What is Feedstock Milling in an Ethanol Plant?

Feedstock milling refers to the mechanical process of grinding or crushing raw feedstock into smaller particles to prepare it for conversion into ethanol. There are two different types of milling to accomplish this: Dry Milling and Wet Milling.

What are the Types of Feedstock Milling?

Dry Milling

The entire grain kernel is ground and processed to produce ethanol, CO2 and distillers grains (DDGS). Additionally, a majority of U.S. ethanol plants use this milling process.

Wet Milling

In wet milling the grain is soaked and separated into components, such as starch, fiber, germ, and gluten, before fermentation. Thus, this allows for co-product recovery (i.e. corn oil and corn gluten).

Why is Milling Needed?

The three main reasons that it is needed is because it increases surface area, facilitates downstream processing, and improve yield.

Increase Surface Area

By breaking down the grain, milling increases the surface area available for enzymes to act on during the liquefaction and saccharification steps. Thus, improving the efficiency of starch conversion into fermentable sugars.

Facilitate Downstream Processing

The milling process reduces particles to the proper particle size. Thus, ensuring better mixing with the water and enzymes, improvements to heat transfer, and reduces clumping in the slurry.

Improve Yield

Efficient milling results in more complete starch conversion which leads to higher ethanol yields.

Conclusion

Milling is a critical first step in the ethanol production process that prepares the grain for enzymatic hydrolysis and fermentation. It directly impacts the plant’s efficiency and output. Therefore, if you are looking for more information on ethanol plants and how they operate, stay tuned as over the course of the next few weeks more blog posts will be released.