Oyster Mushrooms on Cardboard with No Pasturization

I've been experimenting with oyster mushrooms as of late. I've had some success with mycelium in coffee grounds stored in canning jars. But my success rate with simple alcohol sterilization methods have been low. My main goal is to eliminate the pasteurization process because it is the most energy intensive element. It seems that the transfer process of mycelium and granular substrates have higher instances of contamination. Most of the research I have done indicates that cardboard has a much lower contamination rate. And so I am attempting a system that relies on cardboard with no transfer and am looking for any input on this system. I just inoculated a system and the attached images show what I am attempting.

I took the wet cardboard and layered it with mycelium-rich mushroom stems. I drilled holes outside of the containment box which I wiped with alcohol beforehand. On all the holes I put a layer of wet cardboard. I am hoping that the cardboard becomes well colonized and then I can just punch holes in that cardboard to let oxygen in to encourage fruiting, or if I'm lucky the mycelium will run through it and fruit on its own. I haven't seen a setup like this in my research, but that doesn't mean it hasn't been done... So I just want to throw out some questions for anyone that knows more than I (which is a vast pool). If you have any insight, your thoughts are much appreciated.

1. Does a layer of wet cardboard provide provide the proper O2/Co2 ratio for mycelium to colonize?

2. Do oyster mushrooms bioaccumulate the toxins most likely present in the cardboard adhesives?

3. Do I need to add anything for healthy mushrooms, or is cardboard enough to grow mushrooms on their own (I was thinking about adding coffee grounds when the mycelium has colonized, but is it necessary)?

I'll post updates on this as the experiment continues.

I have read that many people add supplements to add the nutrition but that it greatly increases the likelihood of contamination.

I have mostly been experimenting with light pasteurizing, about 140 to 160 degrees, as it is less energy intensive and reserves more of the substrate for growth of the mycelium.
John S
PDX OR

What substrate are you using? I'm ultimately working toward an off grid system and maintaining a 20-degree temperature variable for an hour can be difficult with a rocket-stove I find. And your point about additives increasing contamination is why I would like to avoid it if possible. But I can't seem to find any information on what the requirements are. From a simple common-sense approach, I figure if the mycelium can grow in a substrate, why would the fruiting bodies need much more?

I mostly use wood chips in buckets. I usually don't add supplements for that reason. I am pretty much of a beginner, so I mostly grow oyster-like mushrooms, as they are easier.
John S
PDX OR

1. The cardboard should be at field capacity. That means no water should be running off of it. Mycelium need oxygen. If the cardboard is over-saturated with water there will be no oxygen for the mycelium to use. Excess water dripping off of cardboard can also pool at the bottom of your container creating a nice environment for competitive molds, bacteria and protozoa. Although oysters will out compete most they will be spending energy on fighting off its competitors rather than growing mycelial mass needed for fruiting/spawn production. I have only been growing mushrooms for several months and have had oysters fight off green mold. I learned from my mistakes, but am still trying to figure out the best balance between least amount of work, least amount of resources and fastest/efficient growth of mycelial mass.

2. Oyster accumulate cadmium and mercury (stamets, mycelium running), but I don't think there are any heavy metals in cardboard. It would be enlightening to have oysters grown exclusively on cardboard tested, but it would cost money.
Personally I would use cardboard as spawn layered in between coffee grinds. My theory is that I wouldn't want to eat meat/eggs/plants that were grown on a substance such as cardboard that has undergone chemical processes and is stuck together with cornstarch (which I don't think is made from organic non-gmo corn planted in polycultures that protect our soil, water and air.) Therefore I would not want to eat mushrooms grown primarily on cardboard. I don't think using coffee grinds is a long-term solution where I live, but for now it is what I am using to obtain a yield. I figure some cardboard gets recycled, most coffee grinds end up in the garbage. The coffee shops around here do not have organic waste disposal for their grinds.

3.Oysters generally should not need supplementing. Martinez et al. (1985) found a yield increase by fermenting coffee pulp for five days and then pasteurizing it(stamets, growing gourmet and medicinal mushrooms). I have had successful colonization of coffee grinds that were sitting around for days by pouring boiling water through them in a large chinois. I then placed the coffee grinds in glass jars and plastic containers until the cooled down. I then inoculated them with stem buts. Of course it would be better to use the coffee grinds after the initial cool down, you could even add coffee grinds gradually one filter at a time. This latter method is more efficient, but if you are not able to be there when the coffee grinds have just cooled down you can still use them.

Other tips/comments:

Have you thought about putting up a moisture tent around the bin. Our house gets very dry in the winter and the outer cardboard might get too dry to fruit, but I don't know what your conditions are.

Alternatives to pasteurization:

1. inoculate in whichever room you have the most stale air.

2. I read a method somewhere online (I can't find the link now) that you can bring all your materials into a room, close the door, don't open it during any part of the process and spray the room with water. Wait until 5-10 minutes until the water drops fall down. The water drops will have absorbed some of the spores and other contaminants in the atmosphere. Your materials should be covered while you do this. After 5-10 minutes inoculate. This is from memory so I could have some details wrong. I think I read it on the forums at shroomery.org, but I can't find it there with a quick source.

3. Another way of avoiding pasteurization is increasing your spawn to substrate percentage. Professional growers using sterile technique use <10% spawn. You could use as higher percentages, but this is less efficient.

4. Look up the hydrogen peroxide method. I haven't used this myself but it is another alternative that seems to work.

Happy growing

Danny Smithers wrote: From a simple common-sense approach, I figure if the mycelium can grow in a substrate, why would the fruiting bodies need much more?

