To start the dry milling process , the entire corn kernel (or other starchy grain) is ground into flour. This flour is called a “meal” because it was created without separating any parts of the corn kernel. Water and enzymes are added to the meal, making it a “mash.” The enzymes in the mash break down the starch and turn it into a simple sugar, dextrose. Then, ammonia is added to the mash which provides nutrients to the yeast and serves as a pH control.
Dry Milling is the most common ethanol production method in the United States. Dry milling for cement is the least intensive method for producing ethanol. Though this process requires less energy,it also creates fewer byproducts. Dried distiller’s grains with solubles (DDGS) are one of the byproducts from dry cement milling; dried distiller’s grains are sold to cattle farmers for feed. Wet stillage, another form of livestock feed, is another byproduct from the dry milling process. However, it cannot be stored for as long as dried distiller’s grains. Carbon dioxide (CO2) is the last byproduct from dry milling. Soda companies often buy this byproduct to use for carbonation in their beverages.
Mining and milling methods The mash is moved into a high temperature cooker to reduce bacteria levels and prepare the mash for fermentation. Once cooled, the mash is combined with yeast in the fermenters. Yeast converts the simple sugar, dextrose, into ethanol and carbon dioxide (CO2). During fermentation the mash is agitated, to keep the yeast evenly spread throughout the mash, and it is cooled to maintain the ideal temperature for the yeast. 40 to 50 hours later, the fermentation process is completed.