How Ethanol is made:
Ethanol, also known as grain alcohol or ethyl alcohol, is a clear, colorless liquid alcohol often produced by fermenting starches. In Minnesota, ethanol-gasoline blends such as E10 and E85 are produced from corn, but other starch crops may be used for production. Ethanol is a valuable and sustainable alternative to petroleum-based transportation fuels.
While the basic steps remain the same, the ethanol production process has been considerably refined in recent years, leading to a very efficient process. There are two production processes: wet milling and dry milling. The main difference between the two is in the initial treatment of the grain. The Al-Corn plant in Claremont dry mills corn.
Companies are also using biomass gasification and methane digesters to reduce natural gas consumption. Additional work is being done to reduce energy consumption and production costs, increase efficiency and reduce emissions using the best available control technologies. The Al-Corn plant has reduced water consumption to less than 2.5 gallons of water per gallon of ethanol and has eliminated liquid discharge. In addition, energy conservation efforts have reduced the plant’s energy use by more than 25% compared to the original plant design.
Sources: Al-Corn Clean Fuel; Minnesota Department of Agriculture
Aerial view of the Al-Corn Clean Fuel plant in Claremont, MN.
Dry milling – The whole corn kernel is ground into a powder, mixed with water to form a mash (similar to oatmeal) and then cooked with enzymes that turn the starch into glucose. The mash is fermented and distilled to separate the ethanol from the solids and water, which becomes a high quality livestock feed called distillers grains. Many Minnesota plants also produce carbon dioxide, which is used for refrigeration or as an industrial chemical. Dry milling is the most commonly used method in Minnesota.
Wet milling – Corn is steeped in water and sulfur dioxide before grinding, then the germ, fiber, gluten and starch components are separated. The starch can be sold for use in food processing, paper milling and other uses, or, it can be further processed into corn syrup, ethanol, amino acids or a wide variety of other products. The germ, fiber and gluten can be made into corn oil, livestock feed and many other products.