While distiller's grains may work in plastics industry, USDA has no plans to divert them from feed troughs

BROOKINGS, S.D. -- While the corn ethanol industry looks at ways to extract more value from processing co-products such as dried distiller's grains, U.S. Department of Agriculture researcher Kurt Rosentrater assures livestock producers that his s...

BROOKINGS, S.D. -- While the corn ethanol industry looks at ways to extract more value from processing co-products such as dried distiller's grains, U.S. Department of Agriculture researcher Kurt Rosentrater assures livestock producers that his studies on using DDGs in plastics are not intended to divert feed from the livestock industry.

He has been testing the use of DDGS, dried distiller's grains with solubles, and DDGs in plastics at USDA's Agricultural Research Service North Central Agricultural Research Laboratory in Brookings, S.D., since 2004. He conducted his research with professor Robert A. Tatara and Andrew W. Otieno of Northern Illinois University department of technology. Their findings were published recently in the Journal of Polymers and the Environment, a plastics industry trade journal.

10 million-ton question

"The thing that was on everyone's mind back then was the 10 million-ton question: What are we going to do with all this distiller's grain?" he says. "This was back when it was 5 (million) or 6 million tons a year production. And now it's 16 (million), 17 (million), 18 million tons, so people are asking me, 'Why are you taking this valuable feed and putting it in plastic?'"

Rosentrater says he's not. He wants to take the remains after the feed components are extracted and use that for bio-plastics.


"We've only taken a couple steps down that path right now, but that's ultimately where I'd like to see this go," he says. "So can you provide the animals their livestock feed and biodiesel, if you pulled the oil out, and other things, and then what can you do with what's left?"

DDG production this year reached 17 million tons, the vast majority of which went to animal feeds in the cattle, swine and poultry industries. Because of this, Rosentrater does not see a need right now to find new things to do with DDGs.

"But five years from now, 10 years from now, when we have the large-scale bio-refineries working on corn, ligno-cellulosic materials and other biofuels, there will be a need potentially at some point to say, 'What can we do with this if it has no animal feed value?'" he says.

Hard science

The goals of his research are twofold.

"What we're really trying to do, No. 1, is prove the concept: Can you use DDG or corn fibers?" Rosentrater says.

Plastics have been made with petroleum-based products since their invention. With the rising costs of oil, though, a lot of research has gone into the use of filler products, which are intended to replace some of the petro-chemical volume of the plastic without sacrificing strength. Other fillers that are being evaluated include bamboo, corn stover and soybean hulls.

One selling point for DDGs, he says, is the fact that distiller's grain, while it's increasing in cost, is still fairly low compared with some of the petroleum-based fillers.


"I saw it today at about $200 a ton, so I think it would be of some economic benefit to doing it today," he says.

Rosentrater's laboratory has produced compression-molded samples made of 50 percent phenolic and 50 percent DDGs that resemble oversized dominos. They are rigid, smooth and dense. He also has tested plastics with varying amounts of DDGs.

There is a trade-off though. Increasing the biologic content, whether it's distiller's grains or something else, typically leads to a decrease in the plastic's strength.

"We've gone up to 90 percent (DDG content), but the resulting plastic did not have very good structural properties," he says. "What we're seeing is 50 percent is a pretty good level. We're retaining good strength values and we have relatively good biodegradability."

The lab runs a series of strength tests on each sample to see how much strength it takes to bend it, pull it apart or even smash it together. The 50-50 mix is still the best.

"We can do this today," Rosentrater says, adding that a company in Illinois is making road signs from DDG plastics. "There hasn't been a lot that's been published, but I think the interest is there."

Breaking it down

His No. 2 goal is providing a plastic product that will degrade or break down after the product is discarded and it winds up in the landfill. Phenolic resins are not environmentally friendly.


"If you were to put 100 percent phenolic-based plastic buried in a landfill it wouldn't degrade over time," he says. "It does have degradability, but it's years and years. (With) 50 percent distiller's grain, you can get 30 (percent) to 40 percent degradability within 12 weeks."

Beyond that, Rosentrater hopes to see the research go a step further.

"What if you use, instead of phenolic . . . if you used something that's bio-based, like polylactic acid, that's totally bio-based?" he asks. "Then you would have a completely biodegradable product, and if you can use DDGs as a reinforcement fiber, then you could get some benefit from that."

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