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Definitions of the Ethanol Industry - a Nutrient and Livestock Perspective

Nutrient Management Notes
October 11, 2006

The Ethanol industry is gaining momentum and from questions I get there is a lot of confusion on some of the terms within this industry. Producers continue to talk about gluten feeds when chances are they are feeding distillers products. There is a difference. The phosphorus and sulfur contents vary dramatically.

Wet Milling process

Yellow shelled corn that is cleaned and steeped (softened) in tanks with a water-based solution, releasing starch. The steepwater is then drawn off and corn is milled, breaking the germ loose.  Mechanical and solvent processes during germ separation extract oil. The corn leaves the germ separator in the water suspension for further grinding to release starch and gluten from the kernel fiber. 

The Wet Milling Process produces four major co-products for the feed Industry:

  • Condensed corn fermented extractives
  • Corn germ meal
  • Corn gluten feed  1% Phosphorus, 0.3% Sulfur
  • Corn gluten meal  0.48% Phosphorus, 0.65% Sulfur

Dry milling

Yellow shelled corn is cleaned and then ground into "meal". The meal is then slurried with water to form a mash, enzymes are added to the mash to convert the starch to dextrose. Yeast is added.  The fermentation process converts the sugars to ethanol and other by-products.

Averaged results. Each processing plant is slightly different!!

  Phosphorus Sulfur
Corn distillers dried grains (DDG) 0.37% 0.43%
Corn distillers grains/solubles (DDGS) 0.71% 0.33%
Corn condensed distillers solubles (CDS) 1.3% 0.3%
Wet distillers grains (WDG)    
Modified wet distillers grains/solubles (MWDGS)    

All of the co-products above are feed to livestock in some degree. Each of these products has their pros and cons, such as the phosphorus and sulfur content. In a conventional corn, corn silage ration for cattle the National Research Council's (NRC) guidelines are meet for phosphorus of 0.35%. When ethanol co-products are included in the cattle feed ration the phosphorus that goes in and the portion that is not retained by the animal must come out resulting in higher phosphorus content of the manure's. The only way to truly know what is in the manure is to sample.

The Iowa Beef Center at Iowa State has developed a spreadsheet that can be used to estimate the amount of phosphorus that will be excreted from a feedlot. This spreadsheet compares and existing ration that is of conventional feedstuffs and allows the user to choose the amount of ethanol co-products that that they are thinking of using. The spreadsheet also allows for input of producer analysis of the co-product or to choose from a list of ethanol plants. One thing you will notice is that, even though the process may be similar, all of the plants have different analysis of their co-products. This reemphasizes the need for manure analysis if producers are least cost shopping for their ethanol co-product to be used in their cattle ration.