How is ethanol made?
Ethanol has been made for hundreds of years!
It's true! Ethanol has been used in one form or another for a long time. Actually, its first recorded use was in 15th century Scotland to make moonshine whiskey. Fast forward a few hundred years and we have become very efficient at making large quantities of ethanol to help supply a portion of our fuel needs with a (mostly) renewable resources. Have you ever wondered how ethanol is made? We did and our science class took the time to make our own ethanol because SCIENCE!!!
Note: We are showing the steps to make ethanol from corn. There are many other products that can be used to make ethanol such as cellulose, sugar cane, or wood fibers, but this is the most widely used process in America.
Step 1: Grain delivery and storage.
It all begins with the local farmer. They have to plant, fertilize, raise, and harvest the corn before our journey even starts with converting corn to a useful fuel. Then it is delivered to the local ethanol plant where it is cleaned of any foreign material and stored for when it is needed. Our local ethanol plant can store three million bushels which is enough for about 20 days of operation. They use 150,000 bushels, or approximately 125 semi loads of corn per day seven days a week for ethanol production.
Step 2: Grinding
ninety percent of all ethanol plants in America are operated with a dry milling process. The dry milling process is more efficient for ethanol production than the wet milling process. This is mainly due to the lower amount of water needed, and that all available sugars are available for the production of ethanol. Corn is ground up into a fine powder that looks similar to flour. This is done to break the tough outer coating of the corn kernel which will increase the surface area of the starch, which is the main ingredient, and that is what we are really after. Then it is mixed with water. The water is used to help move the product from one tank to another during the production process and to allow the enzymes to interact with the mash. An interesting note is that most of the water is reclaimed from the production process and re-used. This greatly reduces environmental impact and energy requirements.
Step 3: Cooking and Liquefication
This is the first step in breaking down the long starch chains into more simple sugars called glucose that the yeast can work with. There are a couple of things happening here.
First, we increase the temperature of the mash above 140 degrees Fahrenheit. This will cause the starch to hydrolyze or absorb water and begin to break down the long starch chains into shorter sections.
Second, we add an enzyme called a-amylase that will further break down the starch (Are you sensing a trend yet?)
Finally we go through a process called saccharification that uses another enzyme called glucoamylase to (you guessed it) further break down the starches. At this point the starches are broken down into simple sugars called glucose.
Step 4: Fermentation
Let's do a quick recap. We grew the corn and ground it up. Then we broke all of the starches down to glucose. Finally we are ready to make some ethanol.
Ethanol is produced by a process called fermentation. Yeast is added to the mash and over the course of 2-3 days 90-95% of the glucose is broken down into ethanol and C02. The C02 is captured and piped to a local facility that manufactures dry ice for many various industries.
That leaves us with the ethanol, which at this point is at a concentration of approximately 12-15% because it is mixed with the water and mash. Every bushel of corn produces around 2.7-3 gallons of ethanol.
One thing that we found interesting about the fermentation process is that yeast is surprisingly difficult to keep alive. Yeasts survive in specific environments and those environments must be maintained throughout the process. If not they can get sick and die just like us.
Step 5: Distillation
We're getting close to the finish line now. Our ethanol is in there we just need to get it out. We do this by heating the ethanol/water mixture and boiling off the ethanol which has a lower boiling point than water. This gets us to approximately 95% pure ethanol which is still not pure enough for our needs. The problem is that ethanol is hydroscopic, which means that it is attracted to water. It forms very strong bonds with water, which we cannot break simply by heating it.
What's left is the mash. This is dried and resold as DDG's or dried distillers grains with solubles. This is a very valuable feed ingredient for the dairy, poultry, and swine industries
Step 6: Dehydration
Our last step is to make anhydrous ethanol or ethanol without water.
We do this By passing all of the liquid over a molecular sieve. A molecular sieve is a filter that absorbs moisture but does not interact with the ethanol. This brings us to our final point of 99% pure ethanol.
Step 7: Denature
Congratulations, you have finally made ethanol. At this point ethanol is an alcohol that you could drink however it wont taste very good. Ethanol plants are designed for quantity not quality. We have one more step that needs to happen. denaturing is a process of poisoning ethanol so it cannot be drank this allows it to be sold as a fuel which greatly reduces taxes and doesn't require conforming to food grade standards during production. There are many things that can be used as a denaturant but the most common one is gasoline which is added at about a 2% rate.
Step 8: Storage and Delivery
Now we are at the end of the line for the ethanol plant. the denatured ethanol is stored in large holding tanks that are tested to meet quality standards before anything is allowed to be sold. once the fuel is certified it is transported to refineries by truck or rail car where it is mixed with gasoline to arrive at our E10, E15, E30, or E85 ethanol blends,