Technology

The traditional Dry-Grind Process grinds the whole Corn Kernel and mixes it with Water and Enzymes. The Mash is then cooked to liquefy the Starch further. The Mash is then cooled and mixed with more Enzymes to convert the remaining Sugar Polymers to Glucose before Fermenting to Ethanol. The Components of the Kernel not Fermented include the Germ, Fiber, and Protein, and are concentrated in the Distillers Dried Grains that are produced as Co-products. While Dry Milling is less capital intensive, it also yields less Ethanol per Bushel of Corn than Wet Milling.^[1]

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^[2]:

• 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^[2].

On average, 1 Bushel of Corn (56 pounds) processed by a Dry Mill Ethanol Biorefinery produces^[2]:

• 2.9 gallons of Denatured Fuel Ethanol
• 15.1 pounds of Distiller Grains Animal Feed (10% Moisture)
• 0.9 pounds of Corn Distillers Oil
• 16 pounds of captured, biogenic Carbon Dioxide

References

1. Cole Gustafson, Jason Fewell, Dry versus Wet Grind Processing, North Dakota State University

2. Krysta Levac, 13 Aug 2018, How is Ethanol Made?, letstalkscience.ca