Mushrooms to be deployed as a weapon against wildfires in Boulder

Editor’s note: This story was corrected and updated on Feb. 13, 2023.

If Boulder Mushroom achieves what it’s setting out to, the foothills around Boulder could soon sport a whole lot more mushrooms. Fungi could become a major tool for making Boulder’s forests less prone to wildfires by turning branches, logs and wood chips into healthy soil — instead of fuel for future fire they would be otherwise.

Zach Hedstrom is the founder and owner of Boulder Mushroom, a local mycology center that’s branching out to help Boulder combat climate change. Partnering with the Boulder Watershed Collective and Grama Grass and Livestock, Boulder Mushroom recently received a $100,000 grant from Boulder County. The grant — half paid for by the City of Boulder’s Department of Climate Initiatives — comes from the county’s Climate Innovation Fund. Established in 2022, the fund aims to provide seed money for companies trying to tackle climate change and its effects here in Boulder.

In 2021, Boulder Mushroom completed a pilot trial, supported by the Boulder County Sustainable Agriculture Fund, at Ollin Farms which it says demonstrated fungi’s ability to decompose wood chips into compost and hold moisture as they decompose. The trial showed mycelium-innoculated chips holding two to four times the moisture of control wood chips.

What if, he asked, we could use fungus to reduce the intensity of future wildfires across our forests? What if we could use fungus to improve soil health on our agricultural land?

“We’re trying to understand if we can inoculate this waste wood with native fungi and turn it into soil.”

What to do with the cut wood? 

Thanks to overzealous wildfire fighting over the last 100 to 150 years, forests in our state — as in many states — are overgrown. Coupled with drought, this means when fires start and aren’t put out quickly, they burn fast and hot. 

Forest managers in Boulder use prescribed burns and mechanical thinning to counteract this overgrowth. But the risks of prescribed burns, like runaway fires, often make mechanical thinning the preferred option. Such thinning, however, means there’s lots of wood cut from the landscape. What to do with that wood is a conundrum.

Sometimes cut wood is left to dry in piles for a couple years, then burned on a day when snow or other moisture reduces the chance of fire spreading from the piles to the surrounding landscape. Yet there is still a risk of runaway fire, or of providing fuel for future fires if slash piles are only partially burned.

Another solution is putting smaller branches and tree trunks through a wood chipper that sprays them back on the landscape while larger trunks hauled out. Yet such hauling releases emissions from trucks and also removes nutrients from the landscape that would otherwise feed future plants. Wood chips left on the land can provide such nutrients — but they can also feed future fires if they don’t decompose fast enough.

Hedstrom believes he has found a solution to this problem. His hypothesis is that by applying fungi to wood waste, no hauling or burning would be necessary. Fungi — more specifically, fungi’s root-like system, mycelium — would accelerate decomposition, quickly turning leftover wood into nutrient rich soil.

Spreading mycelium over wood waste

Outside Boulder Mushroom’s warehouse, situated near the Diagonal Highway before you get to the Rez, is a pile of what looks like styrofoam blocks. These blocks are actually bags filled with wood shavings and mycelium, or mushroom roots. What most people think of as mushrooms, mushroom growers refer to as “fruiting bodies.” The bags outside the warehouse are the discarded roots of culinary mushrooms sold to chefs around Boulder.

Currently, these bags are bought by local farmers and gardeners to increase carbon and fungi levels in their soils. Much of the land around Boulder is depleted of fungi from excessive cultivation. 

With the innovation grant, Hedstrom hopes to expand this process to restore Boulder’s ravaged agricultural lands while making forest lands less prone to blazes. “We know this has worked at a pilot scale.” Hedstrom said. “We want to demonstrate the efficacy of these methods at a scaled field setting.”

How to best impregnate wood waste with fungus is the question. Hedstrom has a few answers. One would be sprayable fungi. If mycelium is concentrated in a liquid solution, that solution could be put in backpack sprayers to spread fungus over wood waste generated by thinning projects.

Another idea is using bags of mycelium similar to those sold to farmers and gardeners. If one of those bags were put in a wood chipper along with forest thinning slash, the wood chips would be sprayed over the landscape in tandem with fungi primed to decompose them.

A ‘peaks-to-plains‘ initiative

Hedstrom received the Innovation Grant with the Boulder Watershed Collective, a nonprofit invested in forest health projects in Boulder’s watersheds.

Because of the detrimental effects of wildfire on downstream water, Maya MacHamer, who runs the collective, spends much of her time thinning forests to keep future fires at lower intensities. Her projects generate lots of waste wood, wood she’s offering to Hedstrom for mycelium inoculation. The two are also speculating how mycelium can be used to restore land post-fire. 

After fires, the forest service or other entities will often drop wood mulch from helicopters on decimated landscapes to reduce the risk of erosion. “What they should do is have those wood shavings be filled with mycelium,” Hedstrom said. Such a practice would not just prevent erosion, but would help that mulch turn quickly into healthy soil. 

MacHamer calls the Innovation Grant partnership a “peaks-to-plains” initiative. Boulder Watershed works in the peaks, generating wood waste; Boulder Mushroom inoculates that waste with mycelium; and Grama Grass and Livestock — a third partner on the grant — spreads the finished product on the plains.

Andy Breiter, owner of Grama Grass and Livestock, uses grazing practices to try and improve soil health on degraded land around Boulder. “The agricultural world has been so focused on production that it has created land that can no longer produce,” he said.

As a young, first-generation farmer, he’s left to farm “leftover land,” after more experienced farmers secure the better plots. (The land Breiter farms is often city Open Space, which is why the city of Boulder is partly funding this project.)

Compost is one way to slow the demise of degraded land. And mycelium, combined with excess wood chips from MacHamer’s thinning projects, could be a cheaper, quicker compost. Hedstrom could inoculate these wood chips with fungi before Breiter spreads them across his pastures. The healthy soils generated by fungi would then get additional nutrients from cow manure.

Correction and clarification: The original version of this story referenced a study that was carried out by the Coalition for the Upper South Platte. The article suggested that this multiyear lab and field study was connected, however loosely, to Boulder Mushroom’s Boulder County grant-funded project. The article stated that Hedstrom applied for the grant with his partners to see if he could “scale up” what scientists with the Coalition for the Upper South Platte had learned. 

The study’s author, Jeffrey Ravage, after publication, refuted this characterization: “There is no connection between what I am doing and what Boulder Mushroom suggests,” he wrote. Hedstrom, too, after publication, said the study was not part of his grant application. (As part of his work, Ravage started the Coldfire Project, described as “a group of researchers and practitioners who collectively have decades of experience in fungal degradation and environmental restoration/remediation.”)

As such, the mention of Ravage’s study has been entirely removed. The article now mentions a different study completed by Hedstrom with the help of Boulder County. 

Further, the original version of this article suggested that theoretically more mushrooms would be available in the Foothills for foraging, as Hedstrom is only cultivating edible varieties. This was removed, as it is unlikely there will be an increase in fruiting bodies.

Finally, a sentence was removed because it suggested the mycelium from Hedstrom’s warehouse put onto farms forms a symbiotic relationship with plants. In fact, fungi that form symbiotic relationships are different from those that break down wood chips.