Corn ethanol
Corn ethanol is a biofuel derived from corn, primarily used as an alternative to fossil fuels and often blended with gasoline. The United States is the largest producer of corn ethanol, accounting for approximately 55% of global production as of 2021. The production process involves fermenting corn biomass, and it yields various commercial by-products, including livestock feed and cooking oil. The most common ethanol blend in the U.S. is E10, which contains 10% ethanol, though higher blends like E15 and E85 are available for specific vehicles.
As a renewable energy source, corn ethanol is praised for potentially reducing carbon emissions and promoting energy independence. However, its production also raises concerns regarding environmental impact, food supply competition, and agricultural practices. The increasing demand for corn for biofuel has been linked to food price increases, particularly in countries where corn is a staple. Government incentives, such as subsidies and mandated ethanol blends, have significantly supported the corn ethanol industry, fostering its growth despite ongoing debates about its sustainability and long-term viability as a fuel source.
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Corn ethanol
Summary: The United States is the leading producer of corn ethanol, a corn-derived alcohol fuel. While corn ethanol can be used as an alternative to fossil fuels, the steady increase in its popularity owes more to its use as a gasoline additive. The process of manufacturing the fuel yields numerous commercial by-products.
Corn ethanol is produced through the fermentation, chemical processing, and distillation of corn biomass, and is the most common type of ethanol fuel produced in the United States, which is the world’s leading producer of ethanol fuel (accounting for about 55 percent of global production in 2021). Ethanol is ethyl alcohol, the same alcohol found in alcoholic beverages, though because of legal and tax restrictions, ethanol sold for purposes other than consumption is adulterated with methanol (wood alcohol, which is highly toxic) or additives that make it too bitter to willingly ingest. Though fuel is its most common use, ethanol can also be used as a chemical feedstock for producing organic compounds, as an antiseptic (it is the key ingredient in most hand sanitizer, leading to the teenager practice of sanitizer consumption), and as a solvent.
Most ethanol fuel is used as motor fuel, in the form of fuel mixtures of gasoline with low levels of ethanol. The term gasohol is sometimes used for mixtures of less than 25 percent ethanol (the amount used in Brazil, the second-largest ethanol producer). A common ratio in the United States is 10 percent, commonly called E10; most retail motor fuel in the United States is E10. Blends with greater proportions of ethanol are not commonly used in the United States because only recent model cars are certified by the Environmental Protection Agency to use them without damage; a study on the safety of E15 remains incomplete, and as of a 2011 ruling, E15 could only be sold accompanied with a warning that it can only be used in flex-fuel vehicles and passenger vehicles with a model year of 2001 or later. E15 is expected to supplant E10 in the United States as older cars fall out of use. E10 is also used in Thailand and Finland, and has become more available in Australia. In the United States, E70 and E75 are reduced-ethanol versions of E85 sold during the winter months to avoid cold starting problems, a practice also followed in Sweden. E85 is the standard fuel for flex-fuel vehicles, which have internal combustion engines designed to run on more than one fuel; there are 10 million such cars, light trucks, and motorcycles in the United States, and there are another 17 million worldwide. (Popular models include the flex-fuel Chevrolet Impala and the flex-fuel Ford Escape.) Because it is created from an agricultural crop, corn ethanol is a renewable energy source. Because it is produced domestically, it is less subject to price volatility than fossil fuels.
To produce corn ethanol, the corn is first milled. Wet milling steeps the corn in diluted sulfuric acid for one to two days, which separates the grain into its fiber, gluten, starch, and oil. Wet milling creates a number of corn products. Corn oil is sold for cooking and other purposes. The fiber is sold as corn gluten feed for livestock. The steeping liquid can be used to deice streets. The remaining water and starch can be processed either into corn syrup, modified corn starch, or corn ethanol. The process for turning the water and starch produced by wet milling into corn ethanol is substantially similar to the dry milling process. Dry milling grinds corn kernels into flour, which is then mixed with water and enzymes that convert the starch to dextrose (sugar). Yeast is added to convert the sugar to ethanol, just as in the process of natural fermentation or the fermenting of corn for bourbon or other whiskey.
The addition of ammonia balances the pH levels of the mix in order to maintain the ideal environment for the yeast, to maximize fermentation. Left to its own devices, fermentation will stall when the environment becomes too acidic or too alcoholic for the yeast to thrive, even if there is remaining sugar to convert. By-products of wet milling include the carbon dioxide released by fermentation, which is used to manufacture dry ice or to carbonate soft drinks, and a nutrient-rich mash of solids that is processed into feed for livestock. Most American corn ethanol is made by the dry milling process, which can be performed fairly simply.
In recent years, more and more corn has been diverted to the production of ethanol in response to the increased demand for biofuels, a demand driven by consumer concerns with environmental impacts, government incentives, and the volatility of fossil fuel prices. Corn ethanol has many considerable environmental and economic impacts, including its carbon intensity and its impact on the food supply. The use of arable land to produce biofuel was one of the factors in the food commodity price shocks of the early 21st century. The increased demand for corn also drove up the price of the crop in Mexico, where it is the staple grain. In addition to considering other crops as feedstock for ethanol—one of those often mentioned is algae, because its cultivation would not replace arable land already in use—there have been suggestions that the remnants from crop processing could be used to produce ethanol, in order to produce it as a by-product of agricultural activity that already exists, rather than replacing that activity.
Corn ethanol production has been strongly supported by subsidies and other government incentives. The Energy Policy Act of 2005 mandated the use of ethanol blends, guaranteeing demand for corn ethanol; despite this guaranteed demand, corn crops (regardless of end use) receive the largest share of the United States’ generous agricultural subsidies, about a third of the total. Until 2012, ethanol producers received a $0.45 per gallon subsidy on top of that crop subsidy. A tariff on ethanol imports maintains domestic producers’ advantage. In 2020, less than 2 percent of American corn is grown for human food, and even that figure is inflated by the subsidy-driven reliance on corn syrup as a sweetener in the food industry. 35 percent was grown for animal feed and 31 percent was grown for biofuel. Although environmentalists who support the use of ethanol have touted it as just a transitional fuel to reduce reliance on fossil fuels before adopting an even greener energy, market factors suggest that the profitability of corn ethanol, and the safety net provided by subsidies to mitigate risk, will make it difficult to change.
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