For oysters it doesn't really matter, but for other mushrooms it would make a difference. The substrate upon which spawn is generated is selected for fast mycelial growth and cost-effectiveness. Spawn can then be used to inoculate larger substrates that are more suitable for fruiting. Mushrooms like Lion's mane will be more likely to fruit on sawdust even though the mycelium will grow fine on grain substrate.

Thanks Elliot... Thoughts:

1. I left the cardboard at field capacity, I let it drain so that it was moist and not wet, and so I'm hoping this moisture level works well.

2. I too have concerns about what toxins might be included in the final product, but I think I might spend the money to see what's in the mushrooms if this system works. I am probably placing too much confidence in the cleansing power of mushrooms.

3.I am trying to avoid any infusions beyond the initial inoculation. Mostly because of the contamination potential, so I'm hoping the cardboard will be enough.

... And for the followups:

1. I'm really aiming for a system that doesn't need a room. But I am such a novice, that this reality is very hopeful. I've had success with a jar and no room, but I'm also at a high altitude, low humidity environment that might provide some advantages/disadvantages.

2. This seems like an effective technique, but I really want to develop a "roomless" system.

3. I think this is a very effective technique, the greater the spawn percentage has definitely yielded a better result in my own experience.

4. I have read about the hydrogen peroxide technique, but I'm trying to reduce as many inputs as possible, though it seems effective.

Thanks a bunch for the thoughts. I'll let you know how it all goes.

Also look at lime or wood ash pasteurization. Simple, minimal input, especially if you use wood ash and have a woodstove.

That does look like a promising avenue that I have not heard of, and I do have a wood-burning stove, I'll have to give that a go as well.

Temperature can be measured with a really cheap thermometer too- like $10. That 's what I use.
John S
PDX OR

As I was doing some more research, I happened upon using a fermentation process as well... if it works it seems like it might be the most sustainable considering it requires no additional inputs: http://amateurmycology.com/?page_id=1170

And as an update, it's only 2-days in on the cardboard tactic and the mycelium has begun to run and no signs of contamination as of yet.

I tried that and I couldn't get it to work yet, but I think that someone who is more motivated to work without electricity (off-grid) might take the time to find the important details on how to make it work.
John S
PDX OR

I just wanted to add my two cents...mushrooms are only as healthy as the the substrate on which they grow on...cardboard being of low nutritional quality and watch out for white cardboard for it contains dioxins... and i know some people to us their parabolic solar cooker to sterilize substrates, not sure exactly how but worth exploring.
Also I have successful used coffee grounds from coffee shops with out pasteurizing them myself, they pretty much get pasteurized when they brew the coffee.

I agree Reisha, and my experiment with this really did not pan out. The mycelium started running, but then just puttered out. I've had similar experiences on smaller batches. And I have had success with coffee grounds, but I believe the risk of contamination is much higher in that substrate--the grains are so easy for molds to colonize. I am moving toward straw as a substrate and will attempt to use the cold fermentation process in the future. I've had some success with zero-pasteurization on straw. But it was all done outdoors just to see how it would go. I used purchased spawn in a 5-gallon bucket and it did nicely, until the flies found it, at which time it became maggot food. I've attached a photo of that.

So now I am going to up my experiment and it will probably demand a whole new thread when I get the time. I purchased a full-sized school bus and a city shuttle bus. The school bus will be my mushroom grow room, and the city shuttle will be my spawn room. Each will be have sanitizing entry rooms and will be heated with rocket mass heaters in the winter. I got both of these vehicles for $700 total and they both actually drive--so I couldn't pass it up. There are a lot of design details to work out out and a lot of questions to ask before I put it all together. But if you are interested in seeing how monumentally awesome/fucked-up the experiment turns out, I will post a link here to that new thread when I get it up--probably will be a bit in the future with so much research to do. Out of all the Permaculture principles, slow/small solutions was always the one I struggled with.

Hi Danny,
I am growing oysters in buckets like you are, but I have much smaller holes in the sides, and I cover them with breathable medical tape, so spores don't get in.

I am harvesting white elm oyster (hypsizygus ulmarius) as we speak.
John S
PDX OR

Thanks John, I was always curious about the size of the holes and their effect on the process (insert crude sex joke here). How long do you leave the medical tape on for? And did you remove all of it at once or just as each hole began to pin? If you look at my picture, I had a two-bucket system where I would close the holes by turning the bucket until the straw was colonized, and then would twist the bucket so the holes would match again when the substrate had been dominated. It seemed to work and mold wasn't really my issue, it was the flies. That's why I'm going toward a full interior setup. I will try some experiments with the smaller holes, seems like they produce more aesthetically appealing mushrooms anyway.

I left the medical tape on until the mushrooms pushed it out. I use wood chips usually and I might mix in straw or reeds which I pasteurize. I didn't have any problems with flies. Curious minds want to know why some have flies. I don't know. The tape would make it much harder for the flies to enter and lay eggs, though.
John S
PDX OR

last year i bought 2 bags of oyster wood dowel mycelium. i sanitized a tote . filled it half full of water and a 1/3cup h. peroxide. i soaked about 20 12'' by 16in. pieces of corrugated cardboard. took them out and shook off the excess water then layered them in another tote, sandwiching the dowels in between the sheets. had a few small holes drilled in the bottom for drainage and a few around the sides for air. 3 weeks later the cardboard was completely colonized. i found a moist spot under one of my spruces. i peeled the layers of cardboard and layered them between a few inches of fresh hardwood sawdust. when i was done i had a 15in. high pile of sawdust. i placed a 2in. layer of straw and kept it all moist for 5 weeks. got 3 flushes of oysters from that pile! gonna mix it all up w/ fresh chips and get it going again next spring. doesn't get easier than that!

The maggots are fungus gnat larvae. You can mitigate their effects by using yellow paper strips coated with Vaseline, and harvest early.