Missoula’s poplar farm to become mulch, land will grow alfalfa

Martin Kidston

(Missoula Current) With no market and few buyers for wood products, the City of Missoula plans to remove the poplar trees at its wastewater treatment plant and replace them with a crop of alfalfa, which it can sell on the local market.

It also plans to use a portion of the property as a tree farm to support the city's efforts to get more trees into more neighborhoods, parks and landscaping.

“The poplar trees will be ground down and used as mulch so that carbon will be sequestered in the soils at the poplar farm,” said Chris Rowe, a member of the city's Energy and Climate Team. “We'll continue to work on carbon sequestration as well as the primary goal of water treatment and quality out there.”

The city created the poplar farm in the early 2000s to reduce its release of phosphorus and nitrogen into the Clark Fork River, beyond what the wastewater plant was capable of doing on its own.

During the growing season, the city diverts around 1.3 million gallons of treated wastewater daily to irrigate the tree farm. The plant activity absorbs the phosphorus and nitrogen into the plant tissue, creating cleaner runoff.

But while the process has worked well, the use once envisioned for the wood product is no longer viable. The roughly 90,000 trees will be removed this year.

“The thought was they could harvest these trees and send them to a mill where they'd be made into some sort of wood product,” Rowe said. “But the market for that fell out. We've been left with this question for years about what to do with the trees.”

The city still sees the property and its nutrient rich soil as a beneficial tool to keep the river clean while capturing carbon. As the trees are removed, they'll be ground down into mulch, which Rowe said will place the carbon back into the soil.

Contractors will do the work, he added.

“You're going to get two or three feet of organic material that you can put on the ground,” Rowe said. “That material will break down and most of the carbon that resides in the plant material will remain in the soil as organic matter.”

Rowe said the city also sees an opportunity to use the property to grow other products, including alfalfa and grasses, which can be sold as feed for livestock and generate revenue for the city.

Water from the treatment plant will be used to irrigate the crop. The city will also use the property as a tree nursery.

“They want to do this pretty fast. They want to be able to do it this coming year,” said Rowe. “They'll cut the poplar trees down and mulch them so they can capture the next growing season, and possibly the end of this one.”