How is Ethanol Made?

The production of ethanol, or ethyl alcohol, from starch-based feedstocks is an excellent example of value-added processing. Using corn as the feedstock is one of the most common ways to produce ethanol. Dry mill ethanol production is a premier manufacturing production system to extract starch contained in the corn.

Ethanol plants are fermentation facilities in which corn is ground and mixed with water to form a mash. Mash is then heated, and enzymes are added to convert starch into fermentable sugars. Fermentation then occurs when yeast is added to convert the sugars into ethanol and carbon dioxide.

Fermentation produces a mixture called “beer” containing about 15% ethanol and 85% water. “Beer” is boiled in a distillation column to remove the water, which results in ethyl alcohol that is 90% to 95% pure. This mixture is then dehydrated, which increases the alcohol content to 99% or more. At this point the product is mixed with a denaturant for commercial sale, which renders the product unfit for human beverage consumption.

Solids removed during the distillation process are centrifuged and/or evaporated and then sent to a dryer system to reduce the moisture content to approximately 10%. This value-added co-product is DDGS (distiller’s dried grain with solubles). DDGS is the corn kernel minus the starch.

What is biodiesel?

Biodiesel is the name of a clean burning alternative fuel, produced from domestic, renewable resources. Biodiesel contains no petroleum, but it can be blended at any level with petroleum diesel to create a biodiesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Biodiesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics.

Biodiesel can be made from variety of vegetable oils and animal fats (e.g., recycled cooking greases). It can be blended with diesel, resulting in lower GHG emissions.

Through a process called transesterification, methanol with sodium hydroxide is mixed with the oil, or reduced fat, letting the by-product glycerine settle. Glycerine can be used in products such as soap. The other component, biodiesel, can be mixed with petroleum-diesel in a combination of ratios (ie. 20% biodiesel, 80% petro is called B20). Fuel-grade biodiesel must be produced to strict industry specifications (ASTM D6751) in order to insure proper performance.

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