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Easing the sidestream flow

Waseca, MN — Ethanol is a triumph for Minnesota agriculture. The state’s annual production — 500 million gallons last year — was only 11 million gallons 15 years ago. And it’s likely to surge again in 2013 when a state provision could require a 20-percent ethanol blend in all gasoline sold here.

But in the wake of ethanol’s free-flowing fuel production, there are sidestreams that need to keep pace with the industry.Distiller’s grain, an ethanol coproduct, is typically coated with another coproduct: syrup. Then it is dried to yield DDGS or distiller’s dried grains with solubles. The Minnesota Corn Growers Association estimates the state already produces 1.4 million tons of DDGS per year, and more plants are being built.

Most of these DDGS are sold for poultry, swine and cattle feed, but supply exceeds the state’s demand, so the overflow is often shipped to global markets. However, long distances and moisture can cause the DDGS to become compacted and sticky, making it difficult to unload.

Alan Doering of AURI’s coproduct utilization lab in Waseca says some DDGS shipments have been discounted by thousands of dollars because of poor flow and the cost of extra labor and time to unload ships, train cars and trucks.

So AURI and the Minnesota Corn Growers initiated a study to see what conditions hamper DDGS flow and what may be done to improve it.

Many of the corn association members and leaders “are also investors in these ethanol plants” and aware of the flowability problems, says Yvonne Simon, a Minnesota Corn Growers staff person.

About 5,000 producers own shares in Minnesota’s 14 ethanol plants, which use 16 percent of the state’s corn crop, according to the Minnesota Department of Agriculture. Moreover, the industry leverages 5,000-plus jobs and $1.3 billion in economic activity.

“This is an issue that affects every ethanol plant in Minnesota,” Doering says. “It can impact their profitability, which means it affects the bottom line of the producers who have invested in them.”

The MCGA and AURI enlisted Jenike & Johanson, a bulk solids design and engineering firm from Massachusetts, to to evaluate various DDGS traits. The firm analyzed distiller’s grains flow characteristics, compared different grain hopper designs and outlet sizes, and tested the effect of pelleting grains.

Five DDGS samples were tested: two controls and three modified samples, including deoiled DDGS, a reduced-syrup sample and pelletized DDGS.

The study, completed in October, revealed that “particle size and relative humidity played the biggest roles in flowability,” Doering says. “We expected that the de-oiled DDGS and the pelleted distiller’s would flow best, but that wasn’t always the case.”

The study showed that larger particles flowed best, regardless of oil or syrup content. The larger particles even flowed better than the pelleted sample, which showed minimal improvement.

Humidity had little impact until it rose above 60 percent — at that point distiller’s grains quickly absorb moisture, which can reduce flowability. Particles also tend to expand as they warm, which can reduce flowability.

The study was the first of its kind in the country and has drawn attention from around the nation. “We don’t have all the answers yet, but what we do know about distiller’s grains now can impact not only ethanol plants but feed managers and even our own product development,” Doering says. “We’ve answered a lot of questions, but created a few more, too.”

“We have some information that is leading edge,” says Simon. “Now that we know how DDGS are affected by things like heat and humidity, we need to figure out how we can keep the distiller’s stable, so once it reaches markets like China, Japan or Spain, it flows and has good nutrition value.” ¦