Ethanol waste, or still grains, is a co-product of the dry milling process used to produce ethanol from corn. It is sold as a feed supplement for livestock, containing nutrients three times higher than the original corn input. It is particularly valuable as a high protein and energy supplement for cattle, poultry, and pigs.
Ethanol, or grain alcohol, is a high-octane, renewable biofuel that is commonly produced from corn, sugar cane, and other sugar crops. Waste ethanol is an important co-product of the ethanol manufacturing industry. Also referred to as still grains, it is essentially the sludge left over from the ethanol production process. Initially discarded as industrial waste, a number of commercial uses have since been developed for this waste by the evolving industry.
Two primary manufacturing processes are used in the production of ethanol from corn: dry milling and wet milling. A primary difference between the two processes is the co-products that each generates. Ethanol waste is a co-product of the dry mill manufacturing 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, corn starch is converted into ethanol. This ethanol is distilled into alcohol, leaving the distillers grains behind.
Once the ethanol has been extracted, the waste is usually dried and sold, often as feed or feed supplement for livestock. It is sold in various guises, including dry grain distillers with solubles (DDGS), dry grain distillers (DDS), and dry grain distillers (DDG). DDGS is the most common form marketed to the feed industry. From each 56-pound (25.4 kg) bushel of corn, 2.7 gallons (10.2 liters) of ethanol and approximately 17 pounds (7.7 kg) of waste are produced. For every 1,000 bushels (25.4 tons) of corn used in ethanol production, approximately 8 tons (7.2 tons) of DDGS are produced.
Ethanol waste is a highly nutritious feed for cattle, poultry and pigs. Thanks to the dry mill manufacturing process, it contains nutrients in concentrations three times higher than the original corn input. That’s because the process consumes only the starch content of the corn, which makes up over two-thirds of the grain. All remaining nutrients are concentrated in the waste, creating a valuable livestock feed product.
The resulting product is particularly valuable as a high protein and energy supplement. Calves and lactating cows, for example, may need protein and energy supplements, and wheat meets both of these requirements. Plus, because it contains very little starch, it has the added benefit of not hindering fiber digestion.
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