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Ethanol (E85)
Benefits
Ethanol is a renewable, largely domestic transportation fuel. Whether used in low-level blends, such as E10 (10% ethanol, 90% gasoline), or in E85 (85% ethanol, 15% gasoline), ethanol helps reduce imported oil and greenhouse gas emissions. Its use also supports the U.S. agricultural sector.
Emissions
The carbon dioxide released when ethanol is burned is balanced by the carbon dioxide captured when the crops are grown to make ethanol. This differs from petroleum, which is made from plants that grew millions of years ago. According to Argonne National Laboratory, on a life-cycle analysis basis, corn-based ethanol production and use reduces greenhouse gas emissions (GHGs) by up to 52% compared to gasoline production and use. Cellulosic ethanol use could reduce GHGs by as much as 86%.
Ethanol has been blended in low levels (10% or less) with gasoline for many years. This use of ethanol as an "oxygenate" promotes more complete combustion of the fuel, which can reduce exhaust emissions of carbon monoxide—a regulated pollutant harmful to human health—by 20% to 30% compared with pure gasoline.
Flexible fuel vehicles (FFVs) fueled with E85 (85% ethanol, 15% gasoline) also emit less carbon monoxide than gasoline-powered vehicles. Emissions from E85-fueled FFVs of other regulated pollutants, such as hydrocarbons and nitrogen oxides (NOx), are similar to those from gasoline-powered vehicles.
In addition to exhaust emissions, all vehicles emit hydrocarbons due to evaporation of fuel from their tanks and fueling systems, especially in warm weather. The common oxygenate blend E10 (10% ethanol, 90% gasoline) has a higher vapor pressure than pure gasoline and thus produces higher evaporative emissions. E85's vapor pressure is lower than gasoline's, so it produces lower evaporative emissions.
Manufacturing
About two-thirds of U.S. petroleum demand is in the transportation sector. Sixty percent of U.S. petroleum is currently imported. Ethanol, on the other hand, is almost entirely produced from domestic crops today. Its use, and that of other alternative fuels, can displace a significant amount of imported petroleum.
Almost any plant-based material can be an ethanol feedstock. All plants contain sugars, and these sugars can be fermented to make ethanol in a process called biochemical conversion. Plant material also can be converted to ethanol using heat and chemicals in a process called thermochemical conversion. See Ethanol Production to learn more about these processes.
Some plants are easier to process into ethanol than others. Some require few resources to grow, while others need intensive care. Some are used for food as well as fuel, while others are cultivated exclusively for ethanol; even plant-based wastes can become ethanol. Climate and soil type determine the types and amounts of plants that can be grown in different geographic areas.
Another important consideration is feedstock logistics—the steps necessary to move feedstocks from fields or collection areas to ethanol production plants. For agricultural and forestry feedstocks, these steps include harvesting, transportation, storage, and preprocessing.
Today, U.S. ethanol is primarily produced from corn crops by dry-mill or wet-mill processing. Although wet-mill facilities were common in the industry's early days, dry-mill facilities now account for more than 80% of industry capacity. Between 2000 and 2007, the number of ethanol plants more than doubled and production capacity tripled in the United States.
Most of the growth came from dry-mill plants because they are dedicated and optimized for the production of ethanol. Dry-mill plants are typically smaller than wet-mill plants and use less energy per gallon of ethanol produced. In both dry- and wet-mill plants, the production of co-products consumes a third or more of total process energy. These co-products provide an important revenue source to ethanol producers.
Safety
Ethanol is less toxic than gasoline. Ethanol vapors disperse more rapidly than gasoline, lowering concentrations to safe levels more quickly after an accident.
Costs
E85 typically costs less than gasoline on a gallon-for-gallon basis, but more than gasoline on an energy-equivalent basis.
Availability
As of 2008, more than 1,400 U.S. fueling stations offered E85 to the more than 6 million FFVs on U.S. roadways. Stations are more common in the corn belt (Minnesota, Iowa, Illinois) but are spreading throughout the country. In fact, E85 is now offered in more than 40 states. See E85 Fueling Station Locations for sites near you.
Ethanol producers face unique distribution challenges. Most ethanol plants are concentrated in the Midwest United States, but gasoline consumption is highest along the East and West Coasts. The volume of ethanol currently used in transportation is relatively small compared with the gasoline market. The ethanol produced generally can be absorbed in local or regional markets as E10 or E85, providing benefits to those markets. However, as ethanol production increases nationwide, distribution will become a more critical issue.
Most ethanol plants distribute their fuel by truck and rail. Some larger plants are located near navigable waterways and can ship their ethanol by barge—a more economical option. See Percent of U.S. Ethanol-Related Materials Transported by Mode (xls), 2005. The Energy Information Administration report Review of Transportation Issues and Comparison of Infrastructure Costs for a Renewable Fuels Standard discusses rail and water transport.
E85 Fueled vehicles in DAS Fleet
- Chevrolet Impala
- Chevrolet Silverado CK1500
- Chevrolet Tahoe
- Dodge Caravan
- Dodge Grand Caravan
- Ford Explorer
- Ford Ranger
- Ford Ranger
- Ford Taurus
- Ford Police Interceptor
- Jeep Grand Cherokee
Source: US Department of Energy, Energy Efficiency and Renewable Energy, Alternate Fuels & Advanced Vehicles Data Center: http://www.afdc.energy.gov/afdc/
Updated: 02/20/2009
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