11-01-2014, 04:28 PM
Alternative Fuels: Ethanol
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What is ethanol?
GM Commercial
CH3CH2OH
Ethanol is a clean-burning, high-octane fuel that is produced from renewable sources.
At its most basic, ethanol is grain alcohol, produced from crops such as corn.
Since pure 100% ethanol is not generally used as a motor fuel, a percentage of ethanol is combined with unleaded gasoline, to form E10 and E85
E10: 10% ethanol and 90% unleaded gasoline, is approved for use in any US vehicle
E85: 85% ethanol and 15% unleaded gasoline, is an alternative fuel for use in flexible fuel vehicles (FFVs).
How is it made?
Ethanol can be made by fermenting almost any material that contains starch.
Ethanol can be produced from a variety of feedstocks such as sugar cane, bagasse, miscanthus, sugar beet, sorghum, grain, switchgrass, barley, hemp, kenaf, potatoes, sweet potatoes, cassava, sunflower, fruit, molasses, corn, stover , wheat, straw, cotton.
There are two main valuable co-products created in the production of ethanol: distillers grain and carbon dioxide. Distillers grain is used as a highly nutritious livestock feed while carbon dioxide is collected, compressed, and sold for use in other industries.
Fermentation process
During ethanol fermentation, glucose and other sugars in the corn (or sugarcane or other crops) are converted into ethanol and carbon dioxide.
C6H12O6 → 2 C2H5OH+ 2 CO2 + heat
Like any fermentation reaction, the fermentation is not 100% selective, and other side products such acetic acid, glycols and many other products are formed and are need to be removed during the purification of the ethanol. The fermentation takes place in aqueous solution and the resulting solution after fermentation has an ethanol content of around 15%. The ethanol is subsequently purified by a combination of adsorption and distillation techniques.
Energy Balance
Unlike fossil fuel combustion, which unlocks carbon that has been stored for millions of years, use of ethanol results in comparatively lower increases to the carbon cycle.
Ethanol also degrades quickly in water and, therefore, poses a smaller risk to the environment than an oil or gasoline spill.
It takes less than 35,000 BTUs of energy to turn corn into ethanol, while the ethanol offers at least 77,000 BTUs of energy. Thus ethanol has a positive energy balance—meaning the ethanol yields more energy than it takes to produce it.
Impact on air quality
Using ethanol-blended fuel has a positive impact on air quality. By adding oxygen to the combustion process which reduces exhaust emissions—resulting in a cleaner fuel for cleaner air.
Ethanol reduces the emissions of carbon monoxide, VOX, and toxic air emissions:
Since ethanol is an alcohol based product, it does not produce hydrocarbons when being burned or during evaporation thus decreasing the rate of ground level ozone formation.
Impact on economy
In a 1997 study The Economic Impact of the Demand for Ethanol, Northwestern University’s Kellogg School of Management found that:
During ethanol plant construction, approximately 370 local jobs are created.
During ethanol plant operation, up to 4,000 local jobs are created.
Ethanol plant construction creates $60 million to $130 million in additional income.
Ethanol plant operation creates $47 million to $100 million in additional income.
The U.S. Department of Agriculture has concluded that a 100 million gallon ethanol facility could create 2,250 local jobs for a single community. Ethanol production creates domestic markets for corn and adds 4-6 cents a bushel for each 100 million bushels used. Better prices mean less reliance on government subsidy programs not to mention higher income and greater independence for farmers.