Corn ethanol is

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

produced from corn biomass and is the main source of

ethanol fuel in the United States The United States became the world's largest producer of ethanol fuel in 2005. The U.S. produced 15.8 billion gallon, U.S. liquid gallons of ethanol fuel in 2019, and 13.9 billion gallon, U.S. liquid gallons (52.6 billion liters) in 2011, an i ...

, mandated to be blended with gasoline in the

Renewable Fuel Standard The Renewable Fuel Standard (RFS) is an American federal program that requires transportation fuel sold in the United States to contain a minimum volume of renewable fuels. It originated with the Energy Policy Act of 2005 and was expanded and exte ...

. Corn ethanol is produced by

ethanol fermentation Ethanol fermentation, also called alcoholic fermentation, is a biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as by-products. Because yeasts perform this ...

and

distillation Distillation, or classical distillation, is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation, usually inside an apparatus known as a still. Dry distillation is the heat ...

. It is debatable whether the production and use of corn ethanol results in lower

greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and ...

than gasoline. Approximately 45% of U.S. corn

croplands A farm (also called an agricultural holding) is an area of land that is devoted primarily to agricultural processes with the primary objective of producing food and other crops; it is the basic facility in food production. The name is used f ...

are used for

production.

Uses

Since 2001, corn ethanol production has increased by more than several times. Out of 9.50 billions of bushels of corn produced in 2001, 0.71 billions of bushels were used to produce corn ethanol. Compared to 2018, out of 14.62 billions of bushels of corn produced, 5.60 billion bushels were used to produce corn ethanol, reported by the

United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...

. Overall, 95% of ethanol is produced from corn. Currently, corn ethanol is mainly used in blends with

gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organi ...

to create mixtures such as E10, E15, and

E85 E85 is an abbreviation typically referring to an ethanol fuel blend of 85% ethanol fuel and 15% gasoline or other hydrocarbon by volume. In the United States, the exact ratio of fuel ethanol to hydrocarbon may vary according to ASTM 5798 that ...

Ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...

is mixed into more than 98% of United States gasoline to reduce air pollution. Corn ethanol is used as an

oxygenate Oxygenated chemical compounds contain oxygen as a part of their chemical structure. The term usually refers to oxygenated chemical compounds added to fuels. Oxygenates are usually employed as gasoline additives to reduce carbon monoxide and soot ...

when mixed with

. E10 and E15 can be used in all engines without modification. However, blends like E85, with a much greater

content, require significant modifications to be made before an engine can run on the mixture without damaging the engine. Some vehicles that currently use

fuel, also called flex fuel, include, the

Ford Focus The Ford Focus is a compact car (C-segment in Europe) manufactured by Ford Motor Company since 1998. It was created under Alexander Trotman's Ford 2000 plan, which aimed to globalize model development and sell one compact vehicle worldwide. The ...

Dodge Durango The Dodge Durango is a mid-size sport utility vehicle (SUV) produced by Dodge in three generations starting with the 1998 model year. The first two generations were very similar in that both were based on the Dodge Dakota and Ram Pickup, both ...

, and Toyota Tundra, among others. The future use of corn ethanol as a main

replacement is unknown. Corn ethanol has yet to be proven to be as cost effective as

due to corn ethanol being much more expensive to create compared to

. Corn ethanol has to go through an extensive milling process before it can be used as a fuel source. One major drawback with corn ethanol, is the energy returned on energy invested (

EROI EROI or the Eastman Rochester Organ Initiative is a project run by the Eastman School of Music with the goal of creating a unique collection of organ instruments in Rochester, New York. The Italian Baroque organ The first milestone of the proje ...

), meaning the energy outputted in comparison to the energy required to output that energy. Compared to oil, with an 11:1

, corn ethanol has a much lower

of 1.5:1, which, in turn, also provides less mileage per gallon compared to gasoline. In the future, as technology advances and oil becomes less abundant, the process of milling may require less energy, resulting in an

closer to that of oil. Another serious problem with corn ethanol as a replacement for

, is the engine damage on standard vehicles. E10 contains ten percent

and is acceptable for most vehicles on the road today, while E15 contains fifteen percent

and is usually prohibited for cars built before 2001. However, with the hope to replace

in the future,

, which contains 85%

, requires engine modification before an engine can last while processing a high volume of

for an extended period of time. Therefore, most older and modern day vehicles would become obsolete without proper engine modifications to handle the increase in corrosiveness from the high volume of

. Also, most gas stations do not offer refueling of E85 vehicles. The

reports that only 3,355 gas stations, out of 168,000, across the United States, offer

refueling for

vehicles.

