fuels results in a 6-10% reduction in net CO2. The carbon dioxide released from ethanol production activities and inputs, and its use, is less than that absorbed by the plants used to produce ethanol and the soil organic matter. The carbon dioxide produced during ethanol production and gasoline combustion is extracted from the atmosphere by plants for starch and sugar formation during photosynthesis. It is assimilated by the crop in its roots, stalks and leaves, which usually return to the soil to maintain organic matter, or to the grain, the portion currently used to produce ethanol. Over time, the organic matter breaks down to carbon dioxide, but with the implementation of soil conservation measures, such as reduced tillage, the soil organic matter will build up. Therefore, by increasing its organic matter content, the soil acts as a significant sink for carbon dioxide.
Nitrogen Oxides (NOx)
There is little difference in the amount of emissions of nitrogen oxides from ethanol-blended fuels in relation to conventional fuels. Reports cite this difference in the range of a 5% decrease to a 5% increase for low-level ethanol blends. For ethanol blends in the range of 85-95%, the reduction in emissions of nitrogen oxides may be of the magnitude of 20%.
Agricultural grain production for ethanol may generate a slight increase in nitrous oxide (N2O) emissions resulting from heavy fertilizer use. However, research and advances in agricultural technology in grain production is resulting in a reduction of these emissions, often to levels below other common crops.
The net effect of ethanol use still results in an overall decrease in ozone formation, since the significant reduction in carbon monoxide emissions compensates for any slight increase in NOx.
Volatile Organic Compounds (VOC's)
Volatile organic compounds are highly reactive in the atmosphere, and are significant sources of ground-level ozone formation. Because ethanol oxygenates the fuel, there is approximately a 7% overall decrease in exhaust VOC's emitted from low-level ethanol-blended fuels in relation to conventional fossil fuels. In high level blends, the potential for exhaust VOC reduction is 30% or more.
There is insufficient Canadian data on the emissions of evaporative VOCs. In Canada, where the volatility of ethanol blends must match normal gasoline, the VOCs emitted should be less than in the U.S., where ethanol blends are allowed to have increased volatility. Due to these Canadian regulations, the evaporative emissions of VOC's from ethanol blends are approximately equal to those from conventional gasoline. Although there is no existing Canadian data, it seems logical that in high-level ethanol blends, due to a lower vapour pressure, there is a reduction in evaporative VOC emissions.
Sulphur Dioxide (SO2) and Particulates
Neither sulphur dioxide nor particulate matter emissions are considered of significance in gasoline-powered engines. Nevertheless, Environment Canada is encouraging lower sulphur levels in gasoline, since sulphur can adversely affect the performance of emission-reducing catalytic converters. As ethanol contains no sulphur, and because it promotes more complete fuel combustion, blending gasoline with ethanol would reduce any potential for these emissions and the adverse effects of sulphur. In diesel engines, where SO2 and particulates are of concern, the use of ethanol-blended diesel or neat ethanol shows a significant reduction in these emissions.
Aldehydes have been associated with health risks. All oxygenates, including ethanol, emit higher levels of aldehydes than non-oxygenated gasoline. However, the Royal Society of Canada has determined that the risks associated with increased aldehyde emissions from ethanol-blended fuels are negligible, as the real quantity of emissions is quite small relative to other hazardous emissions, and are efficiently removed by the catalytic converter in a car.
Ethanol as an Octane-Enhancer
Benzene and Butadiene
Ethanol, as an octane enhancer, can substitute for benzene and other aromatic hydrocarbons, such as toluene, xylene, and other 'benzene-ring'-based compounds in gasoline. This substitution reduces emissions of benzene and butadiene, both of which are carcinogenic.
An overview of the emissions reductions from low-level and high-level ethanol blends is as follows :
|Emission||Low-level Blends (i.e., E10)||High-level Blends (i.e., E85)|
|Carbon Monoxide (CO)||25-30% decrease||25-30% decrease|
|Carbon Dioxide (CO2)||10% decrease||Up to 100% decrease (E100)|
|Nitrogen Oxides (NOx)||5% increase or decrease||Up to 20% decrease|
|Volatile Organic Carbons (VOC's):
No change (in Canada)
|30% or more decrease
|Sulphur Dioxide (SO2) and Particulate Matter||Decrease||Significant decrease|
|Aldehydes||30-50% increase (but negligible due to catalytic converter)||Insufficient data|
|Aromatics (Benzene and Butadiene)||Decrease||More than 50% decrease|
The environmentally beneficial attributes of ethanol-blended gasoline have resulted in its designation as an "Environmental ChoiceTM" product by the Canadian General Standards Board, and it is therefore eligible to have the "EcoLogoTM" displayed at licensed retail outlets.
Greening the Fleet
'FleetWise' is a federal initiative to address the pollution caused by vehicle emissions and its effect on climate change. It involves a gradual phased-in increase in use of alternative fuels, such as ethanol. The Government of Canada has committed to integrating environmental considerations and sound management practices in the operation of its motor vehicles. This includes a phased-in acquisition of alternative fuel vehicles by the year 2005.
Where to Get More Information
Canadian Renewable Fuels Association
90 Woodlawn Rd. W.
Guelph, Ontario N1H 1B2