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Politicians, auto companies, and the media have been trumpeting ethanol as a solution to America’s oil dependence and the environmental and economic problems that go along with it. Should you believe the hype?
Most of the ethyl alcohol, or ethanol, used in vehicle fuel is produced by fermentation of a sugar solution. In the United States, most ethanol is currently derived from the starches in corn kernels; other types of plant material such as grasses, wood, and agricultural wastes can be used to make “cellulosic” ethanol (named for the long chains of sugars that are the main component of plant cell walls), but this process is more complex. Researchers are working to make cellulosic ethanol production more efficient and affordable.
Ethanol Blends
Ethanol offers many of the same benefits as gasoline and diesel, including ease of handling and storage, but it is typically blended with gasoline because ethanol does not evaporate well at cold temperatures—making it hard to start a car running on pure ethanol in cold weather. All of today’s gasoline-burning cars and trucks can use a blend of 10 percent ethanol (known as E10) or less without any engine modifications; E10 accounts for more than 99 percent of all fuel ethanol consumed in the United States.
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The Flex-Fuel Loophole
How automakers feed our oil addiction while appearing to endorse ethanol.
Almost 20 years ago, in an effort to stimulate alternative-fuel use and reduce oil dependence, Congress created an incentive program that gives manufacturers of flex-fuel vehicles (FFVs) credit for higher fuel economy, under the assumption that vehicles running on ethanol blends reduce total gasoline consumption. The incentive assumes FFVs use E85 half the time; however, today’s FFVs use E85 only about one percent of the time. As a result, automakers are getting much more credit than they deserve.
Since 1998, the “Big Three” U.S. automakers—DaimlerChrysler, Ford, and General Motors—have taken advantage of this undeserved credit by increasing their production of FFVs, which show up on the books with reasonable fuel economy but are actually gas guzzlers. This loophole increased America’s oil dependence by 80,000 barrels per day in 2005 while earning the automakers sufficient credits to avoid $1.6 billion in Corporate Average Fuel Economy (CAFE) noncompliance fines.
The FFV credit was supposed to stimulate Americans’ use of ethanol, but it has proven a failure in this regard. Nevertheless, Congress has extended the credit through at least 2010 (and possibly 2014). UCS is continuing to advocate for more rational policies that can increase alternative-fuel use and fuel economy at the same time. | Blends of 85 percent ethanol, known as E85, can be used in “flex-fuel” vehicles (FFVs) designed to run on gasoline or any current ethanol blend. Nearly six million FFVs are on the road in the United States, including such popular models as the Ford F-150 pickup, Dodge Durango SUV, and Chevrolet Impala. Unfortunately, these vehicles operate on E85 less than one percent of the time, partly because less than 0.5 percent of all gas stations in the country carry E85 (most are in the Midwest; see map below) and partly because automakers only recently began advertising the fact that FFVs could run on E85. It is important to note that the U.S. Department of Energy allows the E85 label to be applied to blends containing between 74 and 85 percent ethanol.
From an air quality perspective, E85 is preferable to E10. E85 produces higher emissions of toxic formaldehyde and acetaldehyde but lower overall emissions of volatile organic compounds (VOCs, a key precursor to smog) than either E10 or pure gasoline. E10 actually produces higher VOC emissions than pure gasoline.
A Climate-friendly Fuel?
Because a gallon of ethanol releases less energy when burned than a gallon of gasoline or diesel, ethanol blends yield lower fuel economy than gasoline alone. But depending on how it is produced, ethanol can have superior global warming pollution performance compared with an energy-equivalent quantity of petroleum fuel. Most analyses indicate that corn ethanol, for example, delivers a modest reduction (10 to 20 percent) in global warming emissions over its full lifecycle—from corn seed to tailpipe—compared with gasoline (see the table). Cellulosic ethanol could reduce these emissions as much as 80 to 90 percent.
Reduction in Global Warming
Emissions Compared with Gasoline
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Pure Ethanol |
E85 |
E10 |
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10-20% |
8-16% |
~1% |
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80-90% |
63-71% |
5-6% | What accounts for this difference? Corn production requires a significant amount of fossil fuel, both for fertilizer production (which generally uses natural gas) and fuel for farm operations. Corn farming also generates substantial emissions of nitrous oxide (a heat-trapping gas 300 times as potent as carbon dioxide). In addition, many facilities where corn ethanol is produced use natural gas for fuel; if new production facilities use coal instead, the emission benefits of corn ethanol could be eliminated entirely. Cellulosic materials, on the other hand, require less fertilizer to grow, require less land to produce an equivalent amount of fuel, and the non-fermentable parts of the plant can be used as fuel rather than fossil fuels such as natural gas or coal.
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Number of Ethanol Fueling Stations by State |
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Driving the Future
The long-term potential for cellulosic ethanol production is significant, but key breakthroughs are needed to improve both crop yields and production efficiency. Aggressive scenarios indicate that this fuel could displace nearly 10 billion gallons of gasoline in 2025 and more than 100 billion gallons in 2050. However, this would represent only one-third of our gasoline demand at mid-century if we do not also take steps to improve fuel economy and reduce travel demand. As cellulosic ethanol production increases, it will also be important to ensure that the feedstocks are grown and harvested in a sustainable manner that protects wildlife habitats along with air, water, and soil quality.
Until these advances are made with cellulosic ethanol, we will have to rely on sustainably produced corn as a transitional step to expanded ethanol supplies and infrastructure. Corn’s long-term potential, though, is limited. We currently use roughly 15 percent of the U.S. corn crop to make ethanol, yet this displaces only about 2.3 percent of the gasoline used by our cars and light trucks each year. By 2025, even if we used all our corn to make ethanol (with nothing left for food or animal feed), we could only displace perhaps 15 percent of our gasoline demand.
While ethanol will not decrease the number of visits to the fuel pump, there is no question that it has a positive role to play in helping to reduce our petroleum dependence and the risks of dangerous global warming. But in the near term, we can achieve the greatest oil and consumer savings by improving the fuel economy of new vehicles. These efficiency gains will help lower the costs of an ethanol future.
Don MacKenzie is an engineer in the Clean Vehicles Program.
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