Ethanol is an alcohol that is used in gasoline—resulting ...
Ethanol is an alcohol that is used in gasoline—resulting in a cleaner-burning fuel with higher octane. Ethanol is currently blended into more than 50 percent of the nation’s fuel supply.
Ethanol has been blended in gasoline for decades—and billions of miles have been driven on ethanol-blended fuels.
Corn is the primary feedstock for ethanol production. About 20 percent of the nation’s corn supply went into ethanol in 2007—some 3.0 billion bushels. Ethanol can also be made from other grains such as sorghum as well as from “biomass” sources such as corn cobs, cornstalks, wheat straw, rice straw, switchgrass, vegetable and forestry waste and other organic matter.
Ethanol offers a number of benefits to our cars, our environment, our economy and our national security:
• Ethanol adds oxygen to gasoline—helping it combust more completely and reducing the level of toxic exhaust emissions
• Ethanol reduces our nation’s dangerous and expensive dependence on imported oil
• The ethanol industry creates jobs and investment across the nation—especially in rural areas
• Ethanol increases America’s fuel supply—helping keep gas prices down
• Ethanol adds value to America’s corn harvest and helps reduce the cost of federal farm programs
ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a powerful psychoactive drug and one of the oldest recreational drugs. It is best known as the type of alcohol found in alcoholic beverages and thermometers. In common usage, it is often referred to simply as alcohol or spirits.
Ethanol is a straight-chain alcohol, and its molecular formula is C2H5OH. Its empirical formula is C2H6O. An alternative notation is CH3–CH2–OH, which indicates that the carbon of a methyl group (CH3–) is attached to the carbon of a methylene group (–CH2–), which is attached to the oxygen of a hydroxyl group (–OH). It is a constitutional isomer of dimethyl ether. Ethanol is often abbreviated as EtOH, using the common organic chemistry notation of representing the ethyl group (C2H5) with Et.
The fermentation of sugar into ethanol is one of the earliest organic reactions employed by humanity. The intoxicating effects of ethanol consumption have been known since ancient times. In modern times, ethanol intended for industrial use is also produced from by-products of petroleum refining.[2]
Ethanol has widespread use as a solvent of substances intended for human contact or consumption, including scents, flavorings, colorings, and medicines. In chemistry, it is both an essential solvent and a feedstock for the synthesis of other products. It has a long history as a fuel for heat and light, and more recently as a fuel for internal combustion engines. Ethanol has been used by humans since prehistory as the intoxicating ingredient of alcoholic beverages. Dried residue on 9,000-year-old pottery found in China imply that Neolithic people consumed alcoholic beverages.[3]
Although distillation was well known by the early Greeks and Arabs, the first recorded production of alcohol from distilled wine was by the School of Salerno alchemists in the 12th century.[4] The first to mention absolute alcohol, in contrast with alcohol-water mixtures, was Raymond Lull.[4]
In 1796, Johann Tobias Lowitz obtained pure ethanol by filtering distilled ethanol through activated charcoal. Antoine Lavoisier described ethanol as a compound of carbon, hydrogen, and oxygen, and in 1808 Nicolas-Théodore de Saussure determined ethanol’s chemical formula.[5] Fifty years later, Archibald Scott Couper published ethanol's structural formula. It is one of the first structural formulas determined.[6]
Ethanol was first prepared synthetically in 1826 through the independent efforts of Henry Hennel in Great Britain and S.G. Sérullas in France. In 1828, Michael Faraday prepared ethanol by acid-catalyzed hydration of ethylene, a process similar to current industrial ethanol synthesis.[7]
Ethanol was used as lamp fuel in the United States as early as 1840, but a tax levied on industrial alcohol during the Civil War made this use uneconomical. The tax was repealed in 1906.[8] From 1908 onward, Ford Model T automobiles could be adapted to run on ethanol.[9] With the advent of Prohibition in 1920, ethanol fuel sellers were accused of being allied with moonshiners,[8] and ethanol fuel fell into disuse until late in Ethanol is a volatile, colorless liquid that has a strong characteristic odor. It burns with a smokeless blue flame that is not always visible in normal light.
The physical properties of ethanol stem primarily from the presence of its hydroxyl group and the shortness of its carbon chain. Ethanol’s hydroxyl group is able to participate in hydrogen bonding, rendering it more viscous and less volatile than less polar organic compounds of similar molecular weight.
Ethanol is a versatile solvent, miscible with water and with many organic solvents, including acetic acid, acetone, benzene, carbon tetrachloride, chloroform, diethyl ether, ethylene glycol, glycerol, nitromethane, pyridine, and toluene.[10][11] It is also miscible with light aliphatic hydrocarbons, such as pentane and hexane, and with aliphatic chlorides such as trichloroethane and tetrachloroethylene.[11]
Ethanol’s miscibility with water contrasts with that of longer-chain alcohols (five or more carbon atoms), whose water miscibility decreases sharply as the number of carbons increases.[12] The miscibility of ethanol with alkanes is limited to alkanes up to undecane, mixtures with dodecane and higher alkanes show a miscibility gap below a certain temperature (about 13 °C for dodecane[13]). The miscibility gap tends to get wider with higher alkanes and the temperature for complete miscibility increases.
Ethanol-water mixtures have less volume than the sum of their individual components at the given fractions. Mixing equal volumes of ethanol and water results in only 1.92 volumes of mixture.[10][14] Mixing ethanol and water is exothermic. At 298 K, up to 777 J/mol[15] are set free.
Mixtures of ethanol and water form an azeotrope at about 89 mole-% ethanol and 11 mole-% water[16] or a mixture of about 96 volume percent ethanol and 4% water at normal pressure and T = 351 K. This azeotropic composition is strongly temperature- and pressure-dependent and vanishes at temperatures below 303 K/[17]
the 20th centuryEthanol is a volatile, colorless liquid that has a strong characteristic odor. It burns with a smokeless blue flame that is not always visible in normal light.
The physical properties of ethanol stem primarily from the presence of its hydroxyl group and the shortness of its carbon chain. Ethanol’s hydroxyl group is able to participate in hydrogen bonding, rendering it more viscous and less volatile than less polar organic compounds of similar molecular weight.
Ethanol is a versatile solvent, miscible with water and with many organic solvents, including acetic acid, acetone, benzene, carbon tetrachloride, chloroform, diethyl ether, ethylene glycol, glycerol, nitromethane, pyridine, and toluene.[10][11] It is also miscible with light aliphatic hydrocarbons, such as pentane and hexane, and with aliphatic chlorides such as trichloroethane and tetrachloroethylene.[11]
Ethanol’s miscibility with water contrasts with that of longer-chain alcohols (five or more carbon atoms), whose water miscibility decreases sharply as the number of carbons increases.[12] The miscibility of ethanol with alkanes is limited to alkanes up to undecane, mixtures with dodecane and higher alkanes show a miscibility gap below a certain temperature (about 13 °C for dodecane[13]). The miscibility gap tends to get wider with higher alkanes and the temperature for complete miscibility increases.
Ethanol-water mixtures have less volume than the sum of their individual components at the given fractions. Mixing equal volumes of ethanol and water results in only 1.92 volumes of mixture.[10][14] Mixing ethanol and water is exothermic. At 298 K, up to 777 J/mol[15] are set free.
Mixtures of ethanol and water form an azeotrope at about 89 mole-% ethanol and 11 mole-% water[16] or a mixture of about 96 volume percent ethanol and 4% water at normal pressure and T = 351 K. This azeotropic composition is strongly temperature- and pressure-dependent and vanishes at temperatures below 303 K/[17]
. Hydrogen bonding causes pure ethanol to be hygroscopic to the extent that it readily absorbs water from the air. The polar nature of the hydroxyl group causes ethanol to dissolve many ionic compounds, notably sodium and potassium hydroxides, magnesium chloride, calcium chloride, ammonium chloride, ammonium bromide, and sodium bromide.[11] Sodium and potassium chlorides are slightly soluble in ethanol.[11] Because the ethanol molecule also has a nonpolar end, it will also dissolve nonpolar substances, including most essential oils[18] and numerous flavoring, coloring, and medicinal agents.
The addition of even a few percent of ethanol to water sharply reduces the surface tension of water. This property partially explains the “tears of wine” phenomenon. When wine is swirled in a glass, ethanol evaporates quickly from the thin film of wine on the wall of the glass. As the wine’s ethanol content decreases, its surface tension increases and the thin film “beads up” and runs down the glass in channels rather than as a smooth sheet.
Mixtures of ethanol and water that contain more than about 50% ethanol are flammable and easily ignited. Alcoholic proof is a widely used measure of how much ethanol (i.e., alcohol) such a mixture contains. In the 18th century, proof was determined by adding a liquor (such as rum) to gunpowder. If the gunpowder still burned, that was considered to be “100 degrees proof” that it was “good” liquor — hence it was called “100 degrees proof”.
Ethanol-water solutions that contain less than 50% ethanol may also be flammable if the solution is first heated. Some cooking methods call for wine to be added to a hot pan, causing it to flash boil into a vapor, which is then ignited to burn off excess alcohol.
