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Ethanol Production - Dry Fractionation

Fractionation is an additional step in the traditional ethanol dry-grind production process that is conducted to increase plant efficiency, lower greenhouse gas emissions, and produce co-products of higher value (e.g.enhanced distillers dried grains).

Dry fractionation involves removal of the germ, fiber, and endosperm from the corn kernel (Murthy, et al., 2006). Essentially, the corn kernel is separated into component parts. The germ portion of the corn kernel is high in corn oil, which is a potential feedstock for biodiesel. Removal of this oil and fiber in the kernel leaves a higher percentage of starch for ethanol production. This reduces the volume of material entering the plant which increases throughput and overall efficiency.

With less material entering the plant and a higher proportion of the kernel (starch) being converted to biofuel, fractionation reduces the volume of distillers dried grains (DDGS) produced. The lower quantity of DDGS produced do contain higher protein levels though (Martinez-Amezcua, et al., 2007). This benefits producers of non-ruminant animals by increasing digestability. Ethanol-production equipment manufacturer ICM calls these higher quality DDGS “Hi-Pro DDGS” because of the increased protein content per ton of dry matter.

Another benefit of dry fractionation is that it can greatly increase biofuel plant production efficiencies. DDGS production decreases under fractionation because other parts of the corn kernel are utilized more efficiently. However, higher quality (high-protein) DDGS can lead to increased value as hog and poultry feed which increases the value of the co-product to animal feed manufacturers. While use of DDGS for domestic animal feed and exports have both steadily increased, continue growth of the ethanol industry produces larger amounts of DDGS which poses a marketing challenge for the ethanol industry. Dry fractionation, which leads to lower volumes of DDGS produced, helps ethanol producers maintain stable DDGS prices.

Rajagopalan, et al. (2005) show that using degermed defibered corn (DDC) dry-fractionated corn increases return on investment by about two percent on a hypothetical 40 million gallon per year plant. The additional quantity of ethanol production, as well as higher protein DDGS, more than offset increased capital costs for the new technology. The addition of an oil expeller, which separates the oil from the corn kernel would enhance profitability of dry fractionation even further. 

While dry fractionation is not the only technology available for corn ethanol producers to increase efficiency or throughput, it fits a conventional dry-mill plant well, and can form a bridge to cellulosic ethanol (Deutscher, 2009).  Fewell and Gustafson find that while ethanol firm profits are uncertain and acquisition of new dry fractionation equipment poses considerable investment risk, increased profits from dry fractionation technology helps the firm increase long-run financial resiliency.


Fewell, J. and C. Gustafson. Do Lender Imposed Sweeps Affect Ethanol Technology Investment? Staff paper ???, Agribusiness and Applied Economics, North Dakota State University, Fargo, ??? 2010.

Martinez-Amezcua, C., C. M. Parsons, V. Singh, R. Srinivasan, and G. S. Murthy. 2007. Nutritional Characteristics of Corn Distillers Dried Grains with Solubles as Affected by the Amounts of Grains Versus Solubles and Different Processing Techniques.” Poultry Science. 86:2624-2630.

Murthy, G. S., V. Singh, D. B. Johnston, K. D. Rausch, and M. E. Tumbleson. 2006a. “Evaluation and Strategies to Improve Fermentation Characteristics of Modified Dry-Grind Corn Processes.” Cereal Chemistry, 83(3):435-459.

Rajagopalan, S., E. Ponnampalam, D. McCalla, and M. Stowers. 2005. “Enhancing Profitability Of Dry Mill Ethanol Plants.” Applied Biochemistry and Biotechnology, 120(1):37-50.


Cole Gustafson, North Dakota State University
Jason Fewell, Kansas State University

NDSU, Dept. 7620

P.O. Box 6050

Fargo, ND  58108-6050

Phone: 701.231.7261

Fax: 701.231.1008

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