Ethanol Co-Products: A Growing Feed Resource
The current expansion and potential for continued growth of the ethanol industry is increasing the availability of alternative feed resources – ethanol by-products. These by-products, often termed co-products, can be used as a supplemental feed source for beef cattle as part of backgrounding and finishing diets, in forage-based diets, and in creep feeds.
According to the Renewable Fuels Association, the United States has 107 ethanol refineries in
production, 49 under construction, and more on the drawing board. Corn is the favored raw material for
the lion’s share of both current and future facilities. Thus, the making and marketing of feed ingredients
is becoming an increasingly important aspect of the ethanol business.
Wet vs. dry milling
As feedstuffs, distillers grains and other coproducts are not new. Yet many cattle producers lack clear understanding of the various products and how they differ. Livestock nutritionist Dr. Matthew Gibson, vice president of technical services and marketing for Dakota Gold Marketing, explains different ethanol production processes yield different co-products. It depends on whether a wet milling or dry-grind (dry milling) process is used.
Dakota Gold Marketing is an arm of Broin Companies. Broin-operated plants yield about 22 percent of the dried distillers grains fed in this country, and Dakota Gold ranks first among distributors of dried distillers grains.
Gibson explains that wet milling involves soaking or steeping whole corn to soften the kernels. The,
further processing separates components. Processors are mainly after the starch fraction used in products such as dried corn starch, corn syrup, and sweetener. Another valuable fraction is the corn oil. Many of these products are marketed for human consumption. Some starch may also be converted to dextrose and fermented to create ethanol. The principal wet milling co-product used as cattle feed is called corn gluten feed.
Generally, fuel ethanol production is the primary goal of companies, like Broin, that use dry-grin
processing. The grain is ground and fermented to convert the starch into alcohol (ethanol). Distillation
to remove the alcohol leaves wet distillers grains and distillers solubles. These products may be marketed separately, or distillers solubles can be added back to the wet grains. Typically, blended distillers grains with solubles is sold as a dried feed ingredient, such as Broin’s Dakota Gold product.
“Distillers grains are a tremendous feed ingredient for feedlot rations, with five to 15 percent more energy than corn. Some studies have shown the difference to be even greater,” states Gibson. “With the starch removed, distillers grains are safer than corn – less risk of acidosis. And because they are a good source of protein, they also can replace part of the ration’s protein supplement.”
Corn is roughly two-thirds starch, with that removed during ethanol production. So the nutrients contained in distillers grains are concentrated three-fold, compared to corn. Providing considerable energy, protein, and minerals, distillers grains contain 27 to 30 percent crude protein, 11 to 12 percent fat, and 0.8 to 0.9 percent phosphorus (all on a dry matter basis).
The advantage of dried distillers grains, explains Gibson, is its stability and ease of storage. The wet
product has a relatively short “shelf life” and will spoil unless stored in a pit or in big silage/haylage bags to reduce mold growth. Unless properly stored, producers won’t want to have more on hand than
can be fed up in a few days. Another consideration is cost. Wet distillers grains often appear to be less expensive, but usually contain 65 to 75 percent water.
Distillers grains vs. corn gluten feed
Perhaps least understood by many livestock producers are the differences between distillers grains and corn gluten feed. The latter, as mentioned previously, results from the wet milling process. It too is
sold in wet (40 to 60 percent dry matter) and dried (85 to 90 percent dry matter) forms. Wet corn gluten
feed’s energy content is similar to slightly higher than that of corn grain, while dried corn gluten feed’s
energy content is lower than corn’s.
Wet corn gluten feed also poses the same storage and transportation cost challenges as wet distillers grains. Compared to distillers grains, corn gluten feed has slightly lower levels of crude protein and fat,
and slightly higher phosphorus content. Another difference related to protein is that 80 percent of corn gluten feed’s protein is rumen degradable, compared to 35 percent for distillers grains.
Rumen-degradable protein must be converted to microbial protein in order to be utilized by cattle.
Like the feedlot industry, other sectors can benefit from ethanol co-product feeds. Dried distillers grains and dried corn gluten feed can fit well in calf backgrounding rations and beef cow diets utilizing low-quality forages. The co-product feeds supply energy, without the starch that can inhibit digestion of forages. They provide protein beneficial to rumen microbes, enhancing the bugs’ ability to break down fiber.Supplementing grazing cattle with co-product feeds may also meet the animals’ requirements for phosphorus, thus eliminating the need for additional supplemental phosphorus in freechoice mineral mixes.
