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Ethanol, or grain alcohol, is a high-octane, renewable biofuel that is commonly produced from corn, sugar cane, and other sugar-bearing crops. Ethanol waste is an important co-product of the ethanol manufacturing industry. Also referred to as "distillers grains," it is essentially the mush that is leftover from the ethanol production process. Initially discarded as industrial waste, a number of commercial uses for this waste have since been developed by the evolving industry.
Two primary production processes are used in the manufacture of ethanol from corn: dry mill and wet mill. A primary difference between the two processes is the co-products that each generates. Ethanol waste is a co-product of the dry mill production process, while gluten feed is a co-product of the wet mill process.
Dry mill ethanol production is a relatively simple process. It basically involves the grinding, fermentation, and distillation of field corn. During the fermentation process, the starch in the corn is converted into ethanol. This ethanol is distilled into alcohol, leaving behind distillers grains.
Once the ethanol has been extracted, the waste is usually dried and sold, often as a livestock feed product or dietary supplement for cattle. It is sold in various forms, including distillers dried grains with solubles (DDGS), distillers dried solubles (DDS), and distillers dried grains (DDG). DDGS is the most common form that is marketed to the animal feed industry. From each 56 pound (25.4 kg) bushel of corn, 2.7 gallons (10.2 liters) of ethanol and roughly 17 pounds (7.7 kg) of waste are produced. For every 1,000 bushels (25.4 metric tons) of corn used in the production of ethanol, about 8 tons (7.2 metric tons) of DDGS is produced.
Ethanol waste is a highly nutritious feed for cattle, poultry, and swine. Thanks to the dry mill production process, it contains nutrients in concentrations three times higher than the original corn input. This is because the process only consumes the starch content of the corn, which makes up over two-thirds of the kernel. All the remaining nutrients are concentrated into the waste, creating a valuable livestock feed product.
The resulting product is particularly valuable as a high-protein, high-energy supplement. Calves and lactating cows, for example, may need protein and energy supplementation, and the grain fulfills both these requirements. Furthermore, since it contains very little starch, it offers the added benefit of not hindering fiber digestion.