Production of Ethanol
How is ethanol produced?
Ethanol is an alternative fuel fermented from corn, grains or agricultural waste. Its primary use is to supplement gasoline. It is plant based therefore what is used could be regrown. The best part is that it reduces ozone forming emissions. Although it is more corrosive than gasoline it is less toxic. It is less volatile than gasoline therefore reducing the chance of explosion.
Producers in Brazil use sugar cane to start the process. In the U.S. it is made from corn and but the production varies, from using sugar containing plant materials such as potatoes and wheat barley.
The production starts by milling the corn into small particles. Cornstarch is exposed which is used in the fermentation process. It is then removed and crushed into a fine powder that is mixed with water and alpha-amylase. Alpha-amylase is an enzyme used to break up the powder into even smaller particles. The resulting mash is then cooked anywhere from 120 to 150 degrees. This is done to liquefy the starch and reduce the level of bacteria. It is then heated to 225 degrees to help break it down even further. It is then removed from cookers and cooled. Glucoamylase is another enzyme added to convert the liquid starch into dextrose that can then be fermented. The puree is mixed with yeast which will change the sugar to ethanol and carbon dioxide. It takes about 48 hours for it to ferment. It is then heated to the point where ethanol vaporizes. The vapor is cooled and collected where it will condense and return to a liquid state. It is then passed through a dehydration system that will purify it and remove any excess water. At this stage the ethanol is known as anhydrous ethanol and it is about 200 proof. A small amount anywhere from 2 to 5 percent of gasoline is added which is a requirement for all fuel-grade ethanol. What's leftover is saved and used. The grain is used as livestock feed and the carbon dioxide is collected, purified, and compressed. It is then sold and used by the carbonated beverage and dry-ice industries.
The production of ethanol from starch is among man's earliest undertaking into value added processing. While the basics remain the same the process has been refined in recent years leading to an efficient process. There are two processes to the production of ethanol they are dry and wet milling. The main difference is the initial treatment of the grain. The process described above is dry milling. In the process using wet milling the grain is initially soaked in water and dilute sulfurous acid for 24 to 48 hours.
