What are the Main Steps in the Ethanol Process?

Ken Black

The steps in the ethanol process depend in part on the type of milling procedure in place. Dry milling is the simpler process, but wet milling offers the chance to use the grain to produce other products. Whether wet or dry milling, the basic ethanol process will convert grain to ethyl alcohol, from which the term ethanol is derived. The raw material is delivered, fermented, distilled, and then mixed with another product, usually gasoline. It is then ready for delivery.


In wet milling for corn-based ethanol, there are some extra steps necessary at the beginning of the ethanol process. The major step includes allowing the corn to soak in a mixture of water and sulfurous acid. This helps separate the corn starch from the rest of the material. Once the starch has been separated, the process then becomes very similar to dry milling, and there is no difference in the quality of the ethanol produced.

Potatoes can provide starch for ethanol.
Potatoes can provide starch for ethanol.

After the starch is delivered in wet milling, or after the raw material is delivered in dry milling, the ethanol process begins with grinding it into very fine particles. It is then mixed with water to produce a mash. This mash is later cooked to reduce the amount of bacteria present.

Once the mash has been cooked, it is put into the fermenter. There, yeast and microbes are added that will help begin the fermentation process. The microbes feed on the sugar, which produces the alcohol, or ethanol, and carbon dioxide in a process that usually takes at least 50 hours. The carbon dioxide may be released or captured for other processes, depending on how the ethanol plant is set up.

After the ethanol has been produced through the fermentation process, the next step involves distilling the liquid. This part of the ethanol process will make the alcohol content nearly 100%, or 200 proof. At this point, it could also be provided as a very potent alcohol drink, and there have been reports of those working at ethanol plants becoming intoxicated by the product.

Due to the fact that it can be consumed by humans, another step is often added to the ethanol process. This is usually the mixing in of gasoline. Though more gasoline will be added once it reaches its destination, adding just a little — usually 5% — at the plant will render the product unsuitable to be consumed by humans. Doing this avoids subjecting the ethanol to the beverage alcohol tax.

Ethanol is often derived from corn starch.
Ethanol is often derived from corn starch.

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