Extract or Enrich

FROM THE DECEMBER ISSUE: Corn oil maximization seems an obvious goal, but some DDGS feed markets prefer a higher oil content for better energy value.
By Susanne Retka Schill | November 17, 2017

With corn distillers oil (CDO) selling for around 25 cents per pound and DDGS for a nickel per pound, extracting as much CDO as possible is the goal for many plants. CDO sales account for an important, albeit small, revenue stream, particularly when margins are thin.

The ethanol industry’s corn oil heads to two markets: feed and biodiesel. According to the U.S. Energy Information Administration, biodiesel producers used 1.3 billion pounds of CDO in 2016, about 12 percent of the total feedstock requirement. Biodiesel consumed 842 million pounds of CDO through July this year, ahead of last year’s pace—673 million pounds.

USDA’s Grain Crushings and Co-Products Report says just over 1 million tons of CDO were produced through July this year, compared with 893,000 tons through July last year. Biodiesel has used about 42 percent of CDO production so far this year.

The remaining 60 percent of CDO heads to the feed market, where it is used for energy. Mark Newcomb, senior nutritionist for Iowa-based NutriQuest, explains some diets requiring higher energy levels will add corn oil or other sources of fat. “Think about a young pig diet, for example, sometimes you need extra energy.” On the feed market, CDO competes with other sources of fat used for energy, such as yellow grease (recycled restaurant oils), white grease and tallow. Some feed programs restrict the use of animal fats, opening the market for a vegetable-based oil, such as CDO.

DDGS Impact
Extracting corn oil and selling it separately reduces the oil content in DDGS, of course. “As I think of DDGS, I don’t categorize high or low oil as good or bad,” Newcomb says. “I think of it as nutrient value and how it competes with other options that are available. I may not love the variability between sources of DDGS, but assuming I can manage that in my formulation correctly, it is what it is.”

Newcomb reports oil levels vary between 5 and 7 percent in DDGS in the samples NutriQuest analyzes, with a few coming in as low as 3 percent. The greatest variations come with the new crop. “This time of year, nutritionists like myself worry about the variation we’ll see over the next few months.” Just as toxins get concentrated in DDGS by a factor of three, any changes from crop to crop in protein or other key nutrients are amplified.

Clearly, the feed industry is adapting to low-oil DDGS, Newcomb says, “Particularly those of us who have a system to monitor and monetize the variation correctly, so you can discriminate appropriately among the varying oil and nutrient levels that DDGS provide. It’s a matter of having your system synced with your supply of DDGS.” Unannounced changes can be a problem, he adds. “We can handle it either way, but subtle process changes where you’re pulling more oil out or adding more or less of the solubles back add to inconsistency that can be tough to track from a user perspective.”

NutriQuest’s Illuminate service tests DDGS samples sent in by customers and charts the variability in nutrients over time at individual plants. Newcomb estimates about 60 percent of the ethanol industry is represented in its databases.

Energy Value
Low-oil DDGS, under 5 percent, might be an advantage in certain rations, such as for late finisher pigs, Newcomb says. High corn oil levels can cause soft fat to be laid down as the pig puts on finishing weight, resulting in soft pork bellies—an undesirable trait for bacon lovers. While low fat might be desirable for that one feed ration, far more often high fat content contributes a major component of energy levels in feed rations. Thus, reduced oil can limit DDGS use. 

When low-oil DDGS first arrived on the scene, the loss in energy value prompted concern. “We’ve been fighting this battle since the start,” says Jennifer Aurandt, director of technical services at Valicor. “We’ve worked with nutritionists, and while oil content contributes energy,  it’s not the driver of metabolizable energy. A lot of it has to do with the processing of DDGS.” She cites research done at the University of Minnesota, Auburn University and the USDA Agricultural Research Service that has found a poor relationship between crude fat and metabolizable energy in DDGS sources. The researchers recommend using a formula including crude fat, protein and fiber to calculate the metabolizable energy value more accurately than using the crude fat number alone.

Newcomb explains that DDGS under 5 percent present another challenge. “When you get into really low oil distillers products, there is a concern about whether the residual oil is digestible and a true energetic fat,” he says. Crude fat measurements include oil soluble compounds that don’t provide energy, such as vitamins. Normally a small percentage, as more corn oil is extracted, the proportion of those fat solubles goes up, throwing off energy calculations. Crude fat levels higher than 5 percent have a “pretty good correlation between fat content and energy,” he adds.

With many feed specs calling for 7 percent oil content and export specs calling for 34 pro-fat (the sum of protein and fat content), it’s important that plants shipping DDGS to distant markets take out the right amount. Ethanol producers can adjust the amount of oil removed, Aurandt says, by dialing down their chemistries—the demulsifiers used to improve extraction rates. Another approach is to turn off the chemistry on one centrifuge, mixing the full-fat stream with the low fat from the other centrifuges.
Reduced-oil DDGS might only be the first of many adjustments to DDGS value, Aurandt says. “We really see a shift coming on what DDGS are, if you look at the innovators extracting protein or doing cellulosic from corn fiber.” Though only a handful of plants are implementing those innovations at this point, fermentation aids like proteases or cellulases are impacting DDGS now, not to mention enzymes designed for DDGS enhancement. Changes in the front end to help fermentation affect how the solids behave and require changes down the line, she points out, including adjustments to corn oil extraction. Many of the new processes promise increased oil extraction as a benefit, but that might not necessarily mean issues for feeders, Aurandt says. “As the industry extracts more oil with these changes, we may increase the digestibility of other components within the stillage matrix, therefore increasing the energy content of the DDGS.

“Just as in the beginning of the corn oil extraction era there was a concern about lower-oil DDGS and finding a market for them, we are entering into an era that is now redefining the dry-grind ethanol process to extract more value from the coproducts, therefore changing the identity of DDGS,” Aurandt says.

Author: Susanne Retka Schill
Freelance Journalist