Ethanol is slightly more refractive than water, having a refractive index of 1.36242 (at λ=589.3 nm and 18.35 °C).[10]
Ethanol is produced both as a petrochemical, through the hydration of ethylene, and biologically, by fermenting sugars with yeast.[19] Which process is more economical depends on prevailing prices of petroleum and grain feed stocks.
[edit] Ethylene hydration
Ethanol for use as an industrial feedstock or solvent (sometimes referred to as synthetic ethanol) is often made from petrochemical feed stocks, primarily by the acid-catalyzed hydration of ethylene, represented by the chemical equation
C2H4(g) + H2O(g) → CH3CH2OH(l).
The catalyst is most commonly phosphoric acid,[20] adsorbed onto a porous support such as silica gel or earth. This catalyst was first used for large-scale ethanol production by the Shell Oil Company in 1947.[21] The reaction is carried out with an excess of high pressure steam at 300 °C. In the U.S., this process was used on an industrial scale by Union Carbide Corporation and others; but now only LyondellBasell uses it commercially.
In an older process, first practiced on the industrial scale in 1930 by Union Carbide,[22] but now almost entirely obsolete, ethylene was hydrated indirectly by reacting it with concentrated sulfuric acid to produce ethyl sulfate, which was hydrolysed to yield ethanol and regenerate the sulfuric acid:[23]
C2H4 + H2SO4 → CH3CH2SO4H
CH3CH2SO4H + H2O → CH3CH2OH + H2SO4
[edit] Fermentation
Main article: Ethanol fermentation
Ethanol for use in alcoholic beverages, and the vast majority of ethanol for use as fuel, is produced by fermentation. When certain species of yeast (e.g., Saccharomyces cerevisiae) metabolize sugar they produce ethanol and carbon dioxide. The chemical equation below summarizes the conversion:
C6H12O6 → 2 CH3CH2OH + 2 CO2.
The process of culturing yeast under conditions to produce alcohol is called fermentation. This process is carried out at around 35–40 °C. Ethanol's toxicity to yeast limits the ethanol concentration obtainable by brewing. The most ethanol-tolerant strains of yeast can survive up to approximately 15% ethanol by volume.[24]
To produce ethanol from starchy materials such as cereal grains, the starch must first be converted into sugars. In brewing beer, this has traditionally been accomplished by allowing the grain to germinate, or malt, which produces the enzyme amylase. When the malted grain is mashed, the amylase converts the remaining starches into sugars. For fuel ethanol, the hydrolysis of starch into glucose can be accomplished more rapidly by treatment with dilute sulfuric acid, fungally produced amylase, or some combination of the two.[25]
[edit] Cellulosic ethanol
Main article: Cellulosic ethanol
Sugars for ethanol fermentation can be obtained from cellulose.[26][27] Until recently, however, the cost of the cellulase enzymes capable of hydrolyzing cellulose has been prohibitive. The Canadian firm Iogen brought the first cellulose-based ethanol plant on-stream in 2004.[28] Its primary consumer so far has been the Canadian government, which, along with the United States Department of Energy, has invested heavily in the commercialization of cellulosic ethanol. Deployment of this technology could turn a number of cellulose-containing agricultural by-products, such as corncobs, straw, and sawdust, into renewable energy resources. Other enzyme companies are developing genetically engineered fungi that produce large volumes of cellulase, xylanase, and hemicellulase enzymes. These would convert agricultural residues such as corn stover, wheat straw, and sugar cane bagasse and energy crops such as switchgrass into fermentable sugars.[29]
Cellulose-bearing materials typically also contain other polysaccharides, including hemicellulose. When undergoing hydrolysis, hemicellulose decomposes into mostly five-carbon sugars such as xylose. S. cerevisiae, the yeast most commonly used for ethanol production, cannot metabolize xylose. Other yeasts and bacteria are under investigation to ferment xylose and other pentoses into ethanol.[30]
On January 14, 2008, General Motors announced a partnership with Coskata, Inc. The goal is to produce cellulosic ethanol cheaply, with an eventual goal of US$1 per U.S. gallon ($0.30/L) for the fuel. The partnership plans to begin producing the fuel in large quantity by the end of 2008. In June 2009, this goal is still ahead of the firm. By 2011 a full-scale plant will come on line, capable of producing 50 to 100 million gallons of ethanol a year (200–400 ML/a).[31]
[edit] Prospective technologies
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Ethanol plant in Turner County, South Dakota
The anaerobic bacterium Clostridium ljungdahlii, discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including synthesis gas, a mixture of carbon monoxide and hydrogen that can be generated from the partial combustion of either fossil fuels or biomass. Use of these bacteria to produce ethanol from synthesis gas has progressed to the pilot plant stage at the BRI Energy facility in Fayetteville, Arkansas.[32] The BRI technology has been purchased by INEOS.
Another prospective technology is the closed-loop ethanol plant.[33] Ethanol produced from corn has a number of critics who suggest that it is primarily just recycled fossil fuels because of the energy required to grow the grain and convert it into ethanol. There is also the issue of competition with use of corn for food production. However, the closed-loop ethanol plant attempts to address this criticism. In a closed-loop plant, renewable energy for distillation comes from fermented manure, produced from cattle that have been fed the DDSG by-products from grain ethanol production. The concentrated compost nutrients from manure are then used to fertilize the soil and grow the next crop of grain to start the cycle again. Such a process is expected to lower the fossil fuel consumption used during conversion to ethanol by 75%.[34]
Though in an early stage of research, there is some development of alternative production methods that use feed stocks such as municipal waste or recycled products, rice hulls, sugarcane bagasse, small diameter trees, wood chips, and switchgrass.[35]
[edit] Testing
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Infrared reflection spectra of liquid ethanol, showing the -OH band centered at ~3300 cm−1 and C-H bands at ~2950 cm−1.
Breweries and biofuel plants employ two methods for measuring ethanol concentration. Infrared ethanol sensors measure the vibrational frequency of dissolved ethanol using the CH band at 2900 cm−1. This method uses a relatively inexpensive solid state sensor that compares the CH band with a reference band to calculate the ethanol content. The calculation makes use of the Beer-Lambert law. Alternatively, by measuring the density of the starting material and the density of the product, using a hydrometer, the change in specific gravity during fermentation indicates the alcohol content. This inexpensive and indirect method has a long history in the beer brewing industry.
[edit] Purification
Main article: Ethanol purification
Ethylene hydration or brewing produces an ethanol–water mixture. For most industrial and fuel uses, the ethanol must be purified. Fractional distillation can concentrate ethanol to 95.6% by volume (89.5 mole%). This mixture is an azeotrope with a boiling point of 78.1 °C, and cannot be further purified by distillation.
Common methods for obtaining absolute ethanol include desiccation using adsorbents such as starch, corn grits, or zeolites, which adsorb water preferentially, as well as azeotropic distillation and extractive distillation. Most ethanol fuel refineries use an adsorbent or zeolite to desiccate the ethanol stream.
In another method to obtain absolute alcohol, a small quantity of benzene is added to rectified spirit and the mixture is then distilled. Absolute alcohol is obtained in the third fraction, which distills over at 78.3 °C (351.4 K).[12] Because a small amount of the benzene used remains in the solution, absolute alcohol produced by this method is not suitable for consumption, as benzene is carcinogenic.[36]
There is also an absolute alcohol production process by desiccation using glycerol. Alcohol produced by this method is known as spectroscopic alcohol—so called because the absence of benzene makes it suitable as a solvent in spectroscopy.
[edit] Grades of ethanol
[edit] Denatured alcohol
Main article: Denatured alcohol
Pure ethanol and alcoholic beverages are heavily taxed, but ethanol has many uses that do not involve consumption by humans. To relieve the tax burden on these uses, most jurisdictions waive the tax when an agent has been added to the ethanol to render it unfit to drink. These include bittering agents such as denatonium benzoate and toxins such as methanol, naphtha, and pyridine. Products of this kind are called denatured alcohol.[37][38]
[edit] Absolute ethanol
Absolute or anhydrous alcohol refers to ethanol with a low water content. There are various grades with maximum water contents ranging from 1% to ppm levels. Absolute alcohol is not intended for human consumption. It may contain trace amounts of toxic benzene if azeotropic distillation is used to remove water.[39] Absolute ethanol is used as a solvent for laboratory and industrial applications, where water will react with other chemicals, and as fuel alcohol. Spectroscopic ethanol is an absolute ethanol with a low absorbance in ultraviolet and visible light, fit for use as a solvent in ultraviolet-visible spectroscopy.[40]
Pure ethanol is classed as 200 proof in the USA, equivalent to 175 degrees proof in the UK system.[41]
[edit] Rectified spirits
Rectified spirit, an azeotropic composition containing 4% water, is used instead of anhydrous ethanol for various purposes. Wine spirits are about 188 proof. The impurities are different from those in 190 proof laboratory ethanol.[42]
[edit] Reactions
For more details on this topic, see Alcohol.
