The Walden Effect: Farming, simple living, permaculture, and invention.


Oyster mushroom on jeansPreviously, I've written about how we can grow mushrooms to eat, but mushrooms are good for a lot of other purposes.  For example, King Stropharia seems to attract worms, so the spent substrate is great fodder for the worm bin.  Other fungi in the soil team up with plant roots and help them suck up water and hard-to-find nutrients.  And now that we've started terrorizing our landscape with toxic waste, scientists have discovered that fungi are even capable of cleaning up our messes --- mycoremediation.

Mushrooms are voracious, and Tradd Cotter has found species that can chow down on E. coli and Salmonella, suck up lead, mercury, arsenic and other heavy metals, and break down chemicals into non-toxic compounds.  The trick to using mushrooms to deal with these contaminants is to find the right species for your problem.  For example, morels and puffballs are great at absorbing heavy metals, but they won't touch coliform bacteria with a ten foot pole.  Luckily, King Stropharia and turkey tails fill that niche.  Oyster mushrooms can break down 80% of DDT in 28 days and the aptly named "Train Wrecker" fungus can eat through railroad ties impregnated with CCA.

MycoboomSo, how do you get your mushrooms to clean up your mess?  Mushrooms don't grow directly in soil or water, so you have to find a way to mix your substrate into the contaminated area.  The most common method is to inoculate wood chips or straw with your mycoremediators and put that substrate on top of the problem soil or where the contaminated water has to flow through it.  If you want to go high tech, Tradd showed us pictures of floating mushroom islands that are let loose in lakes to clean up sullied water.  At the other extreme, you can just put the raw substrate on top of contaminated soil and eventually the right fungus will show up and get to work.  (This image is a Mycoboom that Paul Stamets developed to clean up the oil spill in the Gulf.  Too bad the powers that be wouldn't let him use it.)

However you match your fungus up with the contaminant, you have to think a little differently to grow mycoremediators compared to growing edible mushrooms in your backyard.  In most cases, fungi deal with contaminants by secreting enzymes that work like an inside-out stomach, digesting the world around them so that the fungi can suck up the nutrients they're looking for.  Your fungus won't be breaking down DDT while it's putting its energy into producing mushrooms, so you want to keep your mycoremediators actively growing rather than changing over to fruiting mode.  That means you want to keep adding more substrate so that the fungus doesn't hit a wall and figure it's time to fruit and sent its kids off to explore a larger environment.

Mushroom eats oilI came to Tradd's talk on mycoremediation for one reason --- to find out if and how I could use fungi to eat up the glossy paper that has no other use on our farm.  He recommended trying oyster mushrooms on the paper, but couldn't answer my question about whether the resulting fruits would be safe to eat.  In general, you can eat the mushrooms that grow as part of the mycoremediation process, but not if your fungi have been chowing down on heavy metals since fungi break down most contaminants into non-toxic byproducts but just act like dynamic accumulators with heavy metals.  As best I can tell, glossy paper might contain clay (tough on your compost pile but probably fine for mushrooms), calcium carbonate (no problem), petroleum-based inks (no problem, says the fungus), and chromium, lead, and cadmium.  The last three are heavy metals, so, unfortunately, it sounds like our glossy paper will continue to go begging on the homestead.  Back to the drawing board!

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This post is part of our Low Tech Mushroom Cultivation lunchtime series.  Read all of the entries:

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About us: Anna Hess and Mark Hamilton spent over a decade living self-sufficiently in the mountains of Virginia before moving north to start over from scratch in the foothills of Ohio. They've experimented with permaculture, no-till gardening, trailersteading, home-based microbusinesses and much more, writing about their adventures in both blogs and books.

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I don't think you have to worry about heavy metals in printing inks these days. Lead (white) and cadmium (yellow) as pigments were phased out decades ago, to the best of my knowledge. Titanium dioxide (white) is the most used pigment in the world, and is pretty much harmless when suspended in an ink or paint. Chrome(VI) is still used in chromate conversion coatings, but these are being phased out. I cannot imagine it still being used in inks.

Both vegetable and mineral oil based inks use metal compounds as catalysts for the "drying" reaction (polymerization/oxydation, see drying oils).

You can find an overview of the usage of metals in printing inks here.

Comment by Roland_Smith Fri Mar 18 13:58:51 2011
I was hoping you would chime in! That does make it sound like we might be alright. The only thing that makes me leery is that I'd be using all kinds of glossy paper from various sources, so I can't check with anyone to be sure the paper is heavy-metal-free. I might be tempted to try it, and then dry the mushrooms and send them off to a lab to be tested. Not sure how much that would cost, though...
Comment by anna Fri Mar 18 19:46:45 2011

You cannot be sure about a lot of things. E.g. the natural level of heavy metals and other pollutants in the soil in your garden.

