A broad overview of the lessons we’ve learned farming mushrooms.
We started out buying colonized blocks from a popular mushroom distribution company online. Our intention was to grow in a Martha Tent (I linked to GroCycle’s page, they’re a great resource for growing mushrooms in general). This gave us a small space to control humidity and temperature. We used an Ultrasonic Puck (like what they use to make fog in haunted houses), a computer fan, and a tote of filtered water to raise the humidity to above 80%, then relied on passive air exchange to grow a couple of blocks at a time. We monitored it through Home Assistant (an awesome tool that we still use for a lot on our farm, it deserves it’s own series of posts). This worked ok, but cleaning had to be constant to keep from having mold issues, and we ended up breaking the first CO2/Humidity sensor with how high the humidity was constantly. The sensor was an ESP board sensor that I had soldered together. We really didn’t like the repeated single use plastic waste that came with ordering colonized blocks online, so this stage was pretty short lived.
Searching for Sustainable Mushroom Farming
We’ve been through several full operation changes to find the best way (for us) to bring mushrooms to the market. I’ll briefly explain what we’ve tried, then I’ll elaborate on the things that we’ve found work well. First of all, we’ve tried a few different sources for our genetics. We are currently using Master Cultures sourced from The Mycelium Emporium. We’ve found their genetics to be reliable and strong. We started with soaking and simmering Rye Berries to hydrate them, cooling them on a dedicated (newly purchased) window screen over a 22 gallon tote tote.
Loading that into 1qt Mason Jars, pressure cooking them to sterilize the Rye Berries, then using that grain to make grain spawn using liquid culture.
We’ve tried different kinds of sugars for our LC, high fructose corn syrup, honey, etc. The best we’ve found is Dextrose, which we supplement using Light Malt Extract. To this day, this is the recipe that we use for liquid culture:
Liquid Culture: 1g light malt extract (dextrose) per 600 ml of filtered or distilled water
We keep our liquid culture in 1qt ball jars with a magnetic stir bar, then we use a self healing injection port and a filter patch on top. We use a Magnetic Mixer to regularly stir our LC so that it stays evenly distributed. We use a step up bit and a hand drill for a lot of our builds.
This worked well for making grain spawn, but the Rye Berries were hard to source and expensive in our area. This lead to us testing a lot of different grains. Popcorn worked great but was very expensive in comparison to other grains, field corn was cheap and dirty but worked pretty well, milo needed washed a lot and was quick to burst during the simmer. We used field corn for a long time before we found White Proso Millet.
It’s relatively cheap where we live for a 50 lb bag, we buy it from a Co-op that’s 10 minutes away from our farm. The amount of inoculation points that you get in comparison to corn makes a huge difference on the colonization time of your block.
I’m getting ahead of myself though, while we were still using rye berries and corn our goal was to cold pasteurize straw with lime, then reuse food safe buckets to produce weekly yields. The yields we were getting vs the amount of time it took to pasteurize the straw in onion bags just didn’t make sense. The water that the straw would soak in had a terrible straw odor the next day. It just didn’t compare to the colonized bags that we were purchasing from other farms, so we knew we needed to pivot.
We discovered that Unicorn Bag makes Oxo-biodegradable Bags (which degrades from oxygen), they were just a bit more expensive than the plastic unicorn bags. This lead to us making our first real upgrade, which was going from pressure cooker to autoclave and establishing a method for our lab work. We ended up with a 12″ x 12″ flow hood to do our lab work in front of. At this point the decision had been made that we were going to go from hobbyist to trying to build something commercially viable.
We painted the floor of our garage with Kilz, which is a mold and mildew resistant paint. We took thick plastic from Home Depot, ripped 2×4’s into 2×2’s, and built two rooms in our 4 car garage. We built a lab space, and a colonization room and supplied both with shelving. The rooms have inline fans blowing through them, we use 4″ inline fans, with a filter going between our lab space to our colonization room, then another filter from our colonization room out into the main room. The idea is that you want to maintain Positive Pressure in a filtered environment when you are doing lab work to keep contaminates from settling in your workspace. Ideally you want the environment to be as clean as possible to prevent losing supplies to contamination. This seems to be the common workflow for commercial mushroom farms, depending on what your goal is.
