Zach Hedstrom of Boulder Mushroom stands by discarded mycelium. Local farmers purchase the mushroom roots to increase the fungi levels of their soil. Credit: Tim Drugan

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.

A pilot project has shown promise that mushrooms can turn wood chips into compost. Hedstrom applied for the grant with his partners to see if he could scale up what worked in a lab. 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 system, mycelium — would accelerate decomposition, quickly turning leftover wood into nutrient rich soil.

Bags with mycelium at Boulder Mushroom inoculating wood shavings. Credit: Tim Drugan

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 fungi levels in their soils. Fungi form symbiotic relationships with many plants, helping them obtain nutrients and protecting them from disease. Much of the land around Boulder is depleted of fungi from excessive cultivation. 

With the innovation grant, Hedstrom hopes to scale up this process to restore Boulder’s ravaged agricultural lands while making forest lands less prone to blazes. “We know this has worked in labs,” Hedstrom said, citing a study done by the Coalition for the Upper South Platte. “But it’s never been tried at scale.”

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.

A boon to foragers

Fruiting bodies forming off the mycelium bags in Hedstrom’s grow chambers. Many shown here are Lion’s Mane mushrooms. Credit: Tim Drugan

The benefits of mycelium to the landscape make it easy to forget the flowers they provide. But mycelium is, after all, mushroom roots. And when deciding which strains of mycelium to use, Hedstrom chose only those that produce edible fruiting bodies. 

“This one is called Neolentinus ponderosus,” Hedstrom said, pulling a bag sprouting with mushrooms out of his humid grow chambers. “It’s a pine rotter.” It’s an edible pine rotter that prefers ponderosa pines —the trees most plentiful around Boulder.

So theoretically, if Hedstrom and company’s work goes as planned, on a rainy week a few years from now — as fruiting bodies form in humid conditions — a hike around Boulder could also become a forager’s dream. Edible mushrooms could cover the landscape, providing food for Boulderites and the assurance of health underfoot.

Tim Drugan

Tim Drugan covers wildfires, water and other climate change-related issues for Boulder Reporting Lab with a focus on explanatory and solutions journalism. He also is the lead writer of BRL Today, our morning newsletter. Tim grew up in New Hampshire and graduated from UNH with a degree in English/Journalism.

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