Co-product limitations
Ethanol co-products do have some limitations. For some producers, bulk product isn’t very convenient.
Some companies are improving the integrity of their pellets or range cubes, but many producers have
been disappointed with soft, crumbly products in the past. University of Nebraska Extension Feedlot Specialist Galen Erickson says some of the products’ advantages can become liabilities. For example, the high phosphorus levels that might be an asset to grazing animals can challenge feedlot manure
management.
“Frankly, corn (grain) provides more phosphorus than the animals need. Using (co-products) adds more, bumping levels from about 0.3 percent to around 0.5 percent in the diet,” explains Erickson. “A
greater excess in the diet means more phosphorus is excreted in manure, and close to double the cropland acres are needed to distribute the manure as fertilizer.”
That might be a problem in some localized areas, but it’s not as bad as it might sound. Erickson says high-phosphorus manure can be valuable. It should be to farmers that apply phosphorus as part of
an expensive commercial fertilizer program.
Another limitation of distillers grains is related to the product’s high fat content. Too much fat in the diet can hinder rumen fermentation and reduce fiber digestion. Erickson recommends that total fat content not exceed seven percent of forage-based diets, or eight percent of finishing rations, on a dry matter basis.
Distillers grains and corn gluten feed are relatively high in sulfur and too much dietary sulfur may contribute to development of a neurological disease called polioencephalomalacia. Generally, it is recommended that sulfur comprise no more than 0.4 percent of the diet dry matter. If sulfur is a problem, Erickson suggests feeding 100 to 150 milligrams daily of thiamine (a B-vitamin). And test
the water. Special care must be taken in areas where the sulfur content of water is high.While no rule-of-thumb is fool-proof, Erickson says most dietary problems can be avoided if ethanol co-product feedstuff inclusion rates do not exceed 40 percent of the ration on a dry matter basis.
One other reason to watch inclusion rates is the effect ethanol co-products may have on carcass merit. After conducting a review of 13 university studies, Kansas State University Extension Feedlot Specialist Chris Reinhardt notes that evidence suggests co-product inclusion rates above 30 percent may result in
reduced marbling (intramuscular fat) deposition and lower quality grade. While this point is controversial, researchers speculate that low levels of starch in the diet may be the cause of small but
statistically significant differences.
Many scientists and cattle feeders dismiss the notion of reduced quality grade due to co-products
feeding; Erickson considers it a non-issue, as long as co-product feed ingredients are not fed at exceedingly high inclusion rates. Co-products: good for the industry There is little argument over
whether co-product feedstuffs will play an increasing significant role in cattle diets. As a whole, ethanol
co-products are considered good for the beef cattle industry.
“They work really well. And particularly in areas near the plants, they have made cattle feeders very
competitive. I’m really optimistic about the future,” offers Erickson. “Most of the ethanol industry
expansion will involve dry milling, so we can expect more production of distillers grains. We’ll see more
corn gluten feed too, and I look for increased availability of more and different kinds of co-products,”
Erickson adds.
“But producers will have to remember that not all coproducts will be equal. They will need to know just what they are buying and how to use it.” Dr. Matthew Gibson and Dr. Galen Erickson discussed ethanol production and corn byproducts and feeding ethanol byproducts to cattle at the December 2006 Academy of Veterinary Consultants Meeting in Denver, Colo.
Starch to Ethanol
Ethanol, a renewable energy source, can be produced from a variety of substances. The predominant substance is corn (and other grains), but ethanol can also be produced from wood waste, cheese whey, waste sucrose, potato waste, brewery waste, and food and beverage waste. At its most basic, the process involves exposing the starch in the substance and then undertaking a fermentation process. When this process is used with corn, it may be done in one of two ways: dry milling (or dry-grind processing), the most common type of ethanol production in the U.S., or wet milling.
Corn contains approximately 61 percent starch, thus it’s easy to see why this grain is an ideal substance for ethanol processing. One bushel of corn produces 2.7 gallons of ethanol, 18 pounds of ethanol co-products, and 18 pounds of carbon dioxide. Co-products – by-products – of ethanol production that can result from dry milling, and are of interest to the beef industry, are:
- dry distillers grains
- dry distillers grainswith solubles
- wet distillers grains
- wet distillers grains with solubles
- condensed distillers solubles