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Ethanol production uses corn or another starchy grain, water, enzymes, ammonia, and yeast in order to create alcohol. Ethanol, or grain alcohol, has a variety of uses. One of the most common forms is as an alcoholic beverage. However, it can also be used as fuel, feedstock, or in hand sanitizers, as well as in other applications. The process of ethanol production goes back several hundred years. However, as the years have passed, though the basic concept is the same, the overall process has changed.
The first step in ethanol production is to find a starchy or sugar laden agricultural product. Corn is often used, however, wheat, barley, beets, and potatoes can also be used. Those who create ethanol called the original plant material feedstock. Ethanol production can take place in two forms: dry milling or wet milling. The processes are the same except for how the feedstock is treated before the ethanol production process.
In dry milling, once the feedstock is gathered, it is ground into a fine powder called meal. The meal is then mixed with water. The resulting slurry is called mash. The mash is then mixed with enzymes and then taken to a cooker to liquefy the starch and to get rid of any bacteria. Ammonia is added to control the pH and provide nitrogen for the yeast.
Once the mash is cooled, more enzymes are added to help convert the starch into dextrose, a type of sugar that yeast can consume. Then it is sent to fermenters where yeast is added. Yeast eats the sugar in the mash and produces alcohol and carbon dioxide as by-products. Once the fermenting is finished, the resulting “beer” is taken to distillation columns were the ethanol is separated from the stillage. The ethanol is then dehydrated until it is about 200-proof.
In a wet mill process, the feedstock is first steeped in a water and acid solution. This helps to break it down. Then the slurry is ground to separate the germ from the kernel. After this, fiber is removed from the slurry. The slurry is then sent to hydrocyclones to in order to remove the starch. The starch is then free to be converted into sugar and fermented into ethanol.
If the result of ethanol production is to use ethanol for fuel or other uses, ethanol has to go through one other process. It has to be denatured. Denaturing ethanol makes it toxic to humans. Once ethanol is denatured it is used as a fuel additive, for antiseptic use, as well as for other uses. In order to denature ethanol, a bit of some other product, such as natural gasoline, is added.
@Vincenzo -- that's only sort of true. Corn for using as food is much more expensive to grow than corn for ethanol use. Corn that is usually grown for ethanol production is low grade stuff that isn't regarded as safe for human production and there is no way you will find a farmer selling his expensive food grade corn for use in ethanol production because he will lose money.
Only a desperate farmer will sell his expensive corn for ethanol production. It certainly happens, but ethanol can be made from just about any kind of corn. The cheap stuff will do just fine.
In the United States, corn is by far the most common grain used in Ethanol. Why? Because it is cheap and easy to grow in the U.S. The problem with that is that prices for food corn go up as demand for ethanol increases as more corn is converted to use in ethanol production.
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