<P> In the dry milling process the entire corn kernel is ground into flour and referred to as "meal ." The meal is then slurried by adding water . Enzymes are added to the mash that convert starch to dextrose, a simple sugar . Ammonia is added to control the pH and as a nutrient for the yeast, which is added later . The mixture is processed at high - temperatures to reduce the bacteria levels and transferred and cooled in fermenters . This is where the yeast is added and conversion from sugar to ethanol and carbon dioxide begins . </P> <P> The entire process takes between 40 and 50 hours, during which time the mash is kept cool and agitated in order to facilitate yeast activity . After the process is complete, everything is transferred to distillation columns where the ethanol is removed from the "stillage". The ethanol is dehydrated to about 200 proof using a molecular sieve system and a denaturant such as gasoline is added to render the product undrinkable . With this last addition, the process is complete and the product is ready to ship to gasoline retailers or terminals . The remaining stillage then undergoes a different process to produce a highly nutritious livestock feed . The carbon dioxide released from the process is also utilized to carbonate beverages and to aid in the manufacturing of dry ice . </P> <P> The process of wet milling takes the corn grain and steeps it in a dilute combination of sulfuric acid and water for 24 to 48 hours in order to separate the grain into many components . The slurry mix then goes through a series of grinders to separate out the corn germ . Corn oil is a by - product of this process and is extracted and sold . The remaining components of fiber, gluten and starch are segregated out using screen, hydroclonic and centrifugal separators . </P> <P> The gluten protein is dried and filtered to make a corn gluten - meals co-product and is highly sought after by poultry broiler operators as a feed ingredient . The steeping liquor produced is concentrated and dried with the fiber and sold as corn gluten feed to in the livestock industry . The heavy steep water is also sold as a feed ingredient and is used as an environmentally friendly alternative to salt in the winter months . The corn starch and remaining water can then be processed one of three ways: 1) fermented into ethanol, through a similar process as dry milling, 2) dried and sold as modified corn starch, or 3) made into corn syrup . </P>

What kind of corn is used for ethanol