The world can’t get enough cardboard.

Even though it is reused more than almost any other product, there is a global shortage of what industry calls OCC, old corrugated containers, which paper mills recycle into new containers. The demand is spurring cost increases that have paper mills looking at fiber alternatives — like corn stalks, kenaf, straw, even hemp.

Why a shortage? The global trade imbalance may be to blame.

Countries such as China export vastly more products to the United States than they import. “They have all these empty containers going back that they can fill with recycled papers,” says Larry Newell, manager of Liberty Paper, a Becker, Minn. mill that recycles cardboard into new containers.

The Chinese use the OCC to make cardboard “to put all the stuff we’re buying into containers to ship back here,” says Michael Sparby, AURI project director. “So the price for recycled cardboard keeps going up.” In countries such as China where wood pulp is in short supply, recycled papers are more economical to make than virgin.

To find alternatives to OCC as well as wood pulp, AURI is revisiting a decade-old study that looked at using straw pulp instead of wood to make fine papers. When the original six-year study was completed in 2000, pilot plant trials showed straw paper was “technically feasible but the economics were way out of whack,” Sparby says. The return on investment, “to build a $700 million (straw) pulping facility for fine paper was a negative 5 percent. There wouldn’t be many companies jumping at that one.”

But with pulp costs rising, alternative paper fibers are getting another look by a consortium from the University of Minnesota, state Department of Energy and Economic Development, Legislative Commission on Minnesota Resources and AURI, representing Minnesota wheat growers.

“Through this consortium, we were put in touch with Liberty Paper … they are working with technology to blend wheat straw with recycled cardboard to make new cardboard,” Sparby says.

Liberty Paper in Becker, Minn. makes corrugated cartons, tubes and specialty bag papers from recycled corrugated containers. “We make about 165,000 tons of finished product a year … keeping 200,000 tons of OCC out of the landfills,” annually, Newell says.

Liberty Paper is one of a dozen divisions of Liberty Diversified Industries of New Hope, Minn., a major manufacturer. The paper division is one of only two mills in Minnesota that recycles corrugated containers. “We don’t chop trees down to make wood pulp — that’s a whole different process. We’re 100-percent recycled.”

But recycled paper “is a commodity as well and very volatile in the marketplace,” Newell says. “We want to find some alternative material that can be made into paper substrate that has some stability to it. Both the inside and outside of a corrugated box is designed for strength, not appearance like fine papers.”

Of all the alternative fibers Liberty Paper has looked at, “wheat is the best suited because of its fiber characteristics … and there is an abundance of it in Minnesota.” The straw-OCC blend would likely be used in the cardboard’s wavy interior where it needs to be durable and the straw flecks won’t affect appearance.

The cost of the wheat straw, baling and transportation would still be less than the price of recycled cardboard, Sparby says. But other hurdles have to be overcome, such as storing straw year-round and the economics of launching a new process. Because breaking down straw fibers is different than using OCC, new equipment has to be installed.

AURI, with the University of Minnesota, is preparing to analyze all of Minnesota’s wheat varieties for fiber length, durability and other paper-making attributes.

If wheat-straw paper making is feasible, “theoretically, a new $80 million plant in northwest Minnesota would use a hundred thousand tons of straw a year, mixed half with recycled cardboard,” Sparby says.

“It could be a direct $3 million value-added to the wheat growers.”