Ethanol
Ethanol is a renewable, domestically produced alcohol fuel made from plant material, such as corn, sugar cane, or grasses. Using ethanol can reduce oil dependence and greenhouse gas (GHG) emissions. Ethanol fuel use in the U.S. has increased dramatically from about 1.7 billion gallons in 2001 to about 12.6 billion in 2020.
E10 and E15
Label required on pumps that dispense E15. Label reads as follows: ATTENTION. E15, up to 15% ethanol. Use only in (1) 2001 and newer passenger vehicles (2) flex-fuel vehicles. Don't use in other vehicles, boats or gasoline-powered equipment. It may cause damage and is prohibited by Federal law. E10 and E15 are blends of ethanol and gasoline. The number after the "E" indicates the percentage of ethanol by volume.
Most of the gasoline sold in the U.S. contains up to 10% ethanol—the amount varies by region. All automakers approve blends up to E10 in their gasoline vehicles.
As of 2011, EPA began allowing the use of E15 in model year 2001 and newer gasoline vehicles. Pumps dispensing E15 must be labeled (see example). A vehicle's owner manual may indicate the maximum ethanol content recommended for it by the automaker.
Ethanol contains about one-third less energy than gasoline. So, vehicles will typically go 3% to 4% fewer miles per gallon on E10 and 4% to 5% fewer on E15 than on 100% gasoline.
[Footnotes omitted.] [Emphasis added.]
Recent Study Finds Ethanol More Cartbon Intensive Than Plain Gasoline
From Reuters, "U.S. corn-based ethanol worse for the climate than gasoline, study finds" By Leah Douglas, February 14, 2022, 5:12 PM EST, Last Updated 2 months ago:
Feb 14 (Reuters) - Corn-based ethanol, which for years has been mixed in huge quantities into gasoline sold at U.S. pumps, is likely a much bigger contributor to global warming than straight gasoline, according to a study published Monday.
The study [Environmental outcomes of the US Renewable Fuel Standard], published in the Proceedings of the National Academy of Sciences, contradicts previous research commissioned by the U.S. Department of Agriculture (USDA) showing ethanol and other biofuels to be relatively green.*** “Corn ethanol is not a climate-friendly fuel,” said Dr. Tyler Lark, assistant scientist at University of Wisconsin-Madison Center for Sustainability and the Global Environment and lead author of the study.
The research, which was funded in part by the National Wildlife Federation and U.S. Department of Energy, found that ethanol is likely at least 24% more carbon-intensive than gasoline due to emissions resulting from land use changes to grow corn, along with processing and combustion.
[Emphasis added.]
Geoff Cooper, president and CEO of the Renewable Fuels Association, the ethanol trade lobby, called the study "completely fictional and erroneous," arguing the authors used "worst-case assumptions [and] cherry-picked data."
Under the U.S. Renewable Fuel Standard (RFS), a law enacted in 2005, the nation's oil refiners are required to mix some 15 billion gallons of corn-based ethanol into the nation's gasoline annually. The policy was intended to reduce emissions, support farmers, and cut U.S. dependence on energy imports.
As a result of the mandate, corn cultivation grew 8.7% and expanded into 6.9 million additional acres of land between 2008 and 2016, the study found. That led to widespread changes in land use, including the tilling of cropland that would otherwise have been retired or enrolled in conservation programs and the planting of existing cropland with more corn, the study found.
Tilling fields releases carbon stored in soil, while other farming activities, like applying nitrogen fertilizers, also produce emissions.
A 2019 study from the USDA, which has been broadly cited by the biofuel industry, found that ethanol’s carbon intensity was 39% lower than gasoline, in part because of carbon sequestration associated with planting new cropland.
But that research underestimated the emissions impact of land conversion, Lark said.
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