How Is Ethanol Made?


Quick Answer

Ethanol is an alcohol derived from starch. There are two primary methods for producing ethanol. The first is called dry milling, and the second is called wet milling.

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Full Answer

With the dry milling method, the starchy grain is ground into powder and combined with water and ammonia before being placed into a high-temperature cooker. The cooker reduces the amount of bacteria in the mixture before it is cooled and put into a fermenter. Inside the fermenter, yeast is added to the mixture, at which point it starts to become ethanol. It takes between 40 and 50 hours for the fermentation to finish. Once fermentation is complete, the ethanol is separated from the rest of the mixture.

To create ethanol via the wet milling method, the starchy grain is soaked in a combination of diluted sulfuric acid and water for one to two days. The resulting mixture is filtered through grinders and a series of separators until the starch has been isolated from the rest of the grain. That starch can be fermented and turned into ethanol through a process similar to that of dry milling.

Ethanol can be blended with gasoline and used as fuel in cars. Gas stations typically offer fuel composed of 90 percent gasoline and 10 percent ethanol.

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