• Recent research has found that residual waste from cultivating white button mushrooms can be used to help remove micropollutants from water.
• There have been other examples where fungi has shown promise in breaking down pollutants in the environment, a practice known as mycoremediation.
• Global data platform Dealroom told CNBC that $2.5 billion has collectively been raised over the last five years by 139 mycelium tech/fungi-based startups.

Research into the humble mushroom — an important dietary staple for many of us — suggests that the waste left over from growing fungi could have a surprising sustainable use.

A study by researchers from Utrecht University in the Netherlands found that the residual waste from the cultivation of white button mushrooms can be used to purify water.

"The nice thing about this waste stream is that it has a low value and so, we can make it more valuable," Brigit van Brenk, one of the researchers behind the study, told CNBC via telephone.

The team of researchers explained in the study, which was published in April, that the white button mushroom is among the types of fungi that produce enzymes which degrade lignin — a polymer that has structural properties in wood and plants. These enzymes have also been shown to break down other substances.

The researchers noticed that there hadn't been much use for the substrate left over from harvesting these mushrooms in the Netherlands, with large quantities sent to Germany to be used as fertilizer instead. Substrate acts as a medium for cultivating mushrooms, playing a similar role to soil when growing plants.

With that in mind, the researchers decided to test out how effective the leftover mushroom substrate could be in removing contaminating substances from water. They added eight substances to water, including herbicide chemicals, caffeine and pharmaceutical drugs, and then combined this with fragments of the substrate.

They found that depending on the substance, as much as 90% of these organic micropollutants had been removed from the water across a seven-day period.

'Polluter pays'

In the U.K., in particular, concerns around water pollution have been growing. In findings published last year as part of an ongoing study, researchers from Brunel University London and the University of Portsmouth detected more than 50 chemicals in seawater off the south coast of England, including pharmaceuticals and pesticides.

A 2023 report by the European Union's lending arm, the European Investment Bank (EIB), highlighted that conventional wastewater treatment methods do not fully remove micropollutants. The EIB report also said that the cost of implementing additional treatments to reduce the amount of micropollutants in water was "considerable."

In April, EU lawmakers approved new measures for urban wastewater treatment. This included the introduction of a "polluter pays principle" which means the makers of cosmetics and pharmaceuticals have to contribute to covering the cost of additional treatments for micropollutants. England, however, reportedly does not yet have plans to put in place similar rules.  

Mycoremediation

Another study co-authored by Van Brenk and published in May, found mushroom substrate and a "tea" made by soaking the substrate, could remove textile dyes from water.

More broadly, there have been other examples where fungi has shown promise in breaking down pollutants in the environment, a practice known as mycoremediation.

For instance, fungi has been used in the Amazon rainforest in attempts to clean up oil spills. A grassroots group in Sonoma County, California, turned to oyster mushrooms to deal with toxins in the environment following wildfires. In New Zealand, researchers have used fungi to treat soil contaminated by the pesticide PCP.

Elsewhere, an architecture firm in Cleveland, Ohio, has even backed using mushrooms to help break down abandoned houses in the city.

Lack of investment a 'big challenge'

Given these examples, one might wonder why the use of mushrooms to clean up the environment isn't practiced more widely.

Diane Purchase, a professor of environmental biotechnology at Middlesex University in the U.K., told CNBC via email that a "lack of investment is a big challenge."

"For example, integrating an extra treatment step into an existing wastewater treatment system requires an upfront investment to change the existing infrastructure," she said.

In order to scale up such research to treat larger amounts of wastewater, "a multidisciplinary approach working with environmental engineers and other stakeholders is needed to achieve this goal," said Purchase.

According to Micaela Mafla Endara, biology researcher at Lund University in Sweden, there also needs to be more of a "bridge" linking the research being done in this space.

"I think there is a disconnection between the work being done everywhere because of course there's so many studies, so much work," Endara told CNBC via telephone. Endara was one of the researchers on a study, published last year, that said fungi can have a "vacuum cleaner-effect" on nanoplastics in soil.

Fungi startups

Some startups are already harnessing the biodegrading power of mushrooms to devise solutions that deal with waste. U.S. firm Mycocycle uses fungi to consume and eliminate toxins from industrial waste, to turn it into low-carbon raw materials.

Swedish startup MycoMine has a treatment plant which uses fungi to decompose pollutants that results in biomass, an organic material that can be used as a renewable energy source.

The global data platform Dealroom told that $2.5 billion has collectively been raised over the last five years from 139 mycelium tech/fungi-based startups. That's up from 32 firms operating in this space in 2015. Packaging and textiles are among the other areas where companies have created mushroom-based products.

Van Brenk plans to set up a company with mushroom substrate as the main product.

"Our water is our primary life source ... and if we are destroying our rivers then [we're] probably also destroying our resource for drinking water," she said.

"So this is, I think, a social problem we all face it at this point … our water is our primary life source ... and if we are destroying our rivers then [we're] probably also destroying our resource for drinking water," she said.