Fifteen years ago, Danielle Stevenson, a former urban agriculture coordinator in Victoria, British Columbia, began helping the city’s public schools create vegetable gardens. It was interesting work, but there was a major roadblock: When he tested the soil in potential garden areas, he found dangerous levels of lead and other metals, making it unsafe to grow food. Projects will be stopped.
“Nobody knew what to do with it,” said Stevenson, who grew up living and working on farms.
Rather than discouragement, the problem of soil toxicity piqued Stevenson’s curiosity. Eventually, it led him to work full-time in the development of regenerative methods for soil and wastewater treatment. Now a toxicologist and mycologist, some of his favorite tools are fungi.
Stevenson is an expert in the small but growing field of mycoremediation, or the use of mycelium to restore soil or water health. Certain fungi can actually “eat” toxins; their mycelium produces enzymes that degrade other plastics, petroleum, and heavy metals. Mycelium is an underground network of fungal filaments, and the power of this fungal root system is already being seen in some leather and plastic materials, construction materials, and other substitutes for meat.
Although mushrooms have enjoyed a moment in the spotlight in recent years thanks to new techniques like these, mycoremediation still has a long way to go. There may be great potential in using mycoremediation in agricultural settings, but there are still major obstacles to applying the method at scale.
“There’s a lot of talk about the potential of fungi, but most of the studies have been done in the lab and on a very small scale,” Stevenson said.
One of those promising small projects is happening in Marathon County, Wisconsin, in 2021, led by the area’s solid waste department. Alex Thomas, a compost and hazardous waste specialist, was contacted by a machine shop that had accidentally spilled coolant all over a parking lot and wanted help cleaning up. Thomas and his colleagues were waiting for an opportunity to try mycoremediation, and the greasy parking lot was their chance.
A local mushroom grower who is happy with mycoremediation, Jerome Segura, agreed to donate blocks of green and pink mushrooms that had already been harvested for the project. The blocks, which contain the organic matter mushrooms are grown on and the mycelium left after the fruit bodies are harvested, are the waste of mushroom cultivation. The team broke the blocks over the oily soil removed from the parking lot and divided them into three sections: one with pink oyster mushrooms, one with blue, and one without mushrooms. They were pleased to find a 96% reduction in oil waste in the blue area, and a 60% reduction in the pink area.
“It tells us that this is a very simple field method, that with a few more validations, and a systematic approach it could be a viable form of in situ treatment, or at least, a cost-effective treatment for hydrocarbon spills. ,” said Thomas. The experiment involved little intervention on the part of the team: They simply broke the mushroom blocks over the oily soil and watered them a few times, and let the mycelium do its thing.
“This is a good example where we can use existing waste to solve existing problems, and give it a second life and a second use,” said Thomas. “Mycoremediation is really exciting in that aspect.”
Segura worked on other projects with the county’s waste department, including a promising experiment that showed mycelium’s ability to reduce the presence of PFAS in water. But Segura says there’s often a failure to reproduce such studies or publish their findings, and while the federal government has devoted a lot of money to remediation programs, “very little of that money goes to the people doing the work.”
“This work is expensive, and it’s often done ad hoc outside of regular research stations,” Segura said. “As a result, I think many studies and results are lost to researchers.”
Findings from a project that Segura and Thomas did together on spill cooling, for example, were presented publicly but not published in an academic journal.
Some of the biggest studies Stevenson has seen are his own: As part of his PhD research, he identified native plants growing in polluted areas throughout Los Angeles, then planted those with a symbiotic fungus that had previously been shown to remove cadmium and lead from the soil. on three separate three-hectare brownfield sites. A one-year study in these polluted areas showed heavy metals and petrochemicals reduced in the soil, thanks to this combination of phyto- and mycoremediation. Although the results are exciting, Stevenson stressed that the research needs to be replicated and tested further, and scaled up.
“Really, I’m interested in trying to do more of this,” Stevenson said, “trying to continue to measure and test these methods in field conditions.”
One of the obstacles he repeatedly faced was regulatory agencies, which initially blocked his brownfields project. The EPA initially introduced a catch-22, basically telling Stevenson that he could not test a new method in the field unless it had already been proven in the field.
The lack of well-proven methods also makes it challenging to promote experiments with mycoremediation on farms. Because farmers are often “frustrated,” Stevenson says, trying out an experimental method is not a popular exercise. The same concept often applies to city agencies that own sites such as brownfields.
“The people who own or manage those lands just don’t want to try something that hasn’t been proven, even if it can fix the problem and create healthy soil and have all these other benefits and it’s a lot cheaper than others. corrective measures,” he said.
Still, Stevenson remains optimistic, and the broader community of mycologists, mushroom growers, and enthusiasts is pushing forward in North America and around the world. In Germany, mycologist Dietmar Schlosser has been researching how plants and fungi can degrade environmental pollutants for two decades, and has gradually seen more attention drawn to his field in recent years.
“Fungi are known as polymer degraders,” Schlosser said. “Polymers are dense and have to be decomposed into small pieces, and molds are experts at doing that. Considering that with the increasing attention being paid to the destruction of plastics, they are getting more interest now than 10 years ago.”
As researchers such as Stevenson and Schlosser work to demonstrate and document the potential of mycoremediation, there are still many gaps to be filled.
“Fungi are very powerful creatures, and I think we’re just now starting to realize their potential,” Segura said. “We don’t understand how their non-selective digestive enzymes work. Imagine what we might be able to do after understanding those channels and replicating them on a large scale.”
– Rebecca McCray, Ambrook Research
This article was originally published by Ambrook Research, an independent editorial publication supported by Ambrook, a company that makes sustainability profitable in the natural resource industries, starting with providing accounting and financial management software to farmers.
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