Ethanol is classified as a primary alcohol, meaning that the carbon its hydroxyl group attaches to has at least two hydrogen atoms attached to it as well. Many ethanol reactions occur at its hydroxyl group.
[edit] Ester formation
In the presence of acid catalysts, ethanol reacts with carboxylic acids to produce ethyl esters and water:
RCOOH + HOCH2CH3 → RCOOCH2CH3 + H2O
This reaction, which is conducted on large scale industrially, requires the removal of the water from the reaction mixture as it is formed. Esters react in the presence of an acid or base to give back the alcohol and carboxylic acid. This reaction is known as saponification because it is used in the preparation of soap. Ethanol can also form esters with inorganic acids. Diethyl sulfate and triethyl phosphate are prepared by treating ethanol with sulfur trioxide and phosphorus pentoxide respectively. Diethyl sulfate is a useful ethylating agent in organic synthesis. Ethyl nitrite, prepared from the reaction of ethanol with sodium nitrite and sulfuric acid, was formerly a widely used diuretic.
[edit] Dehydration
Strong acid desiccants cause the dehydration of ethanol to form diethyl ether and other byproducts. If the Temperature of the ethanol being dehydrated exceeds around 160 °C, ethylene will be the main product. Millions of kilograms of diethyl ether are produced annually using sulfuric acid catalyst:
2 CH3CH2OH → CH3CH2OCH2CH3 + H2O (on 120 °C)
[edit] Combustion
Complete combustion of ethanol forms carbon dioxide and water:
C2H5OH + 3 O2 → 2 CO2 + 3 H2O(l);(ΔHc = −1371 kJ/mol[43]) specific heat = 2.44 kJ/(kg·K)
[edit] Acid-base chemistry
Ethanol is a neutral molecule and the pH of a solution of ethanol in water is nearly 7.00. Ethanol can be quantitatively converted to its conjugate base, the ethoxide ion (CH3CH2O−), by reaction with an alkali metal such as sodium:[12]
2 CH3CH2OH + 2 Na → 2 CH3CH2ONa + H2
or a very strong base such as sodium hydride:
CH3CH2OH + NaH → CH3CH2ONa + H2
The acidity of water and ethanol are nearly the same, as indicated by their pKa of 15.7 and 16 respectively. Thus, sodium ethoxide and sodium hydroxide exist in an equilbrium that is closely balanced:
CH3CH2OH + NaOH [pic]CH3CH2ONa + H2O
[edit] Halogenation
Ethanol is not used industrially as a precursor to ethyl halides, but the reactions are illustrative. Ethanol reacts with hydrogen halides to produce ethyl halides such as ethyl chloride and ethyl bromide via an sn2 reaction:
CH3CH2OH + HCl → CH3CH2Cl + H2O
These reactions require a catalyst such as zinc chloride.[23] HBr requires refluxing with a sulfuric acid catalyst.[23] Ethyl halides can, in principle, also be produced by treating ethanol with more specialized halogenating agents, such as thionyl chloride or phosphorus tribromide.[12][23]
CH3CH2OH + SOCl2 → CH3CH2Cl + SO2 + HCl
Upon treatment with halogens in the presence of base, ethanol gives the corresponding haloform (CHX3, where X = Cl, Br, I). This conversion is called the haloform reaction.[44]" An intermediate in the reaction with chlorine is the aldehyde called chloral:
4 Cl2 + CH3CH2OH → CCl3CHO + 5 HCl
[edit] Oxidation
Ethanol can be oxidized to acetaldehyde and further oxidized to acetic acid, depending on the reagents and conditions.[23] This oxidation is of no importance industrially, but in the human body, these oxidation reactions are catalyzed by the enzyme liver alcohol dehydrogenase. The oxidation product of ethanol, acetic acid, is a nutrient for humans, being a precursor to acetyl CoA, where the acetyl group can be spent as energy or used for biosynthesis.
[edit] Uses
[edit] As a fuel
|Energy content of some fuels compared with ethanol:[45] |
|Fuel type |MJ/L |MJ/kg |Research |
| | | |octane |
| | | |number |
|Dry wood (20% moisture) | |~19.5 | |
|Methanol |17.9 |19.9 |123 |
|Ethanol |21.2[46] |26.8[46] |113[47] |
|E85 |25.2 |33.2 |105 |
|(85% ethanol, 15% gasoline) | | | |
|Liquefied natural gas |25.3 |~55 | |
|Autogas (LPG) |26.8 |50. | |
|(60% propane + 40% butane) | | | |
|Aviation gasoline |33.5 |46.8 | |
|(high-octane gasoline, not jet fuel) | | | |
|Gasohol |33.7 |47.1 |93/94 |
|(90% gasoline + 10% ethanol) | | | |
|Regular gasoline |34.8 |[48] 44.4 |min. 91 |
|Premium gasoline | | |max. 104 |
|Diesel |38.6 |45.4 |25 |
|Charcoal, extruded |50 |23 | |
Main article: Ethanol fuel
The largest single use of ethanol is as a motor fuel and fuel additive. Brazil has the largest national fuel ethanol industry. Gasoline sold in Brazil contains at least 25% anhydrous ethanol, but blending requirements will be reduced to 20% ethanol for a 90-day period beginning February 1, 2010 by government mandate due to low supplies of the biofuel.[49] The U.S. has used ethanol and gasoline blends up to E85 or 15% gasoline and 85% ethanol.
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USP grade ethanol for laboratory use.
Hydrous ethanol (about 95% ethanol and 5% water) can be used as fuel in more than 90% of new cars sold in the country. Brazilian ethanol production is praised for the high carbon sequestration capabilities of the sugar cane plantations, thus making it a real option to combat climate change.[50]
Ethanol combustion in an internal combustion engine yields many of the products of incomplete combustion produced by gasoline and significantly larger amounts of formaldehyde and related species such as acetaldehyde.[51] This leads to a significantly larger photochemical reactivity that generates much more ground level ozone.[52] These data have been assembled into The Clean Fuels Report comparison of fuel emissions[53] and show that ethanol exhaust generates 2.14 times as much ozone as does gasoline exhaust. When this is added into the custom Localised Pollution Index (LPI) of The Clean Fuels Report the local pollution (pollution that contributes to smog) is 1.7 on a scale where gasoline is 1.0 and higher numbers signify greater pollution. The California Air Resources Board formalized this issue in 2008 by recognizing control standards for formaldehydes as an emissions control group, much like the conventional NOx and Reactive Organic Gases (ROGs).[54]
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Ethanol pump station in São Paulo, Brazil where the fuel is available commercially.
World production of ethanol in 2006 was 51 gigalitres (1.3×1010 US gal), with 69% of the world supply coming from Brazil and the United States.[55] More than 20% of Brazilian cars are able to use 100% ethanol as fuel, which includes ethanol-only engines and flex-fuel engines.[56] Flex-fuel engines in Brazil are able to work with all ethanol, all gasoline or any mixture of both. In the US flex-fuel vehicles can run on 0% to 85% ethanol (15% gasoline) since higher ethanol blends are not yet allowed or efficient. Brazil supports this population of ethanol-burning automobiles with large national infrastructure that produces ethanol from domestically grown sugar cane. Sugar cane not only has a greater concentration of sucrose than corn (by about 30%), but is also much easier to extract. The bagasse generated by the process is not wasted, but is used in power plants as a surprisingly efficient fuel to produce electricity.[citation needed]
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A Ford Taurus "fueled by clean burning ethanol" owned by New York City.
The United States fuel ethanol industry is based largely on corn. According to the Renewable Fuels Association, as of October 30, 2007, 131 grain ethanol bio-refineries in the United States have the capacity to produce 7.0 billion US gallons (26 GL) of ethanol per year. An additional 72 construction projects underway (in the U.S.) can add 6.4 billion gallons of new capacity in the next 18 months. Over time, it is believed that a material portion of the ≈150 billion gallon per year market for gasoline will begin to be replaced with fuel ethanol.[57]
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United States Postal Service vehicle running on E85, a "flex-fuel" blend in Saint Paul, Minnesota.[citation needed]
One problem with ethanol is that because it is easily miscible with water, it cannot be efficiently shipped through modern pipelines, like liquid hydrocarbons, over long distances.[58] Mechanics also have seen increased cases of damage to small engines, particularly the carburetor, attributable to ethanol's increased water retention in fuel over time.[59]
[edit] Alcoholic beverages
Main article: Alcoholic beverage
Ethanol is the principal psychoactive constituent in alcoholic beverages, with depressant effects on the central nervous system. It has a complex mode of action and affects multiple systems in the brain; most notably ethanol acts as an agonist to the GABA receptors.[60] Similar psychoactives include those that also interact with GABA receptors, such as gamma-hydroxybutyric acid (GHB).[61] Ethanol is metabolized by the body as an energy-providing nutrient, as it metabolizes into acetyl CoA, an intermediate common with glucose and fatty acid metabolism, that can be used for energy in the citric acid cycle or for biosynthesis.
