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Turning tailings

East Grand Forks, Minn. — Like overstuffed sausages, huge plastic tubes filled with silage rest outside the American Crystal Sugar processing plant. The 250-foot tubes hold some 400 tons of silage apiece — and a promise for adding value to sugar beet processing.

Annually more than two million tons of beets are processed here into the familiar granulated sugar sold with the round Crystal Sugar logo. But as with nearly all ag processing, the process yields coproducts such as pulp and tailings. Much of the pulp is pelleted and sold as livestock feed. But the tailings, mostly beet tips, beet parts and a few leaves, must also be dealt with.

Process engineer Sheldon Seaborn says the East Grand Forks plant produces about 80,000 tons of tailings per year. Some are fed to cattle; ranchers have come from as far away as Dickinson, N.D., a distance of nearly 400 miles, just to pick up a load of tailings. When cattle are pastured during warmer months, however, or the weather is too cold to haul wet tailings, it is difficult to give them away. Significant amounts have to be land-applied to area farm fields at a net cost to the cooperative.

“We spent $400,000 last year to land-apply tailings and pulp,” Seaborn says.

To find a way to cut those costs, American Crystal Sugar began working in late 2001 with Alan Doering of the AURI coproducts utilization lab in Waseca.

Doering constructed a number of “mini silos” to allow the tailings to ferment and be used as silage. He mixed tailings with several other agricultural products to find a blend that was cost effective, yet reduced the moisture level to the point where fermentation could occur.

“Moisture is the critical element here because the tailings are so wet,” Doering says. “We mixed them with different products to find the right blend.”

In January, American Crystal Sugar filled eight 12-foot diameter bags with more than 3,000 tons of various blends of tailings and pulp. The sealed bags allow the fermentation process to preserve nutrients and extend the time that silage is available to producers.

Seaborn says the ability to market a consistent product over a long time could help the bottom line. Now the challenge is determining the silage’s marketability and setting a fair price.

“The goal is to cut costs to zero,” Seaborn says. “At this point we’re not worried about making money on the tailings. The opportunity is to take advantage of the fall and winter months when it’s difficult to move the raw tailings. Ensiling (fermenting in silos) will make tailings available as feed for a longer time.”

“This is an excellent example of a business taking a material that costs them money for disposal and converting it into something that has value,” Doering says.