Production process

There are two main types of corn ethanol production: dry milling and

wet milling Wet-milling is a process in which feed material is steeped in water, with or without sulfur dioxide, to soften the seed kernel in order to help separate the kernel’s various components. For example, wet-milling plants can separate a 56-pound bu ...

, which differ in the initial grain treatment method and co-products.

Dry milling

The vast majority (≈80%) of corn ethanol in the United States is produced by dry milling. In the dry milling process, the entire

corn kernel Corn kernels are the fruits of corn (called maize in many countries). Maize is a grain, and the kernels are used in cooking as a vegetable or a source of starch. The kernel comprise endosperm, germ, pericarp, and tip cap. One ear of corn contai ...

is ground into flour, or "mash," which is then slurried by adding water. Enzymes are added to the mash to hydrolyze the starch into

simple sugar Monosaccharides (from Greek ''monos'': single, '' sacchar'': sugar), also called simple sugars, are the simplest forms of sugar and the most basic units (monomers) from which all carbohydrates are built. They are usually colorless, water-solub ...

Ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

is added to control the pH and as a nutrient for the

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...

, which is added later. The mixture is processed at high-temperatures to reduce the bacteria levels. The mash is transferred and cooled in

fermenter Industrial fermentation is the intentional use of fermentation in manufacturing products useful to humans. In addition to the mass production of fermented foods and drinks, industrial fermentation has widespread applications in chemical industry. ...

Yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...

are added, which ferment the sugars into

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

. The entire process takes 40 to 50 hours, during which time the mash is kept cool and agitated to promote

activity. The

is purified through a combination of distillation and dehydration to create fuel ethanol. The mash is then transferred to

distillation column A fractionating column or fractional column is an essential item used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on the differences in volatilities. Fractionating columns are used in ...

s, where the

is removed from the

silage Silage () is a type of fodder made from green foliage crops which have been preserved by fermentation to the point of acidification. It can be fed to cattle, sheep and other such ruminants (cud-chewing animals). The fermentation and storage ...

. The

is dehydrated to about 200 proof using a

molecular sieve A molecular sieve is a material with pores (very small holes) of uniform size. These pore diameters are similar in size to small molecules, and thus large molecules cannot enter or be adsorbed, while smaller molecules can. As a mixture of molecu ...

system. A denaturant such as

is added to render the product undrinkable. The product is then ready to ship to gasoline retailers or terminals. The remaining

is processed into a highly nutritious

livestock feed Fodder (), also called provender (), is any agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food given to the animals (includin ...

known as distiller's dried grains and solubles (DDGS). The

released from the process is used to carbonate beverages and to manufacture

dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...

Wet milling

, the corn grain is separated into components by steeping in dilute sulfuric acid for 24 to 48 hours. The slurry mix then goes through a series of grinders to separate out the corn

germ Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embryo ...

. The remaining components of fiber,

gluten Gluten is a structural protein naturally found in certain cereal grains. Although "gluten" often only refers to wheat proteins, in medical literature it refers to the combination of prolamin and glutelin proteins naturally occurring in all grai ...

, and starch are segregated using screen, hydroclonic, and centrifugal separators. The corn starch and remaining water can be fermented into

through a similar process as dry milling, dried and sold as modified corn starch, or made into corn syrup. The

protein and steeping liquor are dried to make a

corn gluten meal Corn gluten meal is the principal protein of corn (maize) endosperm consisting mainly of zein and glutelin. It is a byproduct of corn processing that has historically been used as an animal feed. Despite the name, corn gluten does not contain tr ...

that is sold to the livestock industry. The heavy steep water is also sold as a feed ingredient and used as an alternative to salt in the winter months. Corn oil is also extracted and sold.

Environmental issues

Corn ethanol results in lower

than

and is fully biodegradable, unlike some

fuel additives A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

such as

MTBE Methyl ''tertiary''-butyl ether (MTBE), also known as methyl tert-butyl ether and ''tert''-butyl methyl ether, is an organic compound with a structural formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly sol ...

.Ethanol Myths and Facts
However, because energy to run many U.S. distilleries comes mainly from

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

plants, there has been considerable debate on the sustainability of corn ethanol in replacing fossil fuels. Additional controversy relates to the large amount of arable land required for crops and its impact on grain supply and direct and indirect land use change effects. Other issues relate to

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

, water use for

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...

and processing,

energy balance Energy balance may refer to: * Earth's energy balance, the relationship between incoming solar radiation, outgoing radiation of all types, and global temperature change. * Energy accounting, a system used within industry, where measuring and anal ...

