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Ethanol Production Process

Ethanol is commercially produced using either a wet mill or dry mill process. Wet milling involves separating the grain kernel into its component parts (germ, fiber, protein, and starch) prior to fermentation. ICM-designed plants utilize the dry mill process, where the entire grain kernel is ground into flour. The starch in the flour is converted to ethanol during the fermentation process, creating carbon dioxide and distillers grain.

Learn more about the Dry Mill Process when you mouse over the steps.

Grain Receiving

Grain is delivered by truck or rail to the ethanol plant where it’s loaded in storage bins designed to hold enough grain to supply the plant for 7–10 days.


The grain is screened to remove debris, then milled into ground material to allow water and enzymes to contact and to react with starch in the ground material.

Slurry Tanks

In slurry tanks, the ground material is mixed with recycled water and enzymes.  The contact and reaction of these components cause starch gelatinization.

Selective Milling Technology™ (SMT™) (Bolt-On Option)

The slurry flows through a separation device, where solids are selectively separated and ground further in a mechanical milling device, and then returned to the process stream.

Primary Liquefaction

In liquefaction tanks, the process hydrolyzes the gelatinized starch into glucose to produce mash.

Simultaneous Saccharification Fermentation

The glucoamylase enzyme breaks down the dextrins to form simple sugars. Yeast is added to convert the sugar to ethanol and carbon dioxide. The mash is then allowed to ferment for 50–60 hours, resulting in a mixture that contains about 15% ethanol as well as the solids from the grain and added yeast.


The fermented mash is pumped into a multi-column distillation system where additional heat is added. The columns utilize the differences in the boiling points of ethanol and water to boil off and separate the ethanol. By the time the product stream is ready to leave the distillation columns, it contains about 95% ethanol by volume (190-proof). The residue from this process, called stillage, contains non-fermentable solids and water and is pumped out from the bottom of the columns into the centrifuges.

Molecular Sieves

The 190-proof product stream is pumped into the molecular sieve system. These specialized tanks contain molecular sieve beads that adsorb water molecules from the process stream while ethanol molecules pass through unaffected. When the product stream leaves the molecular sieves, it contains approximately 99% ethanol by volume (200 proof).


Before the ethanol is sent to the storage tanks, a small amount of denaturant is added, making it unfit for human consumption.

Ethanol Storage

Most ethanol plants' storage tanks are sized to allow storage of 7-10 days of production capacity.


The stillage from the bottom of the distillation columns contain solids from the grain and added yeast, as well as liquid from the water added during the process. It's then sent and separated through the centrifuges into thin stillage (a liquid with 5-10% solids) and wet distillers grain.


The liquid that is not routed back to the cook/slurry tanks is sent through a multiple-effect evaporation system where it is concentrated into syrup containing 25-50% solids.

Syrup Tanks

The syrup, which is high in protein and fat content, is then mixed back in with the wet distillers grain. 

Grain Drying

The wet cake is conveyed to dryers where it is converted into a low-moisture (10-12%) product called dried distillers grains with solubles.

Bio-Oil Recovery  (Bolt-On Options) 

Base Tricanter System™:  Separates oil from the post-fermentation syrup stream as it leaves the evaporators. The oil is routed to settling tanks, and the remaining concentrated syrup is routed to your plant's existing syrup tank.  

Advanced Oil Recovery™ Skid: Breaks the emulsion concentrate (a mixture of water, oil, soluble proteins, sugars, and starches), dramatically increasing the volume of oil recovered from the plant's process stream.

Settling Tanks

The bio-oil is then pumped to settling tanks where majority of residual solids and wax-bound oil have settled out and pumped to another tank. Then, high quality bio-oil in the settling tanks is transported via tanker trucker or rail.



















































































Cellulosic Ethanol

ICM begins 1,000-hour cellulose switchgrass campaign

ICM officially began a 1,000-hour, fully-integrated switchgrass campaign to prove out its patent-pending Generation 2.0 co-located cellulose to ethanol process on March 12, 2015. Prior to starting this effort, ICM solved significant process challenges in feedstock handling and pretreatment unit operations that are crucial to the commercial success of any cellulose-to-ethanol process. In the process of finding workable solutions to implement its Generation 2.0 process that uses cellulosic feedstocks such as switchgrass, energy sorghum, and corn stover, ICM identified how to effectively mill feedstocks, conveyed them to the conversion process, and pumped them into and through the pretreatment reactor without excessive equipment wear and process line fouling. These challenges were not insignificant. At one point, some equipment parts were failing in less than 48 hours due to the abrasive nature of these feedstocks. ICM has also determined how to efficiently separate the unconverted part of the feedstock from the sugar-containing liquid prior to being fermented into ethanol.