Alcoholic beverages vary considerably in ethanol content and in foodstuffs they are produced from. Most alcoholic beverages can be broadly classified as fermented beverages, beverages made by the action of yeast on sugary foodstuffs, or as distilled beverages, beverages whose preparation involves concentrating the ethanol in fermented beverages by distillation. The ethanol content of a beverage is usually measured in terms of the volume fraction of ethanol in the beverage, expressed either as a percentage or in alcoholic proof units.
Fermented beverages can be broadly classified by the foodstuff they are fermented from. Beers are made from cereal grains or other starchy materials, wines and ciders from fruit juices, and meads from honey. Cultures around the world have made fermented beverages from numerous other foodstuffs, and local and national names for various fermented beverages abound.
Distilled beverages are made by distilling fermented beverages. Broad categories of distilled beverages include whiskeys, distilled from fermented cereal grains; brandies, distilled from fermented fruit juices, and rum, distilled from fermented molasses or sugarcane juice. Vodka and similar neutral grain spirits can be distilled from any fermented material (grain or potatoes are most common); these spirits are so thoroughly distilled that no tastes from the particular starting material remain. Numerous other spirits and liqueurs are prepared by infusing flavors from fruits, herbs, and spices into distilled spirits. A traditional example is gin, which is created by infusing juniper berries into a neutral grain alcohol.
In a few beverages, ethanol is concentrated by means other than distillation. Applejack is traditionally made by freeze distillation, by which water is frozen out of fermented apple cider, leaving a more ethanol-rich liquid behind. Ice beer (also known by the German term Eisbier or more specifically as Eisbock) is also freeze-distilled, with beer as the base beverage. Fortified wines are prepared by adding brandy or some other distilled spirit to partially fermented wine. This kills the yeast and conserves some of the sugar in grape juice; such beverages are not only more ethanol-rich, but are often sweeter than other wines.
Alcoholic beverages are sometimes used in cooking, not only for their inherent flavors, but also because the alcohol dissolves hydrophobic flavor compounds, which water cannot.
Just as industrial ethanol is used as feedstock for the production of industrial acetic acid, alcoholic beverages are made into culinary/household vinegar: wine and cider vinegar are both named for their respective source alcohols, while malt vinegar is derived from beer.
[edit] Feedstock
Main article: Chemical derivatives of ethanol
Ethanol is an important industrial ingredient and has widespread use as a base chemical for other organic compounds. These include ethyl halides, ethyl esters, diethyl ether, acetic acid, ethyl amines and to a lesser extent butadiene.
[edit] Antiseptic
Ethanol is used in medical wipes and in most common antibacterial hand sanitizer gels at a concentration of about 62% v/v as an antiseptic. Ethanol kills organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses, but is ineffective against bacterial spores.[62]
[edit] Treatment for poisoning by other alcohols
Ethanol is sometimes used to treat poisoning by other, more toxic alcohols, in particular methanol[63] and ethylene glycol. Ethanol competes with other alcohols for the alcohol dehydrogenase enzyme, lessening metabolism into toxic aldehyde and carboxylic acid derivatives,[64] and reducing one of the more serious toxic effects of the glycols, their tendency to crystallize in the kidneys.
[edit] Solvent
Ethanol is miscible with water and is a good general purpose solvent. It is found in paints, tinctures, markers, and personal care products such as perfumes and deodorants. It may also be used as a solvent in cooking, such as in vodka sauce.
[edit] Historical uses
Before the development of modern medicines, ethanol was used for a variety of medical purposes. It has been known to be used as a truth drug (as hinted at by the maxim "in vino veritas"), as medicine for depression and as an anesthetic.[citation needed]
Ethanol was commonly used as fuel in early bipropellant rocket (liquid propelled) vehicles, in conjunction with an oxidizer such as liquid oxygen. The German V-2 rocket of World War II, credited with beginning the space age, used ethanol, mixed with 25% of water to reduce the combustion chamber temperature.[65][66] The V-2's design team helped develop U.S. rockets following World War II, including the ethanol-fueled Redstone rocket, which launched the first U.S. satellite.[67] Alcohols fell into general disuse as more efficient rocket fuels were developed.[66]
[edit] Pharmacology
Ethanol binds to acetylcholine, GABA, serotonin, and NMDA receptors.[68]
The removal of ethanol through oxidation by alcohol dehydrogenase in the liver from the human body is limited. Hence the removal of a large concentration of alcohol from blood may follow zero-order kinetics. This means that alcohol leaves the body at a constant rate, rather than having an elimination half-life.
Also, the rate-limiting steps for one substance may be in common with other substances. For instance, the blood alcohol concentration can be used to modify the biochemistry of methanol and ethylene glycol. In this way the oxidation of methanol to the toxic formaldehyde and formic acid in the (human body) can be prevented by giving an appropriate amount of ethanol to a person who has ingested methanol. Note that methanol is very toxic and causes blindness and death. A person who has ingested ethylene glycol can be treated in the same way.
[edit] Drug effects
Pure ethanol will irritate the skin and eyes. Nausea, vomiting and intoxication are symptoms of ingestion. Long term use by ingestion can result in serious liver damage.[69] Atmospheric concentrations above one in a thousand are above the European Union Occupational exposure limits.[69]
[edit] Short-term
Main article: Short-term effects of alcohol
|BAC (g/L) |BAC |Symptoms[70] |
| |(% v/v) | |
|0.5 |0.05% |Euphoria, talkativeness, relaxation |
|1 |0.1 % |Central nervous system depression, nausea, possible vomiting, |
| | |impaired motor and sensory function, impaired cognition |
|>1.4 |>0.14% |Decreased blood flow to brain |
|3 |0.3% |Stupefaction, possible unconsciousness |
|4 |0.4% |Possible death |
|>5.5 |>0.55% |Death |
[edit] Effects on the central nervous system
Ethanol is a central nervous system depressant and has significant psychoactive effects in sublethal doses; for specifics, see effects of alcohol on the body by dose. Based on its abilities to change the human consciousness, ethanol is considered a psychoactive drug.[71] Death from ethyl alcohol consumption is possible when blood alcohol level reaches 0.4%. A blood level of 0.5% or more is commonly fatal. Levels of even less than 0.1% can cause intoxication, with unconsciousness often occurring at 0.3–0.4%.[72]
The amount of ethanol in the body is typically quantified by blood alcohol content (BAC), which is here taken as weight of ethanol per unit volume of blood. The table at right summarizes the symptoms of ethanol consumption. Small doses of ethanol generally produce euphoria and relaxation; people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgment. At higher dosages (BAC > 1 g/L), ethanol acts as a central nervous system depressant, producing at progressively higher dosages, impaired sensory and motor function, slowed cognition, stupefaction, unconsciousness, and possible death.
More specifically, ethanol acts in the central nervous system by binding to the GABA-A receptor, increasing the effects of the inhibitory neurotransmitter GABA (i.e. it is a positive allosteric modulator).[73]
Prolonged heavy consumption of alcohol can cause significant permanent damage to the brain and other organs.[74] See Alcohol consumption and health.
In America, about half of the deaths in car accidents occur in alcohol-related crashes.[75] The risk of a fatal car accident increases exponentially with the level of alcohol in the driver's blood.[76] Most drunk driving laws governing the acceptable levels in the blood while driving or operating heavy machinery set typical upper limits of blood alcohol content (BAC) between 0.05% and 0.08%.[citation needed]
Discontinuing consumption of alcohol after several years of heavy drinking can also be fatal. Alcohol withdrawal can cause anxiety, autonomic dysfunction, seizures and hallucinations. Delirium tremens is a condition that requires people with a long history of heavy drinking to undertake an alcohol detoxification regimen.
[edit] Effects on metabolism
Main articles: Ethanol metabolism and Alcohol dehydrogenase
Ethanol within the human body is converted into acetaldehyde by alcohol dehydrogenase and then into acetic acid by acetaldehyde dehydrogenase. The product of the first step of this breakdown, acetaldehyde,[77] is more toxic than ethanol. Acetaldehyde is linked to most of the clinical effects of alcohol. It has been shown to increase the risk of developing cirrhosis of the liver,[61] multiple forms of cancer, and alcoholism.
[edit] Drug interactions
Ethanol can intensify the sedation caused by other central nervous system depressant drugs such as barbiturates, benzodiazepines, opioids, phenothiazines and anti-depressants[72]
[edit] Magnitude of effects
[pic]
[pic]
Most significant of the possible long-term effects of ethanol. Additionally, in pregnant women, large consumption causes fetal alcohol syndrome.
Some individuals have less-effective forms of one or both of the metabolizing enzymes, and can experience more-severe symptoms from ethanol consumption than others. Conversely, those who have acquired alcohol tolerance have a greater quantity of these enzymes, and metabolize ethanol more rapidly.[78]
[edit] Long-term
Main article: Long-term effects of alcohol
[edit] Birth defects
Ethanol is classified as a teratogen. See fetal alcohol syndrome.
[edit] Other effects
Frequent drinking of alcoholic beverages has been shown to be a major contributing factor in cases of elevated blood levels of triglycerides.[79]
Ethanol is not a carcinogen.[80][81] However, the first metabolic product of ethanol, acetaldehyde, is toxic, mutagenic, and carcinogenic.