, and emission intensity for the full life cycle of ethanol production. Originally published online in Science Express on 7 February 2008. See Letters to ''Science'' by Wang and Haq. There are critics to these findings for assuming a worst-case scenario.Oxfam Briefing Paper 114, figure 2 pp.8 Originally published online in Science Express on 7 February 2008. There are rebuttals to these findings for assuming a worst-case scenario.

Greenhouse gas emissions

Several full life cycle studies have found that corn ethanol reduces

well-to-wheel Life cycle assessment or LCA (also known as life cycle analysis) is a methodology for assessing environmental impacts associated with all the stages of the life cycle of a commercial product, process, or service. For instance, in the case of ...

by up to 50 percent compared to gasoline. However, other research has concluded that corn ethanol produces more carbon emissions per unit of energy than gasoline, when factoring in fertilizer use and land use change Ethanol-blended fuels currently in the market – whether E10 or E85 – meet stringent tailpipe emission standards.

Croplands

One of the main controversies involving corn ethanol production is the necessity for arable cropland to grow the corn for ethanol, which is then not available to grow corn for human or animal consumption. In the United States, 40% of the acreage designated for corn grain is used for corn ethanol production, of which 25% was converted to ethanol after accounting for co-products, leaving only 60% of the crop yield for human or animal consumption.

Economic impact of corn ethanol

The

Renewable Fuels Association The Renewable Fuels Association (RFA) represents the ethanol industry promoting policies, regulations, and research and development initiatives that will lead to the increased production and use of ethanol fuel. First organized in 1981, RFA serves ...

(RFA), the ethanol industry's lobbying group, claims that ethanol production increases the price of corn by increasing demand. The RFA claims that ethanol production has positive economic effect for US farmers, but it does not elaborate on the effect for other populations where field corn is part of the staple diet. An RFA lobby document states that "In a January 2007 statement, the USDA Chief Economist stated that farm program payments were expected to be reduced by some $6 billion due to the higher value of a bushel of corn. Corn production in 2009 reached over 13.2 billion bushels, and a per acre yield jumped to over 165 bushels per acre. In the United States, 5.05 billion bushels of corn were used for

production out of 14.99 billion bushels produced in 2020, according to

USDA The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of com ...

data. According to the U.S. Department of Energy's Alternative Fuels Data Center, "The increased ethanol roductionseems to have come from the increase in overall corn production and a small decrease in corn used for animal feed and other residual uses. The amount of corn used for other uses, including human consumption, has stayed fairly consistent from year to year." This does not prove there was not an impact on food supplies: Since U.S. corn production doubled (approximately) between 1987 and 2018, it is probable that some cropland previously used to grow other food crops is now used to grow corn. It is also possible or probable that some marginal land has been converted or returned to agricultural use. That may have negative environmental impacts.

Alternative biomass for ethanol

Remnants from food production such as corn stover could be used to produce ethanol instead of food corn. Ethanol derived from sugar-beet as used in Europe or sugar-cane in Brazil has up to 80% reduction in

. The use of cellulosic biomass to produce

is considered second generation biofuel that are considered by some to be a solution to the food versus fuel debate, and has the potential to cut life cycle

by up to 86 percent relative to gasoline.

References

External links

Better Than Corn? Algae Set to Beat Out Other Biofuel Feedstocks
(

Worldwatch Institute The Worldwatch Institute was a globally focused environmental research organization based in Washington, D.C., founded by Lester R. Brown. Worldwatch was named as one of the top ten sustainable development research organizations by Globescan Su ...

). *The End of Cheap Food. (Cover Story). 2007 Economist 385(8558):11-12. *Energy Policy Act of 2005. 2005 Public Law 109-58. *Pimentel, David. 2009 Corn Ethanol as Energy. Harvard International Review 31(2):50-52. *Scully, Vaughan. 2007 Effects of the Biofuel Boom. BusinessWeek Online:26-26. *Waltz, Emily. 2008 Cellulosic Ethanol Booms Despite Unproven Business Models. Nature Biotechnology 26(1):8-9.
Cornstarch Substitute

Martin,Jeremy. 2017. Fueling a Clean Transportation Future.

Union of Concerned Scientists The Union of Concerned Scientists (UCS) is a nonprofit science advocacy organization based in the United States. The UCS membership includes many private citizens in addition to professional scientists. Anne Kapuscinski, Professor of Environmenta ...

. {{DEFAULTSORT:Corn Ethanol Ethanol fuel Ethanol