Why is this important?

This allows ICM to make a high-value, single-cell protein animal feed co-product from its fermentation yeast as part of its Generation 2.0 process. ICM is the only cellulosic technology that makes an animal feed co-product as part of its cellulosic technology process. ICM’s process is based on a co-location philosophy that integrates facilities and process operations of a corn ethanol plant and a cellulosic ethanol plant to achieve synergies that improve efficiencies of operations in both plants as shown below.


What is important about 1,000 hours of continuous run time? To commercialize a new, untested technology that could require a $200 - $250 million investment, is financially very risky. A successful 1,000-hour, fully-integrated process campaign will qualify ICM’s technology for federal loan guarantee programs that take a large part of the financial risk out of initial investments. Conducting two separate 1,000-hour integrated process campaigns are a key part of ICM’s current contract with the DOE. One integrated campaign will be conducted with switchgrass as feedstock and the other one will be conducted with energy sorghum as feedstock. Although the process outputs are cellulosic ethanol, single-cell protein animal feed, and a solid fuel for combustion as a renewable supplement to coal-fired power plants, ICM’s primary product from these campaigns is to generate data. The data will be used to provide inputs into a techno-economic computer model that will be used to show commercial economic viability under various market conditions with actual operating data. This helps mitigate risk for ICM’s customers. ICM looks forward to updating its progress of this important piece of development work that leads ICM to the commercialization of ICM’s Generation 2.0 cellulosic ethanol technology.

ICM has already proven its Generation 1.5 Grain Cellulose to Ethanol™ process technology (Gen 1.5) in 1,200-hour and 500-hour, fully-integrated process campaigns in 2012 and 2013, respectively, as shown below. ICM’s Gen 1.5 technology gives corn ethanol plants the ability to convert the cellulosic embedded in corn kernel fiber to cellulosic ethanol. This will allow plants to increase the yield of ethanol produced from a bushel of corn by up to 10%, generate D3 RINS based on cellulosic ethanol production, increase starch conversion, and increase distillers corn oil recovery. This technology is already available for commercial sale.


Research & Development

50 associates on staff including 30 scientists and Five Ph.D.s. with 200+ years of experience.

It’s no wonder ICM's research and development team leads the biofuels industry in developing game-changing equipment and process technologies. Using their combined knowledge of chemistry and microbiology—not to mention their unique blend of intelligence, intuition, and ingenuity—our team comes to work every day looking for new, creative ways to make ethanol production more efficient and cost effective for our customers.

Here a just some of the research and development initiatives being conducted at our pilot ethanol facility and state-of-the-art research center in St. Joseph, Missouri.

  • Cellulosic and Next-Generation Ethanol Development
  • Feedstock Handling and Milling
  • Product Recovery
  • Process-Specific Backset
  • Laboratory and Pilot Plant Technology Development
  • Plant Performance Consultation
  • New Technology Evaluation and Assessment
  • New Technology and ICM Process Technology Validation Experience



We believe in the promise of ethanol.

At ICM, Inc., we’re proud to be part of an industry that makes the world a better place:

  • Ethanol is good for your car. Gasoline enriched with ethanol outperforms straight gasoline in many ways, and E10 (10% ethanol) can be used in all cars.
  • Ethanol is good for the environment. Gasoline enriched with 10% ethanol helps protect air quality by reducing harmful tailpipe emissions by 30%.
  • Ethanol is good for your community and country. American ethanol production creates tens of thousands of jobs, revitalizes rural communities, and reduces oil consumption by 600,000 barrels per day … and growing.

What is Ethanol?

Ethanol is ethyl alcohol (C2H6O), a renewable motor fuel made from corn, other high-starch crops, and cellulose.