[edit] Natural occurrence
Ethanol is produced naturally from the fermentation of overripe fruit by yeasts.[82] Despite many reports to the contrary, there is little scientific evidence that animals seek out overripe fruit for its intoxicating effects; rather, it suggests that they instead actively avoid doing so.[83] Ethanol is also produced during the germination of many plants as a result of natural anerobiosis.[84] Ethanol has been detected in outer space, forming an icy coatinthanol, a type of alcohol, has been getting a lot of attention as an alternative fuel for vehicles. It's produced domestically, it's a renewable resource, and it's cost-competitive with other fuels. However, ethanol plants create some problems. Ethanol production consumes enormous quantities of water, the plants have been accused of creating air pollution, and it affects the corn markets, driving up the price of food.
Air Pollution
The United States Environmental Protection Agency (EPA) has accused several ethanol producers of compliance problems with air quality standards. Making ethanol industrially creates air pollutants such as volatile organic compounds, sulfur dioxide and carbon monoxide. The EPA has taken legal action against ethanol producers found in violation of the Clean Air Act.
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Water Consumption
According to a report by Sea Stachura of Minnesota Public Radio, ethanol plants use large amounts of water to process corn into alcohol. Three gallons of water are consumed for every gallon of ethanol produced. One Minnesota plant used 146 million gallons of water in 2005, enough for a small city. While the better plants clean and recycle water for their own reuse, local governments must closely monitor the plants' water consumption.
Food Prices
While you can make ethanol from several different biological sources, ethanol plants currently use corn for the majority of the fuel they produce. In a paper published by the University of Wisconsin, authors T. Randall Fortenbery and Hwanil Park analyzed the effects of the use of corn by ethanol plants and found it increases the price for corn. Since corn sees use in many food products, including indirectly as beef, this makes many of the foods you see at the supermarket more expensive.
Read more:
g thanol, a type of alcohol, has been getting a lot of attention as an alternative fuel for vehicles. It's produced domestically, it's a renewable resource, and it's cost-competitive with other fuels. However, ethanol plants create some problems. Ethanol production consumes enormous quantities of water, the plants have been accused of creating air pollution, and it affects the corn markets, driving up the price of food.
Ethanol is produced biologically by fermenting sugar with Saccharomyces yeasts. Under anaerobic (meaning in the absence of oxygen) conditions, when yeast metabolize sugar, they produce ethanol and carbon dioxide. Bioethanol (meaning ethanol production derived from crops) is the most common renewable fuel today and is derived from corn grain (starch) and sugar cane (sucrose) [1]. Thus, ethanol is an inherently renewable eco-friendly resource, contributing nothing in itself to greenhouse gases. However, a study published in the journal Environmental Science & Technology (ES&T) concludes that if every vehicle in the U.S. ran on ethanol-based fuel, the number of respiratory-related deaths and hospitalizations would likely increase.
You read that right, widespread use of E85 would likely result in an increase in respiratory-related deaths and hospitalizations.
Stanford University atmospheric chemist Mark Z. Jacobson, author of the study said [2]:
“Ethanol is being promoted as a clean and renewable fuel that will reduce global warming and air pollution, but our results show that a high blend of ethanol poses an equal or greater risk to public health than gasoline, which already causes significant health damage.”
Jacobson used a sophisticated 3-D atmospheric computer model that accounted for the transport of tailpipe emissions across the U.S. along with chemical and radiative transformations in the atmosphere – key components that have been neglected in previous studies. He combined the ambient concentrations with health effects and population data to simulate air quality in the year 2020, when ethanol-powered vehicles are expected to be widely available in the U.S. He then determined the health risks due to gasoline and ethanol, and analyzed the results at high resolution in Los Angeles and at lower resolution in the entire U.S.
Jacobson explained that:
“… chemicals that come out of a tailpipe are affected by a variety of factors, including chemical reactions, temperatures, sunlight, clouds, wind and precipitation. In addition, overall health effects depend on exposure to these airborne chemicals, which varies from region to region. Ours is the first ethanol study that takes into account population distribution and the complex environmental interactions.”
The results
The study results show that converting to E85 (85% ethanol, 15% gasoline) could result in higher ozone-related asthma, hospitalization and mortality. The death rate increases about 9% in Los Angeles and 4% in the U.S. over projected death rates with gasoline vehicles.
E85 vehicles reduced atmospheric levels of two carcinogens, benzene and butadiene, but increased two others, acetaldehyde and formaldehyde. As a result, cancer rates for E85 are likely to be similar to those for gasoline. In some parts of the country (Los Angeles and the Northeast), E85 use was projected in increase ozone levels. The oxidant ozone is a well-known air pollutant. According to the Environmental Protection Agency (EPA), ozone inhalation is associated with respiratory tract inflammation and functional alterations of the lung [3]. The increased levels of ozone were partially offset by decreased levels in the Southeast. Nonetheless, future E85 use may be a greater overall public health risk than gasoline. Jacobson concludes that E85 is unlikely to improve air quality over future gasoline vehicles and that unburned ethanol emissions from E85 may result in a global-scale source of acetaldehyde larger than that of direct emissions.
Brazil
Brazil is the only country in the world where a large-scale ethanol fuel program, introduced in 1979, has been implemented. By 1997, approximately 4 million Brazilian automobiles ran on neat ethanol (100% ethanol) and another 9 million ran on an ethanol-gasoline blend (22% ethanol) [4]. Since the introduction of ethanol fuel in Brazil, several studies on air quality have been conducted that confirm Jacobson’s recent projections.
In 1990, the concentration of ambient acetaldehyde was determined to be the most abundant carbonyl in three major cities of Brazil [5]. Indeed, acetaldehyde concentrations in urban areas of Brazil were substantially higher than concentrations measured elsewhere in the world, and was thought to be the result of large-scale ethanol fuel use. A more recent study measuring the ambient concentrations of up to 61 carbonyls in Rio de Janeiro found that the most abundant were formaldehyde and acetaldehyde [6]. The authors ranked measured carbonyls with respect to ozone formation potential and reaction with OH and found that ozone formation is dominated by formaldehyde (43% of total) followed by acetaldehyde (32%).
Health effects
In children, repeated short-term exposure to ozone may damage developing lungs and may lead to permanent reductions in lung function [7]. Indeed, time spent outside in areas of high ozone is associated with a higher incidence of asthma than areas of low ozone. Adults exposed to ozone exhibit impaired lung function and irritative lower airway symptoms [8]. Ozone exposure has been associated with an increased number of hospital admissions [9-12]
Alternative alternatives
E85 clearly has it’s advantages: in addition to the potential carbon savings and reduced impact on global warming, E85 can be distributed and dispensed like conventional liquid fuel and can be used in vehicles that cost automakers very little in terms of additional cost. However, although I am all for decreased dependence on fossil energy, it shouldn’t come at the expense of our health.
There are alternatives, including hybrid technology and biodiesel.
In a recent interview with NPR, former Chrysler chairman Lee Iacocca said that the Big Three American automakers (General Motors Corporation, Ford Motor Company and Chrysler) lost their dominance because they failed to “follow-the-market”.
At the end of the interview, he said:
” … I’ve become real fan in the past year of plug-in hybrids. That’s the wave of the future.”
Plug-in hybrids – a third alternative. You can listen to Iacocca’s interview with NPR here.
References
1. Gray et al. Bioethanol. Curr Opin Chem Biol. 2006 Apr;10(2):141-6. Epub 2006 Mar 7.
View abstract
2. Ethanol Vehicles Pose Significant Risk to Health, New Study Finds. Stanford Report. 2007 Apr 18.
3. Ozone and Your Patient’s Health, Course Summary & Key Points. Air Pollution Training Institute, Environmental Protection Agency.
4. Grosjean D. Atmospheric Chemistry of Alcohols. J. Braz. Chem. Soc. 1997; 8(4): 433-42.
5. Grosjean et al. Urban Air Pollution in Brazil: Acetaldehyde and Other Carbonyls. Atmospheric Environment 1990 24B: 101-106.
6. Grosjean et al. Speciated ambient carbonyls in Rio de Janeiro, Brazil. Environ Sci Technol. 2002 Apr 1;36(7):1389-95.
View abstract
7. McConnell et al. Asthma in exercising children exposed to ozone: a cohort study. Lancet. 2002 Feb 2;359(9304):386-91.
View abstract
8. Bromberg and Koren. Ozone-induced human respiratory dysfunction and disease. Toxicol Lett. 1995 Dec;82-83:307-16.
View abstract
9. Medina-Ramon et al. The effect of ozone and PM10 on hospital admissions for pneumonia and chronic obstructive pulmonary disease: a national multicity study. Am J Epidemiol. 2006 Mar 15;163(6):579-88. Epub 2006 Jan 27.
View abstract
10. Lee et al. Association between air pollution and asthma admission among children in Hong Kong. Clin Exp Allergy. 2006 Sep;36(9):1138-46.
View abstract
11. Chang et al. Air pollution and hospital admissions for cardiovascular disease in Taipei, Taiwan. Environ Res. 2005 May;98(1):114-9.
