Shakopee biomass firm takes Minneapolis tree waste

Five years after a unique biomass energy facility opened in Shakopee, it has quietly developed a productive marriage with the city of Minneapolis, which is eager to find a way to rid itself of trees.

"Koda Energy has become tremendously important to us in absorbing vast quantities of plant material without our having to pay anyone to take it away," said Ralph Sievert, Minneapolis' city forester. Koda burns the plant material to generate energy.

How vast are the quantities? Consider this:

A June windstorm that felled about 3,000 trees in Minneapolis generated about 71,000 cubic yards of wood and debris.

That much volume can be visualized as a bumper-to-bumper lineup of VW Beetles stretching along the freeway from downtown Minneapolis to Burnsville Center.

And that's small potatoes compared to what the city is planning next, starting this year: A gradual clearout of 40,000 ash trees, aimed at getting ahead of the killer emerald ash borer without leaving boulevards denuded the way Dutch Elm disease did decades ago.

Koda, which generates heat and electricity for one of its owners, Rahr Malting, as well as for the electrical grid in general, winds up on the receiving end after a pair of stops for dumping and processing.

After that accident, which didn't injure anyone, Stacy Cook, vice president and general manager, sat down with a pen to sketch out what proved to be a $7 million reinvention of the facility to make it safer.

The owners were willing to make that investment even though the fracking natural gas revolution has severely undermined the economics of biomass energy.

"When the plant was proposed," Cook said, "natural gas had spiked to $13 per million BTU. At the low end, two years ago, that was down to $1.67.

"These days it's quite high again, as more industries move to take advantage; pricing has stabilized, and bounces up and bounces down.

"But no question, that makes it more challenging for us."

The plant takes in about 500 tons of material a day, or a semitrailer truck every hour, day and night.

"Over most of our existence we had been getting about 30 percent of our fuel from Rahr itself," he said, with another major contributor being breakfast cereal waste material from General Mills.

Lately, he said, Rahr's contribution has dropped closer to 20 percent as Koda has been burning up the debris from last summer's Minneapolis storm.

"They brought us 2,500 semi loads in first two weeks alone, and the volume didn't drop off much from that all summer long," he said.

It all goes first to a tipping site at Fort Snelling, then to a processing center in Scott County, once it has first been ground to a point where the ash borer cannot survive — lest the process wind up spreading the devastating problem to Scott County's suburbs.

"Our residents used to expect they'd get some free wood chips, but now there's a very good use for it," Sievert said.