How Ethanol Is Made

Introduction

Ethanol is a colorless volatile flammable liquid C2H5OH that is the intoxicating agent in liquors and is also used as a solvent called ethyl alcohol or grain alcohol (Meriam 1). C2H5OH is the chemistry components of ethanol; this means ethanol is made of Carbon, Hydrogen, and Hydroxide. Starch or sugar-based feedstock, such as corn, have been used to produce ethanol and ethyl alcohol since the beginning ventures into value-added processing (How Ethanol 1). The value-added process means value is added to producing corn because we now have more valuable uses for the grain. Since natural resources are limited, ethanol provides us with an alternate fuel source. The basic steps to produce ethanol have been refined in the past years, which has lead to a highly efficient process (How Ethanol 1). This analysis explains the steps in producing ethanol from corn.

The steps for producing ethanol are steeping the corn, which involves grinding and/or soaking, and then cooking, fermenting, and distilling the corn. Dry and Wet Milling are the two different ways ethanol can be produced (How Ethanol 1). The initial grain treatment is the major difference between these two processes (How Ethanol 1). In the Dry Mill process, the corn is put through a grinder, cookers, fermenter, distillation columns, and a molecular sieve. In the Wet Mill process, the corn is steeped, put through a starch/gluten separator, and then the starch is fermentated, (refer to the image for dry milling process).

The Process

Dry Mill Ethanol Production

According to the RFA, grinding the complete corn kernel or other starchy grain produces flour, also known as meal. The meal is then processed without separating the different component parts of the grain. Water is mixed with the meal to form a mash to which enzymes are added to convert the mash starch into sugar. Ammonia is also combined to the mash to activate the yeast and control pH balance.

The mash is then put in a high temperature cooker to help keep the bacteria level low before fermentation. The mash is cooled and moved to the fermenters where the addition of yeast produces ethanol and carbon dioxide from the sugar.

During the forty or fifty hour fermentation process, the mash is agitated and kept cool to help the yeast activation. The mash is then transferred to distillation columns where the ethanol is separated from the remaining mash. Conventional distillation methods produce 190 proof ethanol and then dehydration in a molecular sieve produces 200 proof ethanol. With the addition of five percent gasoline, the ethanol is ready to be shipped to gasoline terminals or retailers.

Wet Mill Ethanol Production

The Wet Milling process