SP700-B UTBiofuelsInitiative Ethanol: A Primer Samuel Jackson, Research Associate Office of Bioenergy Programs Introduction Ethanol has become a major within our nation’s borders. fermenting sugars or converted player in alternative fuels over the The feedstocks, conversion and starch into alcohol. The chemical last few years. Our nation uses distribution all take place within makeup of ethanol is the same, approximately 384 million gallons the country. With recent federal whether it is made from grains of gasoline each day. That amounts legislation, national goals are to or plant materials. It is primarily to more than 140 billion gallons replace 30 percent of our petroleum produced from corn grain, but each year. The United States consumption with biofuels, such as can also be made from the sugar imports approximately 60 percent ethanol. Tennessee currently has, in cellulosic biomass. Cellulosic of the oil it uses. A significant installed or under development, biomass is simply plant material portion of that oil is imported from about 480 million gallons per year from which sugar is extracted. countries that are not stable and of ethanol production capacity. It is Ethanol can be burned, much like are in volatile parts of the world. projected that between corn-based gasoline, to produce energy that Many citizens feel that from a ethanol and cellulosic ethanol, powers vehicles and machinery. national security standpoint, it Tennessee has the potential to is in the nation’s best interests to produce at least 1 billion gallons Producing Ethanol from Grain reduce our reliance on foreign of ethanol each year, replacing 30 Traditionally, alcohols, including sources of energy, such as oil, and percent of its gasoline consumption. ethanol, have been produced from move to renewable, domestically corn and other grains. Corn is the produced fuels. Ethanol is an ethyl alcohol that can primary choice, because a kernel be used as a liquid fuel. It is made of corn is approximately two-thirds Ethanol is one of these renewable up of oxygen, hydrogen and carbon starch, the component that ethanol fuels that can be produced (CH3CH2OH ). Ethanol is made by manufacturers depend upon. In early 2008, production levels of corn ethanol reached 8.1 billion gallons per year at 143 plants in the United States. The type of corn used for ethanol production is called field corn and is not the “sweet” corn used for human consumption.

A general expectation of corn ethanol is that one bushel of corn produces 2.8 gallons of fuel. Two primary methods are used to produce ethanol from corn: wet milling and dry milling. The wet milling process begins when the grain is soaked in a dilute water and acid mixture for one to two days. The soaking begins to break Switchgrass is one of the materials that can be used to produce ethanol from the corn down into the more simple cellulose. Credit: Marie Walsh, University of Tennessee compounds and chemicals of which it is made. The resulting mixture, UTBiofuelsInitiative 2 or slurry, is then passed through a most common organic compounds release of cellulose for ethanol variety of separation procedures to on earth. By using cellulose to conversion. A dilute acid solution separate out four main parts: corn oil, create ethanol, a wide variety of can also be used as a pretreatment. gluten, fiber and starch. The corn oil, new sources of sugar are available gluten and fiber are often dried and for ethanol production, and Next, the biomass goes through a sold as animal feeds. This product is producers do not have to rely on a process called enzymatic hydrolysis. very high in protein content and is in specific grain commodity. Materials This process uses plant enzymes to demand by animal producers. commonly used for cellulosic initiate specific chemical reactions. ethanol include corn stalks, wood The pretreatment process allows The starch is put into a fermentation residues and chips, wheat straw, enzymes to gain access to the process, a step that can take up to 50 fast-growing trees, native grasses cellulose in the plant cells. The hours. Yeast is added to the starchy and sugarcane. reactions caused by the enzymes “mash” − as it was called in the break the cellulose molecules moonshine days − and the mixture Cellulosic ethanol technologies, down to simple sugars. Once this is stirred. The yeast metabolizes the however, are not as well developed process is complete, the sugars are starch, in the absence of oxygen, as the grain technologies. The separated and fermented and produces ethanol and carbon primary difference between the into ethanol. dioxide in the process. The resulting two is that it is difficult to access liquid is called “beer,” and it is and free the cellulose in plant Regardless of how the ethanol is transferred to distillation columns cells. Another challenge lies in produced, a key step at the end of where the ethanol is separated from converting cellulose to simple the process is to blend the pure the residual mash. The ethanol sugars for fermenting. Two different ethanol with about 5 percent is then processed to remove any processes, biochemical conversion denaturant, most often regular residual water, and once that is and thermochemical conversion, gasoline. This blending makes complete, the result is pure ethanol. can be used to access cellulose and the ethanol undrinkable and not convert it into simple sugars. Once subject to the alcohol tax placed on In the dry milling process, the corn these processes are complete, the alcoholic beverages. grain is ground into flour called