Ethanol Production Process
Grain Handling

1. We have three 595,000-bushel grain bins.
2. These three bins hold about 42 days of corn supply for United Ethanol.
3. The unloading pit is designed to move 30,000 bushels per hour.
4. The plant grinds about 45,000 bushels per day.
5. The two 500-hp hammermills grind the corn into flour before going into the plant.
Photo: grain unloading pit
Cooking and Mashing

1. Flour is mixed with water, backset, and enzymes to begin the first step of the process.
2. The mixture is heated to 185 degrees F to kill any bacteria that may be present. This is called the cooking step.
3. The cooked mash is held in a tank to allow complete liquafaction of the mixture.
4. The mash is then cooled and pumped into the fermenters.

Photo: cooking and mashing


1. We have three fermenters with a capacity of 760,000 gallons each.
2. Yeast is added to the mash in the fermenter to start the fermentation process.
3. The yeast converts the simple sugars to alcohol. During this process, CO2 is released, captured, and liquefied for sale.
4. The mash ferments for about 46-52 hours, at which time it's pumped to the beerwell.
5. At this point, the mash -- which contains around 15-16 percent alcohol by volume -- is referred to as beer.

Photo: fermentation alley

Control Room

1. All processes throughout the plant are controlled via a computerized control system located in the control room.
2. Most processes are controlled automatically and overseen by the shift supervisor.
3. Manual process changes will be made by the two shift operators.
Photo: Eric Norby in the control room

1. The beer is then pumped to a three-column distillation unit which strips all the alcohol from the beer.
2. The stripped alcohol at this point is about 186-190 proof which is still not fuel grade, even though it will burn by itself.
3. This "low" proof alcohol is then run through a process called the molecular sieves.
4. This process removes the remaining water at the molecular level via a dessicant style reaction.
5. The alcohol at this point is pure and is 200 proof.
6. This alcohol is then pumped to the tank farm where it is denatured (made unfit for human consumption) and made ready for shipment.

Photo: beer column, stripper column, and rectifier column


1. The boilers produce steam which is used to heat the various processes. The boilers are rated at 150 psi and 2200 boiler horsepower.
2. The main use of steam is in distillation and evaporation where the alcohol is stripped from the beer and the water is evaporated from the thin stillage.
3. Most of this energy is reused in the processes by preheating fluids going into the process and cooling the fluids leaving, thus increasing the efficiency of the plant.
4. The backup generator is rated at 3200 hp.

Photo: boilers

Dehydration and Evaporation
  1. The liquid mixture that is left over from distillation after the alcohol is stripped out is called thick stillage.
    2. The thick stillage is sent to centrifuges which spin out the solids.
    3. Two streams come out of the centrifuges. One is the solids which are called wet distiller's grain (WDG) and the other is thin stillage.
    4. The WDG is sent to the ring dryer to be dried into dried distiller's grain (DDG) or can be sent to a seperate pad to be sold as WDG.
    5. The thin stillage stream is sent to evaporators which evaporates the water out of the stillage and concentrating the solids content.
    6. The concentrated product is called syrup. This syrup can be sold directly as a feed additive or will be mixed back into the wetcake going to the dryer to be dried into DDG.
    7. In January, 2011, United Ethanol placed its corn oil extraction system (COES) into operation. The COES system extracts corn oil from the syrup coming from the evaporators. This high-value co-product is sold to biodiesel manufacturers or as an animal-feed additive. Extraction of the oil from the syrup also enhances the quality and flowability of the DDG and provides yet another revenue stream to United Ethanol.
    8. The evaporated water is condensed and recycled back into the cook process at the front of the plant. In addition, a portion of the thin stillage is also recycled back into the cook process. This is called backset. In this manner, the plant is able to reuse the same water and liquid over and over again in the process.
    9. United Ethanol produces 380-440 tons of DDG per day.
    Photo: ring dryer
Product Storage 

1. The alcohol will be stored in the two product storage tanks located in the tank farm. These tanks offer a capacity of 490,000 gallons each.
2. The DDG is stored in a flat storage shed.

Photo: ethanol tank farm