5 January 2022

Oil-eating mushrooms bring contaminated soil back to life


U.S. researchers test the ability of mushrooms to absorb and break down soil contaminants. A strategy to restore land by reducing the weight of waste

by Matteo Cavallito


Restoring contaminated soil by disaggregating toxic substances and basically solving the problem of disposal: this is the mission of mushrooms, the unsuspected leading players in an experiment that will hopefully set a new standard. The story comes from Marathon County, Wisconsin, where a group of researchers has started a apparently prohibitive mission which involves the local university and the city department of waste management.

The focus of the experiment? Worst thing you can imagine: an oil-loaded block of land. In November, researchers began growing good quality fungi on it. With surprising results.

Researchers’ hope

“Our control soils, if you dig into it, it smells like oil,” Alex Thomas, a University of Wisconsin-Stevens Point researcher involved in the study, explained to a local radio station. Where mushrooms grew, however, the soil “came back smelling really clean — to me it almost smelled like baby powder. That’s an early indication that hopefully we’ll see some results.”

Olfaction, of course, doesn’t provide definitive proof. But scientists now believe that laboratory analysis can confirm the most optimistic hypothesis. The hope, in short, is that fungi could complete their task. That means “cleaning” soil from harmful substances that could have made it unuseful.

More mushrooms means less waste

But how does the natural remediation process work? “Petroleum is a fossil fuel, made of carbon,” local radio station WPR reported. “Mushrooms can feed on the organic compounds and break down the lignins that bond them. Previous studies have shown that they not only remove the petroleum-based contaminants from the soil, but also break them down in such a way that even the mushrooms themselves are nontoxic. You wouldn’t want to eat them, but they can simply be composted back into the now-clean soil.” This does not occur for all composts. But even in the most critical cases, there are some benefits anyway.

In other uses, such as soil contaminated with heavy metals, the mushrooms would become toxic materials that require disposal at the landfill”, WPR says. “But they would take a fraction of the space required to dispose of contaminated soil.”

Thanks to this process it is therefore possible to reduce disposal costs. An important benefit that is attracting the growing interest of scientists in various forms and in different places.

Is mycoremediation the new frontier?

The experiment conducted in Wisconsin is in the wake of a technique known as “mycoremediation“. A practice that is still being researched. “Fungi are nature’s most vigorous agents for decomposition,” says the British Royal Geographical Society’s journal. “For millions of years, they have evolved to exploit the detritus of other species, recycling nutrients through the ecosystem. The only organisms on Earth that decompose wood, their ability to extend through soil in filamentous mycelia, excreting digestive enzymes, allows them to adaptively decompose tough materials”.

Over the years, the journal says, there have been many experiments. Mycoremediation has also been used to decontaminate soils from pesticides. In 2017, moreover, “Chinese researchers isolated a fungus capable of digesting polyster polyurethane.” The effectiveness of these techniques, however, still appears variable and seems to be conditioned by many factors. This is why, the journal suggests, more research will be needed in the years ahead to explore the opportunities of a strategy that remains promising in any case.