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The steps in producing ethanol, very basically, are that the corn is ground, digested and then fermented (see the figure below). First the corn is ground to

increase the surface area so the microbes and enzymes can more efficiently access the nutrients (mostly starch). Then the starch is digested to convert it into sugars that can be metabolized by the fermentation microbes. The major products of the fermentation step are CO2 and ethanol. The ethanol is distilled from the fermented liquids and the remaining liquid mash is separated by centrifugation into distillers’ grains and wet condensed solubles. Both are dried and reconstituted to make DDGS. The primary product of interest in the process is ethanol. The other products (DDGS and CO2) are generally referred to either as by-products or co-products. As the values of these products are considerably lower than ethanol they should accurately be referred to as by-products.

As an important note, there is some movement by some ethanol producers in North America to remove the oil from the wet condensed solubles before drying and reconstituting it into DDGS. This would lower the energy worth of the DDGS which would dramatically alter its nutrient content and value for livestock. For example, it would lower its nutrient value for swine. It is not immediately clear what impact it would have on mature ruminants as removing the oil could also lead to

higher possible inclusion rates. This is because too much oil in a ration decreases the ruminal microbes’ ability to digest fibre. What that balance will be (lower energy (bad) vs. lower fat density (good?)) for lambs is not clear. If and when that process is adopted in Ontario it is important for shepherds to be aware of source and process as both products will be properly called DDGS.

Figure showing the basic process by which DDGS is produced. OSN

The Process of Making Dried Distillers’ Grains with Solubles (DDGS)