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Forest thinning in Arizona produces mostly useless wood. New tech is trying to change that

By Michel Marizco
Published: Wednesday, May 10, 2023 - 4:05am
Updated: Wednesday, May 10, 2023 - 9:10am

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Michel Marizco/KJZZ
The CharBoss is effective at reducing slash piles to useful carbon.

Coconino County has aggressively been thinning its forests to try to reduce the amount of overgrowth that leads to violent fires like those last year that burned more than 30 homes and 80 square miles. But current thinning practices don’t create desirable logs with any real use. So it’s trying out different technologies to eliminate a growing problem ahead of any new fires. 

The landscape changed in northeast Flagstaff after the fires last year. The Tunnel Fire destroyed homes and then weeks later, the Pipeline Fire decimated the area’s natural buildup against flooding. Then those floods came down off the San Francisco Peaks some 50 times, threatening hundreds of more homes. A massive detention basin stands between the brunt of the water flow and those homes now. And the eastern flanks of the mountains are brown and charred. It’s no accident that Coconino County and the Forest Service chose to demonstrate new technology here, where a stark landscape serves as a sharp reminder that last year’s threats aren’t over. Even as new ones loom. 

"For me the main objective is to show people that we can burn wood cleaner and create valuable bio char to add to the soil to increase soil properties," said Deborah Page Dumroese, a research soil scientist with the Forest Service’s Rocky Mountain Station in Idaho. 

Deborah Page Dumroese
Michel Marizco/KJZZ
Deborah Page Dumroese of the Rocky Mountain Research Station stands against a demonstration of the CharBoss and the Airburner in Coconino County.

A crew rakes a gleaming black sludge of carbon out of an immense machine called the CharBoss. It may sound like the makings of a brisket cookoff reality show, but it is in fact a contained box of hellfire that is designed to reduce wood to its barest essence. 

Page Dumroese calls this an improvement over how overgrowth is generally managed, by  slashing and burning piles and leaving their burn scars on the forest floor.

"We have scars on the landscape that are 50 years old that only grow invasive weeds. So that land has been taken out of productivity," she said.

Coconino County plans to use a system like the CharBoss this fall in heavily wooded Munds Park, a community south of Flagstaff lush with growth. 

"We’re going to bring our machine, burn that all right there on the spot," said Jay Smith, Coconino County’s forest restoration director.

"Mainly where we see the best use for the county when we’re doing community cleanups, we might be able to put this in the community because it doesn’t produce smoke and the community can bring their slash to us letting us burn that slash right in the community," he said.

The Forest Service has been using the CharBoss’s byproduct to repair old logging trails because it restores soil compaction. The byproduct is also being used to revegetate abandoned mine sites because it has a high affinity for heavy metals.

"So using it on places that are contaminated with heavy mercury or lead or cadmium or whatever. It’s nice to be able to tie that up and keep it from moving into water sources or being eroded downstream to reservoirs," said Page-Dumroese.

The first prototype of the CharBoss came out just three years ago. And the Forest Service is testing it in several areas around the country.

The CharBoss is also extremely efficient, says Northern Arizona University forestry professor Han Sup Han.  

NAU forestry professor Han Sup Han
Michel Marizco/KJZZ
NAU forestry professor Han Sup Han stands next to the carbon produced by the CharBoss.

"This machine, you can run year round. Instead of the open burn which has a limited time window," he said.

He points to the CharBoss’s big brother, the AirBurner, whose name belies its purpose: turning roughly a ton of slash piles into a pound of fine ash. 

The Airburner will render three to five tons of slash an hour, and the CharBoss, one to one-and-a-half tons. 

So for now, the systems can be used on a small scale, like in Munds Park where the $160,000 CharBoss will be used in a few months.

Sup Han and other forestry management professionals want to see how these two systems can be used on a scale needed for  the biggest ponderosa pine forest in the world, the Coconino.

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