orn ethanol plant next to corn field

Corn ethanol plant next to corn field (photosbyjim, iStockphoto)

How is Ethanol Made?

Krysta Levac

Summary

Ethanol is a biofuel that can power a car. Learn about the enzymes, catalysts and processes like fermentation involved in ethanol production.

In many parts of Canada, fields of corn or wheat are common sights. When you see these fields, you might think of food. But these grains are not just for toast and corn flakes anymore. They also end up in Canadians’ fuel tanks, in the form of ethanol. 

Ethanol is a liquid alcohol. It can be used like gasoline in vehicles with internal combustion engines. These engines compress liquid fuel and ignite it with a spark. This creates a combustion reaction, which releases energy. Internal combustion engines capture that energy to power the vehicle. 

Did you know?

There is some evidence that Henry Ford designed the first Model T automobile to run on gasoline, ethanol, or a mixture of the two.

1924–1925 Ford Model T
1924–1925 Ford Model T (Source: LibertyGroup25 [CC BY-SA 3.0] via Wikimedia Commons).

Ethanol is known as a first generation biofuel. This type of fuel is made from sources such as starches, sugars, and vegetable oils. It is produced commercially by breaking down corn and wheat. Ethanol production plants are considered biorefineries. That’s because they convert grain biomass into biofuel using enzymes and living microorganisms.

How is ethanol made?

The input material for making ethanol is called feedstock. Different ethanol production facilities use different feedstock. Facilities in Ontario and Quebec mainly use corn kernels. Facilities in Western Canada mainly use wheat kernels. This is due to the geographical distribution of corn and wheat agriculture in Canada. 

Did you know?

Scientists are looking for ways to use “forest feedstock,” such as wood waste, in the ethanol-production industry. 

The processes are basically the same for corn, wheat and other types of feedstock. Let’s use corn as an example feedstock. 

There are six main steps in the ethanol production process.

Steps in the ethanol production process
Steps in the ethanol production process (© 2019 Let’s Talk Science).

 

Infographic - Text Version

The steps in the ethanol production process include milling the corn to meal, liquefying the meal by adding water and cooking, breaking down starch into sugar, using yeast to ferment the sugar to ethanol, distilling the ethanol by boiling off and condensing it by removing residual water and finally denaturing so that it is undrinkable.

  1. Milling: Whole corn kernels are ground into a form of flour, or meal. The meal is mainly starch. A starch is a carbohydrate made up of long chains of sugar molecules.
  2. Liquefaction: Water is added to the meal to make ‘slurry.’ The slurry is heated to break the long starch molecules into smaller pieces. The enzyme alpha-amylase is added to catalyze (or speed up) the breakdown of the starch molecules.
  3. Saccharification: Starch molecule pieces are broken down into the simple sugar glucose. This reaction is catalyzed by an enzyme called glucoamylase.
  4. Fermentation: Single-celled microorganisms called yeast are added to the slurry. Fermentation is the biochemical process that occurs when yeast break down glucose. Yeast gets energy from glucose. As a result, ethanol is produced.
  5. Distillation and Dehydration: The product of the fermentation process is only 10-15% ethanol. It must be concentrated to become pure (100%) ethanol. Ethanol has a lower boiling point than water. It is selectively evaporated and condensed in a process called distillation. This process produces ethanol that is 95% pure. The remaining 5% of the mixture is water. The mixture is strained and dehydrated to produce pure ethanol.
  6. Denaturation: A small amount of gasoline is added to fuel ethanol to make it undrinkable.  
The main molecules involved in ethanol production
The main molecules involved in ethanol production (Let’s Talk Science using an image from Bacsica via iStockphoto).

There are two main byproducts of corn ethanol production: carbon dioxide (CO2) and distillers’ grains. CO2 is produced by yeast as a byproduct of the fermentation reaction. It is often released into the atmosphere. But it can also be captured and used for other purposes. For example:

  • making carbonated beverages
  • producing dry ice (frozen CO2) to use for cold storage
  • supporting photosynthesis in vegetable greenhouses

Distillers’ grains are the residue from the fermentation tanks. They contain all the non-fermentable components of the corn kernels, plus the added yeast. Distillers’ grains are valuable as a high-protein ingredient in livestock feed.

Ethanol is blended with the gasoline used in our vehicles to produce a more environmentally friendly fuel. The majority of vehicles manufactured after the 1980s can run on a blend of gasoline made up of 10% ethanol (E10). 

Ethanol is a renewable resource. That’s why governments around the world are encouraging people to use ethanol instead of fossil fuels. In Canada, the federal government has a set of guidelines called the Clean Fuel Standards. It encourages people to use fuels with a higher mix of ethanol. 

Some people, on the other hand, have concerns about using ethanol as fuel. For example, there are worries about the amount of energy and land required to grow ethanol feedstock crops. Even with these concerns, ethanol-based fuel is still an important alternative to fossil fuels!

Learn More

How is ethanol made? (2015) 

Video (1:47 min.) from POET Biofuels containing a brief overview of the biofuel making process, from production to distribution.

Ethanol Essentials (2019) 

Web page for the American Coalition for Ethanol with a number of infographics containing information on ethanol production and its benefits .

Fermentation and the preparation of ethanol (2016) 

Video (19:00 min.) from iitutor describing the fermentation process.

References

Clifford, C. B. (n.d.). How corn is processed to make ethanol. Pennsylvania State University.

Grain Farmers of Ontario. (2011, April 26). Food vs. fuel.

Mosier, N. S., & Ileleji, K. (2012). How fuel ethanol is made from corn. Purdue University.

Natural Resources Canada. (2018). Ethanol.