Technology – How is E85 Ethanol Made?

5 05 2009

GM – Education – Grades 9-12 – Fuels and Energy – How is E85 ethanol made

Most of the ethanol in the U.S. is made from corn, which contains a starch that can easily be converted into sugar. Other forms of ethanol come from grains, wheat, barley or potatoes. Brazil, the world’s largest ethanol producer, makes the fuel from sugarcane. Ethanol can also be produced from cellulosic biomass such as trees, Sawgrass or grasses.

The process

ethanol is primarily produced by a process called dry grinding in which the starch portion of corn is fermented into sugar, and then distilled into alcohol. The process takes about 48 hours.

Dry grinding begins by inserting corn through a hammer mill that smashes the corn into flour. The flour then runs through a collection of screens to create a fine powder called meal.

The meal is placed into tanks where it is mixed with water. This mixture, now called mash, passes through steamers that help break apart the starch molecules and enters the liquefaction process, where enzymes — proteins that help break down the mash — are introduced to begin fermentation.

During fermentation, yeast is added to the mash to convert the sugars into carbon dioxide(which is often collected, compressed, and sold for use in other industries) and a product called beer, which consists of 12-15 percent ethanol.

The beer then enters the distillation process, where it will pass through a series of towers heated to 170 degrees to help purify the mixture, making it 190 proof (meaning that it is 95 percent ethanol), leaving only water and distiller’s grain as bi-products. The grain is sold as feed for livestock. The ethanol factory reuses the water.

After this process, the mixture passes though what are called molecular sieves. These sieves resemble little BB pellets with holes in the middle. Any remaining water in the mixture is absorbed by the sieves, allowing only pure ethanol to pass though. The result is 100% ethanol.

Finally, the ethanol that will be used for fuel must be denatured, or made unfit for human consumption, by adding a small amount of gasoline. The denatured ethanol is then transported to a fuel factory where it is blended with gasoline to create the fuel needed for your vehicle — E85, which consists of 85 percent ethanol and 15 percent gasoline.




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