Mushroom Remediation

Chicago, and the Rust Belt more generally, is full of former industrial sites, now-vacant properties that manufacturers gradually abandoned over the second half of the 20th century. The flight of industrial capital for cheaper environs destroyed entire communities of laborers, like the steelworkers on the city’s Southwest Side; it also left residents to cope with the damaging environmental effects those factories created for the earth they worked on. (Of course, there’s also plenty of dangerous pollution still taking place.)

On some sites, the EPA has engaged in remediation, cleaning up the land, air, and water to hopefully allow for other uses. There are also some cases where the EPA has halted work, and, generally, there is perhaps good reason to distrust the Trump administration’s willingness, particularly on a region-by-region basis, to perform the necessary degree of environmental rehabilitation. For those and other reasons, plenty of amateur agriculturists are engaging in their own backyard bioremediation — using living organisms to try to remove toxins from the ecosystems they live and work on.

This week, I want to talk a little about fungal bioremediation. I first heard about it when I read this interview in the South Side Weekly with a farmer about rehabilitating parts of the Cooperation Operation, a big, beautiful community garden in Pullman. The Coop Op was started about half a decade ago; before then, it had been a liquid hazardous waste facility. The EPA did some cleanup on the site — in fact, they settled for around $36,000 with 42 corporations in 2004 to help with waste removal. (In case you’re keeping score at home, or are perhaps wondering about possible causes of widespread civil unrest, that means each company had to pay a little under $1,000, and the EPA waived $200,000 in earlier response costs). Anyway, this farmer decided to ask for public records, and discovered there were still fairly high levels of lead, cadmium, arsenic, and “petroleum-based stuff.” So they decided that they should try their own remediation using mushrooms.

So, how exactly does fungal bioremediation work? Well, to begin with, fungi have, as one academic puts it, “everted stomachs”: whereas we humans decompose our food into nutrients inside of ourselves, in a sac that sits along our digestive system, fungi break down food externally, turning it into nutrients before ingestion. They do this by releasing enzymes into the environment around them through their mycelia — long, branching networks of filaments called hyphae, “the basic fungal unit.” Interestingly, even though larger patterns of growth and reproduction are present in mushrooms, the mycelial networks themselves are protean and indeterminate, forever changing their configuration in response to stimuli around them. (“Determinate superstructure is integrated by indeterminate infrastructure,” is how the mycologist Alan D.M. Rayner phrases this point.) Depending on the extracellular enzymes a particular mushroom releases, they can break down pretty much any substance into simple non-toxic compounds or inorganic matter. Oyster mushrooms have been used to dissolve plastics and crude oil; the splitgill can decompose malachite green; shiitake disappears petroleum compounds.

There are a couple of other processes by which fungi can also remove toxins from an ecosystem. One is biosorption — the removal of substances from a solution or environment by means of biological material. Fungi are particularly useful for this because their cell walls are about 10% chitin, the tough polymer that’s also, as you probably learned in high school, found in the exoskeletons of crustaceans. Chitins have amines, which are particularly good at bonding with metal ions; that makes mushrooms useful in cleaning up pollution from heavy metals. A study that extracted chitin and its chemical cousin, chitosan, from the fungus Cuninghamella elegans found that they could absorb between 25 and 75 percent of iron, lead, and copper from the environment. (And, even if we can’t grow mushrooms in a particular environment, it’s easier to extract chitin from fungi than it is to get it from crustaceans.)

Let’s say you wanted to engage in some backyard remediation (or just, you know, grow mushrooms) — where would you start? The grassroots organization Radical Mycology has put together a helpful guide here. Most fundamentally, you need a really large mycelium, and the best way to get that is by force-feeding the fungus. There are a few different stages here: start the fungal culture in a sugary water broth, move it to a container full of grains (the RM zine recommends rye, wheat berries, spelt, millet, or popcorn[!]), and finish growing it in cooked hardwood sawdust, usually from alder or maple. Once you’ve done all that, you continue growing the mycelium in what the guide calls “bunker spawn” — bags of fermented straw and wood chips. Once they’ve grown in there for a few months, you can use them to filter pollutants out of water, remediate soil, or create stability in any ground threatened by erosion.