View abstract
12. Yang et al. Association between ozone and respiratory admissions among children and the elderly in Vancouver, Canada. Inhal Toxicol. 2003 Nov;15(13):1297-308.
View abstract
Tags: acetaldehyde, air quality, alternative fuel, bioethanol, E85, Eco-Friendly, ethanol, ethanol fuel, greenhouse gases, ozone, ozone-exposure
Ethanol is a very high octane fuel, replacing lead as an octane enhancer in gasoline.
Fuels that burn too quickly make the engine "knock". The higher the octane rating, the slower the fuel burns, and the less likely the engine will knock.
When ethanol is blended with gasoline, the octane rating of the petrol goes up by three full points, without using harmful additives.
Adding ethanol to gasoline "oxygenates" the fuel, adding oxygen to the fuel mixture so that it burns more completely and reduces polluting emissions such as carbon monoxide.
Ethanol and ETBE oxygenator, made from ethanol, are much safer than the toxic and polluting MTBE fossil-fuel-derived oxygenator used by oil companies.
Ethanol (ethyl alcohol, grain alcohol), according to the US Department of Energy's National Renewable Energy Laboratory, is a "clear, colorless liquid with a characteristic, agreeable odor" -- and taste, some would add.
This is the drinkable (though toxic) alcohol, the active ingredient in beer, wine and spirits. Methanol (methyl alcohol, wood alcohol) is much more poisonous and isn't drinkable at all, it kills people.
Ethanol is also a high-performance motor fuel that cuts poisonous exhaust emissions and is better for the environment.
|[pic] |
|The Model T Ford was built to |
|run on ethanol. |
Henry Ford designed the famed Model T Ford to run on alcohol -- he said it was "the fuel of the future". The oil companies thought otherwise, however -- but the oil crisis of the early 1970s gave ethanol fuel a new lease of life.
|[pic] |
|Henry Ford |
The US leads the world in ethanol production (ahead of Brazil), with 7 billion gallons of cleaner, ethanol-blended gasoline used in 2007, about 12% of fuel sales in the US. Most of it is E85 (85% ethanol 15% gasoline) or E10 (10% ethanol 90% gasoline), which most gasoline cars can use without engine conversion.
Ethanol blends are increasingly used in South Africa, while Brazil, the world's ethanol fuel success story, produces four billion gallons of ethanol a year. All Brazilian fuel contains at least 24% ethanol, and much of it is 100% ethanol. Many other countries are implementing ethanol fuel programs.
Chrysler, Ford, and General Motors all recommend ethanol fuels, and nearly every car manufacturer in the world approves ethanol blends in their warranty coverage.
More than two trillion miles have been driven on ethanol-blended fuels in the US since 1980.
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|California, 2007, 594p. |
|[pic] |
|David Blume's book is the new |
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What is ethanol?
Ethanol is made by fermenting and then distilling starch or sugar crops such as sugar-cane, maize, sorghum, wheat and other grains, or even cornstalks, fruit and vegetable waste.
The benefits
Ethanol is a much cleaner fuel than petrol (gasoline):
• It is a renewable fuel made from plants
• It is not a fossil-fuel: manufacturing it and burning it does not increase the greenhouse effect (see Greenhouse gases and global warming)
• It provides high octane at low cost as an alternative to harmful fuel additives
• Ethanol blends can be used in all petrol engines without modifications
• Ethanol is biodegradable without harmful effects on the environment
• It significantly reduces harmful exhaust emissions
• Ethanol's high oxygen content reduces carbon monoxide levels more than any other oxygenate: by 25-30%, according to the US EPA
• Ethanol blends dramatically reduce emissions of hydrocarbons, a major contributor to the depletion of the ozone layer
• High-level ethanol blends reduce nitrogen oxide emissions by up to 20%
• Ethanol can reduce net carbon dioxide emissions by up to 100% on a full life-cycle basis
• High-level ethanol blends can reduce emissions of Volatile Organic Compounds (VOCs) by 30% or more (VOCs are major sources of ground-level ozone formation)
• As an octane enhancer, ethanol can cut emissions of cancer-causing benzene and butadiene by more than 50%
• Sulphur dioxide and Particulate Matter (PM) emissions are significantly decreased with ethanol.
Backyard ethanol
As with biodiesel, you don't have to be a corporation to make ethanol -- you can make fuel alcohol in your backyard, and many people are doing just that, and running their vehicles on clean-burning alcohol instead of gasoline.
It's more equipment-intensive than biodiesel. You need a still, and you need to learn how to ferment beer. You can build your own still, and there's good information available to help you learn what you need to know.
You'll find everything you need in our Resources section and in the Biofuels Library.
Permits: In the US, home brewers need to get a "small fuel producer" permit from the US Alcohol and Tobacco Tax and Trade Bureau (TTB).
How does it work?
Ethanol is a very high octane fuel, replacing lead as an octane enhancer in gasoline.
Fuels that burn too quickly make the engine "knock". The higher the octane rating, the slower the fuel burns, and the less likely the engine will knock.
When ethanol is blended with gasoline, the octane rating of the petrol goes up by three full points, without using harmful additives.
Adding ethanol to gasoline "oxygenates" the fuel, adding oxygen to the fuel mixture so that it burns more completely and reduces polluting emissions such as carbon monoxide.
Ethanol and ETBE oxygenator, made from ethanol, are much safer than the toxic and polluting MTBE fossil-fuel-derived oxygenator used by oil companies.
Production
Ethanol fuel production is a good locally-based industry, providing local jobs and a market for local materials, and helping to keep money and investment within the community. That's why so many of the farming states in the US (and Canada) back ethanol fuel.
One ethanol plant owned by farmers in Minnesota processes 11,751 bushels of grain a day to produce 33,990 gallons of ethanol and 95 tons of high-protein livestock feed.
If you happen to have a spare acre in your back yard, you can raise enough maize to make enough ethanol to drive even a 17mpg gas-guzzler about 5,000 miles, along with enough animal feed to help keep you in eggs and chicken.
If the climate favours sugarcane, an acre's worth will take you nearly 15,000 miles. A few fruit trees would help a lot too. You could put the by-product in a digester, along with other organic wastes, to produce methane gas for cooking -- or as a heat source for the distillation process.
Alcohol yield tables (for 30 different feedstocks), showing: Average yield of 99.5 percent alcohol per ton; Average yield of 99.5 percent alcohol per acre.
Energy balance
Ethanol is a highly efficient fuel. A study by the Institute of Local Self-Reliance in the US found that using the best farming and production methods, "the amount of energy contained in a gallon of ethanol is more than twice the energy used to grow the corn and convert it to ethanol".
The US Department of Agriculture says each BTU (British Thermal Unit, an energy measure) used to produce a BTU of gasoline could be used to produce 8 BTUs of ethanol.
The non-profit American Coalition for Ethanol says ethanol production is "extremely energy efficient", with a positive energy balance of 125%, compared to 85% for gasoline, making ethanol production "by far the most efficient method of producing liquid transportation fuels".
One of the most controversial issues relating to ethanol (and more recently to biodiesel as well, see below) is what environmentalists call the "net energy" of ethanol production: is more energy used to grow and process the raw material into ethanol than is contained in the ethanol itself?
It's especially controversial in the US. In the US most ethanol is made from corn (maize), which is far from the best energy crop (Brazil uses sugar cane). Nonetheless, a US Department of Agriculture study concludes that ethanol contains 34% more energy than is used to grow and harvest the corn and distill it into ethanol. "Estimating the Net Energy Balance of Corn Ethanol", by Hosein Shapouri et al., US Department of Agriculture, Economic Research Service, Office of Energy and New Uses, Agricultural Economic Report No. 721, July 1995 -- "Studies conducted since the late 1970s have estimated the net energy value of corn ethanol. However, variations in data and assumptions used among the studies have resulted in a wide range of estimates. This study identifies the factors causing this wide variation and develops a more consistent estimate... We show that corn ethanol is energy efficient as indicated by an energy ratio of 1.24."
"The Energy Balance of Corn Ethanol: An Update", by Hosein Shapouri and James A. Duffield, U.S. Department of Agriculture, Office of Energy Policy and New Uses, and Michael Wang of the Center for Transportation Research, Energy Systems Division, Argonne National Laboratory. Agricultural Economic Report No. 813, 2002: "Corn ethanol is energy efficient... For every BTU dedicated to producing ethanol there is a 34% energy gain... Only about 17% of the energy used to produce ethanol comes from liquid fuels, such as gasoline and diesel fuel. For every 1 BTU of liquid fuel used to produce ethanol, there is a 6.34 BTU gain." Full report (Acrobat file, 176 kb):
In "How Much Energy Does It Take to Make a Gallon of Ethanol?", David Lorenz and David Morris of the Institute for Local-Self Reliance (ILSR) state: "Using the best farming and production methods, the amount of energy contained in a gallon of ethanol is more than twice the energy used to grow the corn and convert it to ethanol." A 1992 ILSR study, based on actual energy consumption data from farmers and ethanol plant operators, found that the production of ethanol from corn is a positive net energy generator. In this updated paper the numbers look even more attractive: more energy is contained in the ethanol and the other by-products of corn processing than is used to grow the corn and convert it into ethanol and by-products.
