Mycoremediation—that is, the use of fungi to clean up pollution—is sometimes put forward as yet another almost magical way that fungi can save the world. Such claims sound too good to be true and sometimes are. Mycoremediation isn’t the sort of simple, one-size-fits-all solution that we might wish it to be.
And yet, properly applied, mycoremediation methods really do work[i][ii][iii].
How Does Mycoremediation Work?
Bioremediation, a broad term covering all forms of using living, or recently-living things to deal with pollution, includes a large number of different techniques involving plants, bacteria, or fungi, or various combinations of these. Once the decision has been made to use bioremediation, the next question is which organism or organisms to use and how. When one of the organisms chosen is a fungus, that is mycoremediation, a process best understood in context as part of bioremediation as a whole.
There are several different ways organisms can be used to clean up pollution: absorption, accumulation, and degradation.
Biosorption
Biosorption essentially involves using living, or once-living material like a sponge to soak up pollutants so they can be removed or at least held in place. Often, dead material works better, especially since it can be used in conditions that would kill living organisms, though a living absorption agent has the advantage of being able to make more of itself. Both plant matter and mycelium can be used.
Bioaccumulation
Bioaccumulation refers to the selective uptake of certain substances by living things. Which substance gets accumulated depends on the species, and it’s not always a good thing for the organism in question. But there are both plants and fungi with a particular talent for safely accumulating one or another type of heavy metal or other toxins—a talent that can cause problems for foragers, since soil with even a very low concentration of toxin can yield mushrooms (or vegetables) with a very high concentration.
How this works for remediation is that if you know what toxic substance has contaminated an area of soil or water, you can introduce the appropriate plant or fungus, trusting it to seek out and suck up the toxin. Remove the snow heavily-contaminated plant or fungus, and the soil or water will be left clean.
Degradation
Degradation here means the breaking up of some complex (and toxic) substance into simpler (and not toxic) component parts. For example, composting solid waste (a process that can include fungi) converts much of the mass into carbon dioxide and water, as well as a small amount of healthy soil. Unlike absorption and accumulation, which only remove toxins—meaning they are still toxic, just somewhere else–degradation actually solves the problem. No more toxin.
Biodegradation agents are not one-size-fits-all solutions. Which toxins a species can neutralize depends on which enzymes it can produce. Some types of waste are the natural food of certain degradation agents—for example, some fungi and other microorganisms are specialized to eat feces while at the same time excluding and killing disease-causing bacteria. These species are a clear choice for biodegradation agents of solid waste. In other cases, a type of waste might not be on anybody’s natural menu, but it chemically resembles something that is. Some fungi are excellent at degrading synthetic toxins because they have enzymes capable of breaking down a very wide range of substances, including some that no bacteria can manage.
Mycoremediation in Practice
To actually use mycoremediation is not as simple as scattering some spores someplace. The right species for the job must be chosen, and sometimes even the right strain—fungi that have been growing in contaminated areas develop a higher tolerance for the toxins they live among, and a better talent for accumulating or neutralizing those toxins, than other strains of the same species have. Mycoremediation agents must often be collected, isolated, and custom-bred for particular projects. Then, too, fungy don’t always remediate alone. In some cases, the best agent for a job is actually a partnership between plants and fungi. In other cases, the first fungus only partly breaks down a pollutant, leaving it still dangerous but accessible to a second species of fungi or bacteria that finishes the job.
Some forms of mycoremediation involve bringing the waste to the fungus in some sort of treatment plant. In other cases, the fungus is introduced to a contaminated site in order to clean it up.
Mycoremediation can be used for many different types of pollutants, including polycyclic aromatic hydrocarbons (PAH), heavy metals, pesticides and herbicides, antibiotics and other medications, pthalates, cyanotoxins and toxic algal blooms, and detergents and dyes. Bear in mind that while there are many fungus species that can be used for mycoremediation, most are only useful for one or two types of pollutants.
Advantages of Mycoremediation
Mycoremediation can work in circumstances where other forms of remediation don’t, plus it is itself non-toxic (apparently this isn’t the case with all forms of remediation, though one wonders why not. How can a process that itself pollutes even count as cleaning up pollution?).
In some cases, mycoremediation projects can also result in edible mushrooms—though it’s important to recognize that not all of them can. Not all mycoremediation agents are edible species. Plus, species that accumulate or absorb pollutants become dangerous to eat even if they would be fine if grown on a clean substrate. And, as noted earlier, some species degrade toxins only partially, leaving some other agent to finish the job. These first-stage remediators could produce mushrooms contaminated with still-toxic substances.
In general, the best bet for duel-function situations involve the use of fungi to process agricultural wastes where the problem with the waste is not so much any inherent toxicity as the environmental impact of the unnatural nutrient load should the material be released. In a way, large-scale commercial mushroom-growing is a form of mycoremediation, since white buttons, criminis, and portobellos (all the same species) are grown in manure, a waste product of animal husbandry that would have to be dealt with somehow, and once the substrate is exhausted for mushroom-growing, it’s perfectly safe to handle and makes a fine soil amendment for gardeners.
References:
[i]Kulshreshtha, S., Mathur, N., Bhatnagar, P. (2014). Mushroom as a Product and Their Role in Mycoremediation.
[ii]Akhtar, N., Mannan, M. A. (2020). Mycoremediation: Expunging Environmental Pollutants. Biotechnology Reports 26
[iii]Stevenson, D. (n.d.). Phyto Myco Remediation Study: Testing Locally-Adated and Sustainable Solutions for Brownfields Cleanup. UCR
