INTRODUCTION
Dry Milling

The dry milling ethanol process (Figure 2) is relatively simple. Corn (or another starch source) is ground, fermented, and the starch converted to ethanol and CO₂. Approximately 1/3 of the dry matter (DM) remains as feed product following starch fermentation, assuming the starch source is approximately 2/3 starch. As a result, all the nutrients are concentrated three-fold because most grains contain approximately 2/3 starch. For example, if corn is 4% oil, the WDGS or DDGS will contain approximately 12% oil. In the dry milling process, the resultant feed co-products are distillers grains, distillers solubles, and distillers grains plus solubles depending on the plant and whether it is producing wet or dry co-products, and the relative amounts of distillers grains and distillers solubles mixed together. If all of the solubles are added back to the grains, DGS are approximately 80% distillers grains and 20% distillers solubles (DM basis) (Corrigan et al., 2007a). Most distillers grains contain some solubles, but this can vary from plant to plant. Solubles are a good source of protein, high in fat, phosphorus (P), and sulfur (S) and low in fiber (Corrigan et al., 2007a). Solubles contain 25% CP, 20% fat, 1.57% P, 0.92% S, and 2.3% neutral detergent fiber (NDF). Distillers solubles have become a popular base for liquid feed supplements. As molasses prices have increased, liquid supplement companies are using wet milling industry steep and dry milling distillers solubles in place of molasses for liquid supplements. In addition, solubles may replace corn and protein in finishing diets (Trenkle, 1997b). Steers fed 4 or 8% of diet DM as corn distillers solubles had improved feed conversion compared to steers fed a conventional cracked corn diet.

The wet milling industry is more complex than dry milling in that the corn kernel is divided into more components for higher value marketing in wet milling. For example, the oil is extracted and sold in the wet milling industry, as is the corn gluten meal, a protein supplement that contains a large amount of bypass protein, or UIP, commonly marketed to the dairy, poultry, or pet industries.The importance of understanding the process is that the resulting feed products from these two industries are quite different.

For more information or to request additional copies of this manual, contact the Nebraska Corn Board at 1-800-632-6761 or e-mail k.brunkhorst@necorn.state.ne.us.

Download PDF version of this manual, or



For more information on the feeding of corn milling co-products to beef cattle
and information contained in this manual, contact:
Dr. Galen Erickson, University of Nebraska-Lincoln, Department of Animal Science Room C220, Lincoln, NE 68583-0908, 402-472-6402

Date published: August, 2007