How_Much_Energy_Does_it_Take_to_Make_a_Gallon_.html
New study confronts old thinking on ethanol's net energy value, 3/28/2005 -- Ethanol generates 35% more energy than it takes to produce, according to a recent study by Argonne National Laboratory conducted by Michael Wang. The new findings support earlier research that determined ethanol has a positive net energy balance, according to the National Corn Growers Association. That research was conducted by USDA, Michigan State University, the Colorado School of Mines, the Institute for Local Self-Reliance and other public and private entities. Argonne is one of the US Department of Energy's largest research centers.
/ag/story/data/agNews_050328crETHANOL.xml&catref=ag1001
Report on the new study :
ArgonneNatlLabEthanolStudy.pdf
A USDA study released in 2004 found that ethanol may net as much as 67% more energy than it takes to produce.
Ethanol under fire: David Pimentel et al
Actually it's Big Ethanol and Big Corn that are under fire by Big Oil, though Big Corn and Big Agriculture are a major client of Big Oil. We tend to think they might all deserve each other. Small is beautiful, especially with food and biofuels, and we don't support Big Ethanol producers like Archer Daniels Midland, Cargill or Monsanto any more than we support ExxonMobil or Shell.
But we don't like disinformation either. The Biofuel mailing list has been outing Cornell University Prof. David Pimentel for five years -- see:
biofuel - Search results for 'pimentel'
And more recently his new ally Tad Patzek of Berkeley:
biofuel - Search results for 'Patzek'
|[pic] |
|See Energy Balance of Corn Ethanol|
|Results -- six charts that show |
|the picture at a glance (Acrobat |
|file, 140 kb) |
In August 2001 Pimentel attacked the economics of corn-to-ethanol production in an article published in the Encyclopedia of Physical Sciences and Technology. Pimentel asserted that ethanol production is uneconomic: "The growers and processors can't afford to burn ethanol to make ethanol. US drivers couldn't afford it, either, if it weren't for government subsidies to artificially lower the price."
"Ethanol fuel from corn faulted as 'unsustainable subsidized food burning' in analysis by Cornell scientist", August 6, 2001 -- "Neither increases in government subsidies to corn-based ethanol fuel nor hikes in the price of petroleum can overcome what one Cornell University agricultural scientist calls a fundamental input-yield problem: It takes more energy to make ethanol from grain than the combustion of ethanol produces."
In a detailed analysis of Pimentel's research, Dr. Michael S. Graboski of the Colorado School of Mines says Pimentel's findings are based on out-of-date statistics (22 year-old data) and are contradicted by a recent US Department of Agriculture (USDA) study.
"Comparison of USDA and Pimentel Net Energy Balances" -- "The USDA analysis clearly shows, contrary to the Pimentel paper, that US farming and ethanol manufacture are very energy efficient, and that the energy content of ethanol delivered to the consumer is significantly larger than the total fossil energy inputs required to produce it. USDA estimates that ethanol facilities produce at least 1.23 units of energy as ethanol for every fossil BTU included considering all energy inputs related to corn farming, corn transport, ethanol production, and distribution and transport of finished ethanol." Full report:
"Pimentel clearly does not understand the economics of ethanol manufacture" -- a full rebuttal, from the US National Corn Growers Association.
Another rebuttal: "Industry Argues That Ethanol Delivers"
In fact this isn't the first time Pimentel had published misinformation about ethanol, nor the first time critics had poked his analyses full of holes. He knows he's using outdated data, but that doesn't stop him. In 1998 he published this report:
"Energy and Dollar Costs of Ethanol Production with Corn" by David Pimentel, April 1998 -- "Ethanol does not provide energy security for the future. It is not a renewable energy source, is costly in terms of production and subsidies, and its production causes serious environmental degradation."
This report was debunked by, among others, Michael Wang and Dan Santini of the Center for Transportation Research, Argonne National Laboratory, who conducted a series of detailed analyses on energy and emission impacts of corn ethanol from 1997 through 1999:
"Corn-Based Ethanol Does Indeed Achieve Energy Benefits" -- "Prof. David Pimentel's 1998 assessment of corn ethanol concluded that corn ethanol achieved a negative energy balance (which is usually defined as the energy in a product minus energy used to produce the product). Unfortunately, his assessment lacked timeliness in that it relied on data appropriate to conditions of the 1970s and early 1980s, but clearly not the 1990s... With up-to-date information on corn farming and ethanol production and treating ethanol co-products fairly, we have concluded that corn-based ethanol now has a positive energy balance of about 20,000 Btu per gallon."
Wang and Santini found that Pimentel had been recycling his already-ancient data for at least 10 years.
In August 2002 a new report from the USDA found that not only is ethanol energy-efficient, it's efficiency is steadily improving.
"Only Dr. Pimentel disagrees with this analysis. But his outdated work has been refuted by experts from entities as diverse as the USDA, DOE, Argonne National Laboratory, Michigan State University, and the Colorado School of Mines. While the opponents of ethanol will no doubt continue to peddle Pimentel's baseless charges, they are absolutely without credibility," the Renewable Fuels Association commented.
"From stalk to fuel tank, ethanol a net energy gain" -- Washington, August 7, 2002, Reuters: Measured from cornfield to the fuel tank, ethanol provides more energy than is consumed in producing it, researchers said in a new report that could figure in congressional debate over U.S. energy policy.
The Renewable Fuels Association report on the study:
Full report (Acrobat file, 176 kb):
Biofuels: Energy Balance, Environmental and Energy Study Institute, October, 2003 -- ... A 2002 study by the US Department of Agriculture that accounts for gasoline and diesel fuel use, fertilizers and a variety of other energy inputs in the production, concluded that the energy balance of ethanol is 1.34:1. This means that ethanol "yields 34% more energy than it takes to produce it, including growing the corn, harvesting it, transporting it and distilling it into ethanol." These data are consistent with a study by Dr. Bruce Dale, Michigan State University (2002), and a study by Argonne National Laboratory (1999).
Energy%20Balance%20update.htm
Energy Balance/Life Cycle Inventory for Ethanol, Biodiesel and Petroleum Fuels, Minnesota Department of Agriculture -- ... "The finished liquid fuel energy yield for fossil fuel dedicated to the production of ethanol is 1.34 but only 0.74 for gasoline. In other words the energy yield of ethanol is (1.34/0.74) or 81 percent greater than the comparable yield for gasoline."
Pimentel's arguments
Under the heading "Food Versus Fuel Issues", Pimentel writes that "expanding ethanol production could entail diverting essential cropland from producing corn needed to sustain human life to producing corn for ethanol factories." He says corn is "a human-food resource" and adds: "Present food shortages throughout the world call attention to the importance of continuing US exports of corn and other grains for human food to reduce malnutrition and starvation. Increased corn exports... most importantly help feed people who need additional food for their survival."
But as Pimentel should surely know, most US corn is used for feeding animals, not hungry people -- 76% of the corn used in the US is used for animal feed. Twenty percent of the total US corn crop is exported; two-thirds of these exports go directly to the wealthy industrial OECD countries, mostly to feed animals.
Less than three-tenths of one percent of total US corn exports went to the 25 poorest countries in 1996. More US corn goes to make alcoholic beverages in the US than is exported to feed the hungry in the world's 25 most undernourished countries combined.
The Energetics of Ethanol: An Introduction and Link to Studies by David Morris, Institute for Local Self-Reliance -- Does it take more energy to make ethanol than is contained in ethanol? That question continues to haunt the ethanol industry even after 27 years of expanding production. Over the years more than 20 scientific studies have examined the question. This document contains links to the major studies of the subject completed during the last decade.
MSU Ethanol Energy Balance Study, May 2002. Independent study by Michigan State University MSU shows that there is 56% more energy in a gallon of ethanol than it takes to produce it. "The available energy from ethanol is much higher than the input energy for producing ethanol. In other words, using ethanol as a liquid transportation fuel would significantly reduce domestic use of petroleum even in the worstcase scenario." 288kb Acrobat file:
Ethanol Can Contribute to Energy and Environmental Goals, Alexander E. Farrell, Richard J. Plevin, Brian T. Turner, Andrew D. Jones, Michael O’Hare, Daniel M. Kammen, SCIENCE, Vol. 311, 27 Jan. 2006: "Studies that reported negative net energy incorrectly ignored coproducts and used some obsolete data. All studies indicated that current corn ethanol technologies are much less petroleum-intensive than gasoline but have greenhouse gas emissions similar to those of gasoline." 180kb Acrobat file:
Pimentel published further reports attacking the ethanol energy balance in 2003 and again in 2005, this time accompanied by Tad Patzek of the University of California, Berkeley. This time they attacked biodiesel as well, which is firmly established as energy-efficient, even biodiesel from soybean monocrops grown by the usual fossil-fuel intensive industrial agriculture methods.
Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower, David Pimentel and Tad W. Patzek, Natural Resources Research, Vol. 14, No. 1, March 2005 (C 2005). 116kb Acrobat file.
News release from Cornell University, July 5, 2005: "Cornell ecologist's study finds that producing ethanol and biodiesel from corn and other crops is not worth the energy."
Pimentel still used the antiquated data from his 1979 study. Some insight into Patzek's bias against ethanol can be found on his own website: .
Patzek worked for Shell Oil Company as a researcher, consultant, and expert witness. He founded and directs the UC Oil Consortium, which is mainly funded by the oil industry at the rate of US$60,000-120,000 per company per year.
See Energy Balance of Corn Ethanol Results -- six charts that show the picture at a glance (Acrobat file, 140 kb)
New study confronts old thinking on ethanol's net energy value, 3/28/2005 -- Ethanol generates 35% more energy than it takes to produce, according to a recent study by Argonne National Laboratory conducted by Michael Wang. The new findings support earlier research that determined ethanol has a positive net energy balance, according to the National Corn Growers Association. That research was conducted by USDA, Michigan State University, the Colorado School of Mines, the Institute for Local Self-Reliance and other public and private entities. Argonne is one of the US Department of Energy's largest research centers.
/ag/story/data/agNews_050328crETHANOL.xml&catref=ag1001
Report on the new study :
ArgonneNatlLabEthanolStudy.pdf
A USDA study released in 2004 found that ethanol may net as much as 67% more energy than it takes to produce.
Regarding the energy balance of biodiesel, see, eg:
Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus -- A Joint Study Sponsored by: U.S. Department of Agriculture and U.S. Department of Energy Final Report May 1998. 1.8 Mb Acrobat file:
An Overview of Biodiesel and Petroleum Diesel Life Cycles, Sheehan, Camobreco, Duffield, Graboski, Shapouri, National Renewable Energy Laboratory of the U.S. Department of Energy, Midwest Research Institute, May 1998. 655kb Acrobat file:
gen/19980501-gen-203.pdf
How Much Energy Does It Take To Make A Gallon of Soydiesel? by David Morris, Irshad Ahmed and John Decker, 15-Feb-05, 1.5Mb Acrobat file:
How_Much_Energy_Does_It_Take_To_Make_A_Gallon_.pdf
"The Pimentel/Patzek study uses outdated information on agricultural practices as well as unrealistic and unsubstantiated assumptions regarding energy inputs. At least eight other peer-reviewed studies that have been conducted over the past 12 years find exactly the opposite, that biodiesel has a highly positive energy balance. This new study is not convincing and does not represent a significant contribution or advance in this area of energy research." -- Dr. Robert McCormick, US DOE National Renewable Energy Laboratory, in National Biodiesel Board, DOE, USDA Officials Dispute Biofuels Study: Pimentel/Patzak study deeply flawed, researchers say, NBB, July 21, 2005. 36kb Acrobat file:
20050721_pimentel_response.pdf
Energy Balance of Biodiesel
Units of energy produced for 1 unit of energy consumed *
- Petroleum 0.88 units produced
- Ethanol 1.62 units produced
- Soy Biodiesel 3.24 units produced
*USDA
|[pic] |
|Minnesota Department of Agriculture |
See also Food or Fuel?
What standard farm?
The energy in-energy out life-cycle studies use a standard farm as the production model. Such a thing as a standard farm may exist as a statistical average, but a "standard" farming procedure is a myth even on industrialised farms. Anyway, industrial farming has about as much future as the cheap fossil fuels it depends on so heavily, it's hardly a suitable model for sustainable biofuels production.
What would these models have to do with a homesteader who has a good supply of waste wood to burn and no better way of using it, plus a large supply of past-their-use-by-date cakes from a bread factory that he's rescuing from the waste stream? (An actual case.) The cakes could go to a pig farm instead, but they don't. There are many such niches -- spoiled fruit from farms that ought to have pigs but don't, and so on and on. Such factors never get calculated.
What would it have to do with this? "We are looking at a very interesting integrated distillery approach being developed by the Brazilians, where instead of going for the large 300,000 litres per day plants, a fully integrated approach is taken with a 1,500 ha area, farmed by small growers, and feeding sugarcane and sweet sorghum into a 20,000 litres per day plant, with cattle feedlots at the distillery, the manure going into [biogas] digesters with the stillage, producing enough energy for the distillery, leaving the bulk of the bagasse to be used for power generation to supply the surrounding areas." (Energy projects in Africa.)
See also Bio-regional energy -- India's Talukas.
Once you start looking at the local level and at integrated approaches to crop production and wastes, and include energy production and use, a different picture emerges that leaves these broad generalisations without much meaning.
A sustainable mixed farm can produce all its own fuel, with much or possibly all of it coming from crop by-products and waste products without any dedicated land use, and with very low input levels.
Biofuels production only makes real sense when the fuel is used as close as possible to where the crop is grown. It makes no sense to waste energy trucking crops long distances to a centralised Big Biofuels plant and then wasting even more energy trucking it all the way back again. The Fuel Miles issue is the same as the Food Miles issue.
See also How much fuel can we grow? How much land will it take?
There's yet another way of looking at it. This is from Offgrid-Online, April 5, 2000.
"Will we get out more energy than we put in? Does it matter? Generally a scheme that did not create more energy than it consumed would be useless, but in this case we might have a different view. Since we are after a portable fuel, we might be willing to spend more energy to get it, so long as we used a non-portable fuel to do so. For example, suppose we use wood-fired heat to make alcohol. Wood is a poor fuel as far as portability in general is concerned and is nearly useless for internal combustion engines. [But see Woodgas -- JtF] So what if we have to spend 2 BTUs of wood heat for each BTU of alcohol fuel produced? That might still be a good deal if we had lots of wood and gasoline was (that is, continues to be) highly priced."
The Sierra Club, among other "green" organisations in the US, has a different objection to ethanol. They see the whole issue as clouded by the high levels of nitrogen fertilisers used to grow the maize, and the eco-damage the N-runoff causes.
But that's an objection to US factory farming, not to ethanol. In a more rational system there's no need for nitrogen fertilisers, and no loss of yield through not using them.
One 15-year study found that organic farming is not only kinder to the environment than "conventional", intensive agriculture but has comparable yields of both products and profits. The study showed that yields of organic maize are identical to yields of maize grown with fertilisers and pesticides, while soil quality in the organic fields dramatically improves. (Drinkwater, L.E., Wagoner, P. & Sarrantonio, M. Legume-based cropping systems have reduced carbon and nitrogen losses. Nature 396, 262–265.) These findings are widely corroborated. See, eg: The case for organics -- Scientific studies and reports
It seems strange that an organisation like the Sierra Club doesn't know about organic farming, or pretends not to. But then they're still fighting diesels.
See also Food or Fuel?
Question: What are the Benefits of Using Ethanol?
Ethanol is a relatively low-cost alternative fuel, but what are the benefits of using ethanol or an ethanol blend in place of unblended gasoline?
Answer: Using ethanol as an alternative to gasoline provides several key benefits.
Ethanol is good for the environment
Overall, ethanol is considered to be better for the environment than gasoline. Ethanol-fueled vehicles produce lower carbon monoxide and carbon dioxide emissions, and the same or lower levels of hydrocarbon and oxides of nitrogen emissions.
E85, a blend of 85 percent ethanol and 15 percent gasoline, also has fewer volatile components than gasoline, which means fewer emissions from evaporation.
Adding ethanol to gasoline in lower percentages, such as 10 percent ethanol and 90 percent gasoline (E10), reduces carbon monoxide emissions from the gasoline and improves fuel octane.
Ethanol is widely available and easy to use
Flexible fuel vehicles that can use E85 are widely available and come in many different styles from most major auto manufacturers. E85 is also widely available at a growing number of stations throughout the United States.
Flexible fuel vehicles have the advantage of being able to use E85, gasoline, or a combination of the two, giving drivers the flexibility to choose the fuel that is most readily available and best suited to their needs.
Ethanol is good for the economy
Ethanol production supports farmers and creates domestic jobs. And because ethanol is produced domestically, from domestically grown crops, it reduces U.S. dependence on foreign oil and increases the nation’s energy independence
Question: How is Ethanol Made?
Answer: Ethanol can be made from any crop or plant that contains a large amount of sugar or components that can be converted into sugar, such as starch or cellulose.
As their names imply, sugar beets and sugar cane contain natural sugar. Crops such as corn, wheat and barley contain starch that can be easily converted to sugar. Most trees and grasses are made of cellulose, which can also be converted into sugar, although not as easily as starch.
Most ethanol is produced using a four-step process:
1. The ethanol feedstock (crops or plants) are ground up for easier processing;
2. Sugar is dissolved from the ground material, or the starch or cellulose is converted into sugar;
3. Microbes feed on the sugar, producing ethanol and carbon dioxide as byproducts; and
4. The ethanol is purified to achieve the correct concentration.
It is also possible to produce ethanol through a wet-milling process, which is used by many large ethanol producers. This process also yields byproducts such as high-fructose corn syrup, which is used as a sweetener in many prepared foods.
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