Your land could have been used in the past for copper smelting or other metal working by native americans or the first european settlers. In the case of copper that would leave copper and arsenic contamination. Or there could have been some industrial activity (tanning?) upstream on your creek.

I'm not sure what method to use for detecting all heavy metals. Mass spectroscopy perhaps? I doubt it is something simple and cheap, though. But you'd really have to ask someone who has properly studied (inorganic) chemistry.

Comment by Roland_Smith Sat Mar 19 03:50:01 2011
Excellent points. I probably just have to trust, at some point, that things are relatively in balance.
Comment by anna Sat Mar 19 07:33:25 2011
I am especially fond of this line of posts. I don't remember where I first heard about wonders of Fungi and the potential for mycoremediation but I have been highly interested in the topic for some time. I know one of the first places was the AgroInnovations podcast. With all the oil and gas industry here, there is a great deal of contaminated soil in need of remediation.
Comment by SoapBoxTech Sun Mar 20 01:48:40 2011
Mycoremediation does seem to have a huge potential. I was reading an article about fungi being used to clean up oil in the Amazon. Pretty amazing!
Comment by anna Sun Mar 20 09:08:56 2011
Any ideas what to do with the mushrooms after you use them for remediation? For sure it cannot be eaten especially if heavy metals were remediated so what will be the use of the mushrooms? Can you use them for making organic fertilizers? Are you not returning the toxic substances in the soil if you do that? So how do we dispose of the mushrooms used in remediation? Thanks :)
Comment by yuri_ph Thu Jun 16 23:29:10 2011

That's an excellent question. The great thing about mycoremediation is that mushrooms break down toxic substances (with the exception of heavy metals) into non-toxic products like sugars, so you can go ahead and eat the mushrooms. On the other hand, if you're really using them for mycoremediation primarily, you'll want to keep the fungi in a vegetative state so they'll do more work, in which case you won't have anything to eat and will just get richer soil as a result.

The one exception is if you're using mushrooms to deal with heavy metals. They'll just concentrate the heavy metals in their bodies the way some plants can do, so you'll have to remove the mushrooms and dispose of them somehow.

Comment by anna Fri Jun 17 08:36:03 2011
Comment by AJAYI Tue Jul 10 06:24:10 2012
Ajayi --- Unfortunately, I don't have all the data, so you'll need to do some research to figure out the right species for your specific contaminant. The article and comments above explain the biology behind why you can eat the mushrooms from certain contaminated areas and not from others. Good luck!
Comment by anna Tue Jul 10 09:23:29 2012
anna you are very wrong about eating mushrooms that have been used for bioremediating heavy metals. do not eat them!!!!
Comment by kyle Thu Sep 27 22:05:09 2012
kyle --- I think you misread my post. I wrote "In general, you can eat the mushrooms that grow as part of the mycoremediation process, but not if your fungi have been chowing down on heavy metals..."
Comment by anna Fri Sep 28 07:50:34 2012

hello gud day...

Your topic really interests me, it gives me and my fellow group mates an idea that your study could help us in our undergrad thesis. Spent mushroom compost of pleurotus sp. will be used in our study as a bioremediant of heavy metals in soil..can you please help us in our methodology?..we have some question regarding the container you used in the study?the capacity and the percentage? Did you use live mycelia of mushroom..and what type of species of mushroom dd you use specifically?aside from that, how did you introduced the soil sample in your study..

Comment by ICAH Sun Dec 9 04:05:40 2012
ICAH --- I'm afraid I'm only reporting on other people's experiment here, so I can't answer any of your questions. I recommend you go right to the source --- Tradd Cotter at and Paul Stamets at
Comment by anna Sun Dec 9 07:59:39 2012

I will like to know the conditions required for the growth of d mushroom after its been used to augment the contaminated soil. Is it possible to introduce the mycelium into d soil?

Comment by Kaylad Mon May 6 20:55:11 2013
Kaylad --- That will depend on which kind of mushroom you're growing. In general, you'll use the same techniques to grow mushrooms for mycoremediation as for producing food, except that you'll try to keep the mushroom in the vegetative-growth stage and may not eat it.
Comment by anna Tue May 7 09:07:54 2013
So let's say mushroom did the work and they also absorbed some heavy metals and are not edible no more so we must get rid of them. do you think they could still be used for beta glucan extraction for example?
Comment by Berg123 Fri Dec 4 16:37:44 2015
Berg123 --- I'm afraid that's beyond my skill level to answer. But Tradd would probably be able to answer your question. His contact information is on his website at
Comment by anna Sat Dec 5 10:38:05 2015

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