Acetic acid is available for the formation of acetyl coenzyme A, which enters the Krebs cycle and is eventually metabolized to carbon dioxide and water. The enzymatic oxidation of ethanol occurs primarily in the liver, first to acetaldehyde by the enzyme alcohol dehydrogenase and then conversion to acetic acid by the enzyme aldehyde dehydrogenase. Since rapid absorption occurs in the small intestine, factors that delay or enhance gastric emptying will influence the rate of absorption of ethanol into the blood. Nancy Linde, in Encyclopedia of Toxicology (Second Edition), 2005 ToxicokineticsĮthanol absorption through the stomach wall is minimal. These flexible fuel (or flex-fuel) vehicles are discussed in Section 4. Auto manufacturers began in 1997 to produce cars and pickup trucks that could use either ethanol or gasoline. Departments of Energy and Agriculture, ethanol-fueled vehicle production is increasing. In the United States, because of support from corn-growing states and the U.S. h In sugarcane-origin ethanol plants, there is no fossil fuel consumption in the plant (all fuel consumed in the plant is sugarcane bagasse, the by-product of sugarcane crushing) fossil fuel consumption corresponds to the agricultural phase and fertilizer production. g Considering the coproduction of corn oil and animal feed products, the allocation of energy inputs corresponds to 1096 kcal/liter of ethanol. d Includes bagasse surplus production (Brazil) see footnote b. c Final energy balance corresponds to the low energy content in 1 liter of ethanol divided by the total fossil fuel consumption to produce 1 liter of ethanol. b Fossil fuel consumption in ethanol production corresponds to diesel oil use in the agricultural phase and during transport, to coal and natural gas use in corn-based ethanol plants, and to natural gas use for fertilizer production. Ethanol can also be produced from cellulose feedstock (corn stalks, rice straws, sugarcane bagasse, etc.), through a process still under development.įossil fuel consumption in ethanol production (MJ/liter of ethanol) bĪ Lower ethanol energy value: 21.2 MJ/liter. Table II shows a comparison of the ethanol energy balance in Brazil (from sugarcane) and the United States (from corn). In the United States, ethanol is produced from corn and represents a large consumption of fossil fuels, with much lower energy balance, despite the existing controversy among specialists. This is due not only to high agricultural and industrial productivity levels, but also to the extremely favorable energy balance of the alcohol production. Because ethanol in Brazil is produced from sugarcane, it has the lowest production cost in the world. Anhydrous ethanol has lower and higher heating values of 21.2 and 23.4 megajoules (MJ)/liter, respectively for gasoline the values are 30.1 and 34.9 MJ/liter. Ethanol's flammability in air is also much lower than that of gasoline, which reduces the number and severity of vehicle fires. These two principal areas will be considered in detail.Įthanol makes an excellent motor fuel: it has a motor octane number that exceeds that of gasoline and a vapor pressure that is lower than that of gasoline, which results in lower evaporative emission. It is this distinction that governs the main areas of application required for ethanol determination, namely measuring concentration levels in alcoholic beverages of all types and measuring blood ethanol levels in humans after the consumption of alcoholic beverages. Ethanol poisoning normally results from the consumption of liquid ethanol in alcoholic beverages rather than from inhalation. However, as ethanol is readily oxidized in the body to water and carbon dioxide, it is not an accumulative poison. Concentrations in excess of these values soon become intolerable, causing severe coughing and laceration. The compound is reported to be detectable by nose at ∼350 ppm, while higher levels of ∼5000–10000 ppm can cause irritation to the eyes and mucous membranes of the upper respiratory tract. However, flammability is not a serious problem in the industrial environment providing there is reasonable ventilation, which also prevents ethanol from causing severe problems as an industrial poison. Criddle, in Encyclopedia of Analytical Science (Second Edition), 2005 Environmental ConsiderationsĮthanol is a flammable liquid, its vapor concentrations being explosive in the range 3.3–19.0% (v/v) in air.
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