fermentation process is identical to “meal.” The component parts of the ethanol made from grain. Common Concerns about grain are not separated out here, Ethanol Production as in the wet milling method. The In the thermochemical process, Oftentimes, biofuels are evaluated meal is mixed with water and forms cellulosic biomass is gasified. for how much energy it takes to the mash. Enzymes, proteins that Gasification is where the biomass produce the fuel versus the amount accelerate chemical reactions, are is quickly superheated in a of energy provided by the fuel. added to the mixture and convert the low-oxygen environment. This This is called the fossil energy starch to dextrose, a simple sugar. produces a gas called “syngas” and ratio. For corn ethanol, the fossil The mash is then heated to a high a residue called “char.” Syngas is energy ratio is 1.8. For cellulosic temperature to kill any bacteria primarily made up of hydrogen ethanol, the ratio is at least 5 and, prior to fermentation. After heating, and carbon monoxide. The syngas in some studies, as high as 10. In the mash is fermented in a similar is then passed through a specially other words, for every unit of fossil method to wet milling. In dry milling, designed reactor, where catalysts energy it takes to make ethanol, the mash left after fermentation is turn the gas into ethanol. The char at least 1.8 units of equivalent dried and sold as dried distillers grains can be used as fertilizer or in other energy is produced. We get more with solubles (DDGS) as an animal products. energy out of ethanol than it takes feed. The carbon dioxide from the to produce it. Gasoline has a fossil process can be captured and often In the biochemical process, living energy ratio of 0.8, meaning it takes used for other purposes, such as organisms, enzymes, are used more energy to produce than is carbonating soft drinks. to convert cellulosic biomass to provided by the end fuel. ethanol. The biomass is brought Producing Ethanol from into the conversion facility and Another common concern related Cellulosic Materials typically ground or chopped into to ethanol production is odor Another source of sugars to small pieces. It is then subjected to produced in the manufacturing manufacture ethanol comes from a high-pressure steam treatment, process. The primary source of cellulose, which is found in the which starts breaking down the odor in a corn ethanol plant is walls of plant cells and is one of the plant cell walls and begins the the dried distiller’s grains with UTBiofuelsInitiative 3 solubles (DDGS). Prior to being prices increase, so do costs of sold as animal feed, DDGS are things depending upon petroleum. dried. This process produces Fertilizer, herbicides and pesticides aldehydes, ketones and lactic acid, that crop producers depend upon all of which combine to produce a are derived in some way from foul odor. New technologies allow petroleum. Input costs have gone producers to minimize the impacts up dramatically since 2007, with of these odors by using scrubbing some herbicide and pesticide costs technologies to neutralize the smell. doubling. Fuel costs for planting, Cellulosic ethanol facilities do not harvesting and transporting corn have this odor problem as they have also increased. Concern has have no DDGS. Another source also been raised about the amount of odor is from the fermentation of corn exported from the US to procedure, and the exhaust it other countries. Many nations produces. Both corn and cellulosic depend upon our corn for their ethanol plants must contend with food supplies. In reality, though, US this issue. Scrubber technology corn exports have increased, up 6 is used here as well. The exhaust percent between 2006 and 2007, to is passed through the scrubbers, their highest levels since 1990. where organic materials responsible E-85 dispensers are clearly labeled. You for the odor are removed prior to All of these factors, including can see the yellow gas cap indicating a release from the plant. demand, have affected corn prices. flex fuel vehicle in the background. Credit: Higher corn prices may impact food Sam Jackson, University of Tennessee Water usage in producing ethanol markets, as it will cost more to feed is also an issue. Producing ethanol animals and more to buy products some ratio of ethanol and gasoline. is a water-intensive process. derived from field corn. There is a In most cases, ethanol is sold as Making one gallon of gasoline from limit to the amount of ethanol that E-10 (90 percent gasoline and 10 petroleum takes about 1.5 gallons can be produced from corn without percent ethanol) or E-85 (85 percent of water. Ethanol from corn takes significantly impacting food and ethanol and 15 percent gasoline). about 4 gallons of water for every related markets. This is one reason In the US, no road vehicles can gallon produced. Current cellulosic why cellulosic ethanol, produced use 100 percent ethanol due to ethanol production technology from crops with less effect on food the design of current engines. All requires 5-9 gallons of water per commodities, is continuing to current vehicle engines are designed gallon of ethanol made. However, be developed. to accommodate blends of up to demand for fresh water can be 10 percent ethanol or E-10 in their significantly reduced by recycling it Using Ethanol fuel with no problems. Ethanol through wastewater treatment prior Ethanol is primarily used as is relatively caustic to standard to reuse in the production process. a motor vehicle fuel. Though rubber seals, gaskets and hoses in producing ethanol is similar in the engine. Although recent studies Producing ethanol from corn cost to producing gasoline, it is less suggest blends up to 20 percent may also have an impact on food expensive per gallon than gasoline or E-20 may be suitable for use in and feed prices and availability. when purchasing E-85 at the pump. standard vehicles, blends greater As the ethanol industry has The reason is that the federal than 10 percent are not approved developed, more corn has been government currently subsidizes by either vehicle manufacturers diverted from traditional markets the production of ethanol at 51 nor the US EPA, due to possible to ethanol production. More cents per gallon, primarily to long-term effects on fuel system recently, corn commodity prices promote the development of the components as well as unanswered have sky rocketed to more than ethanol industry and to reduce the emission questions. $5 per bushel. Many relate this nation’s reliance on foreign oil. New increase in corn prices to ethanol legislation has been proposed to Automakers now produce vehicles demand. While this demand may create a different, higher subsidy that are called “flex fuel” vehicles. have some impact on corn prices for cellulosic ethanol. These vehicles have seals, gaskets and availability, it is important and hoses that are lined with to look at the bigger picture to Ethanol is sold as a blend, meaning Teflon™ to prevent deterioration assess the situation. As petroleum what you purchase at the pump is when using high concentrations UTBiofuelsInitiative 4 of ethanol. Traditional vehicles do A common concern when using public E-85 stations in the nine not have this Teflon™ lining. Other ethanol is that vehicles using E-85 get Southeastern states. More than half common features that are unique to less fuel economy (miles per gallon) of those, 46, are in South Carolina flex-fuel vehicles are a stainless steel than when using regular gasoline. alone. Most states average 4-5 fuel tank and a sensor to measure A gallon of ethanol has about two- public stations. In Tennessee, most the ethanol/gasoline ratio to adjust thirds the energy content of that of fuel stations now have E-10 as their engine performance. If you have or a gallon of gasoline. To travel the standard fuel. The next time you fill purchase one of these vehicles, you same distance provided by a gallon up your car’s tank, look for a sticker can use a fuel mixture of up to 85 of gasoline, it would take 1.03 gallons on the pump indicating that the percent ethanol (E-85). If you think of E10 and 1.33 gallons of E85. In fuel is E-10. This will not hurt your you may have a flex-fuel vehicle, today’s engines, automobiles using vehicle and will most likely improve check for a sticker or other marking E85 typically see a mileage decrease engine performance. In fact, most inside your car’s fuel filler door and of 10-25 percent, depending upon motorboat and lawnmower engines review your vehicle’s owner’s manual the vehicle, compared to gasoline. are certified to run on E-10. to be certain before filling your tank. Though mileage may be an issue, There are about 6 million flex fuel ethanol does improve engine In early 2008, Tennessee had only vehicles on the road in the US. Only performance, as it has a much higher nine public gas stations selling vehicles specifically designed to use octane rating (113) than regular E-85. However, through the Green higher concentrations of ethanol gasoline (87). The Indy Racing Island Corridor grant program, should use E-85. Using an ethanol League©, known for the Indianapolis at least 22 more public pumps concentration of higher than 10 500, runs all of their cars on 100 are on the horizon. The program percent in non-flex fuel vehicles may percent ethanol for superior engine is directed by the Governor’s void the manufacturer’s warranty performance. Alternative Fuels Working Group and cause long-term problems, such and coordinated by the Tennessee as failing fuel pumps and failure Even with the loss in fuel Department of Transportation. To of hoses and gaskets. Check with economy, ethanol offers many locate the E-85 pump closest to you, your manufacturer for details. It is environmental benefits. Overall, visit http://www.eere.energy.gov/afdc/ possible to convert a vehicle to meet ethanol significantly reduces ethanol/ethanol_locations.html. flex-fuel standards, though it may be greenhouse gas (GHG) emissions cost-prohibitive. compared to gasoline, though For More Information some, such as acetalhyde, may To learn more about the production slightly increase. An E-85 blend of and utilization of ethanol, please corn-based ethanol reduces GHG visit one of these resources. emissions by 10-20 percent per BioWeb: An online resource for mile. An E-85 blend of cellulosic bioenergy and bioproducts – ethanol reduces GHG emissions by http://bioweb.sungrant.org at least 60 percent per mile. The largest percent reduction in specific Renewable Fuels Association – components of GHGs is in carbon http://www.ethanolrfa.org/ monoxide and sulfates. US Dept. of Energy Alternative Flex Fuel vehicles are typically labeled with this emblem. It can be found on Where can I purchase ethanol? Fuels and Advanced Vehicles Data tailgates or trunks of newer flex Ethanol is less readily available Center - http://www.eere.energy.gov/ fuel vehicles. Credit: Sam Jackson, in the Southeast as compared to afdc/fuels/ethanol.html University of Tennessee the Midwestern US. There are 80

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