Sourcing Genetic (via Spore or Distributor) -> Sterilize Agar or Liquid Culture -> Develop Genetic through plate work or inoculate LC to grow genetic stock
Sterilize Grain -> Inoculate Grain from LC or Grain to Grain transfer -> Sterilize/Pasteurize Substrate -> Substrate Inoculation from Grain Spawn -> Substrate Colonization -> Fruiting -> Harvest and Sales
Around this time we took a lot of time to learn about plate work and agar cultures, “cleaning up” genetics that you buy, and agar slants for long term storage. They are good skills to have in maintaining a library of high quality genetics. We may talk about what we’ve learned related to cultures in future posts, but it’s a large topic itself. We also learned about senescence and the biological lifespan that mycelium inherently has. If you’re not familiar, senescence is an important concept to become familiar with in growing anything.
Keeping the work flow in mind, you want your work space to flow from the least clean to the cleanest environment while you work. Starting with Sterilization/Pasteurization (where it’s got dirty grain, and your substrate ingredients, and where you will end up making your bags, which leads to the lab space that you can wash your hands then move your sterilized bags to, which leads to our colonization space, which leads out to the main area which holds our fruiting tents, and finally the harvest area where we weigh the mushrooms and either box them or bag them depending on where they are going. Considering this structure doesn’t really change, just the equipment that you use, we’ll go through what each section entails.
Substrate and Bagging
All of the mushrooms that we grow are Saprotrophs, which means they attain their nutrition from decayed organic matter, in our substrate that matter is hardwood and soy hull pellets. We source our Soy Hulls from a Co-op just down the road. Our hardwood comes from pellets used for smoking meats. We try to use Oak where we can, but we’ve used fruit woods without issue. Hickory has shown to cause issues, so if we have to get a mix we avoid mixes with Hickory. We are in pursuit of a local mill that has Hardwood, but so far we haven’t found one without Hickory in the mix.
A 50/50 mix of hardwood sawdust and Soy Hulls is commonly referred to as Master Mix. This substrate mix is what most of our mushrooms are grown on. The only real exception right now is Shiitake, which needs less nitrogen supplementation, so it is grown on a mix of Wheat Bran and Hardwood sawdust instead. I will provide our recipes for both in this section. With this dry mix, you will need to add water to reach a hydration rate of about 60%. We went through the process of trying to just add the dry pellets with the right amount of water to our bags, then letting them soak for about an hour, then mixing them in the bag before sterilizing. We found that this caused hydration issues and inconsistency when it came to mycelium growth. There was a huge difference in our bags when we switched to adding everything to a tote, then hand mixing it until it had a consistent texture through the mix. With two 25 quart autoclaves, we do 16 unicorn bags (Type 10A-OxoD) a week. That gives us 4 bags with 10 lbs of substrate per day throughout the week, then we do grain on Fridays. We now use 14A OxoD bags for our grain as well, to save time on washing glass jars. With us doing 4 bags a day, we’ve found mixing to be way easier by using a 5.3cu Ft Concrete Mixer.
So our SOP for making master mix:
To fill one 10A-OxoD Unicorn bag we use 964g of Soy Hulls, 964g of Hardwood Pellets, and 2,870 mL of water. This gives us 10 lbs of hydrated substrate in each bag.
We usually do 4 bags at a time, so we will do 3,857g of Soy Hulls into the concrete mixer, 3,857g of Hardwood Pellets into the concrete mixer, 11,480 mL of Reverse Osmosis water into the concrete mixer, then mix for 30 minutes. When we come back to it, it’s usually sticking to the walls of the concrete mixer, so we put on some nitrile gloves and pull it off of the walls. We then dump it into a tote, and load our bags on a postal scale until they weigh 10lbs a piece. We also label our bags at this stage with their batch number and the date. Bags are then loaded into the autoclaves.
If we are making blocks for Shiitake, the recipe looks like this instead:
To fill one 10A-OxoD Unicorn bag we use 1,344g of Hardwood Pellets, 336g of Wheat Bran, and 2,600 mL of water. This gives us 9 lbs of hydrated substrate in each bag. We found 10 lbs made it hard to work with the bags during inoculation due to how full they are.
Sterilization
Like I mentioned before, the most reliable method of sterilization at this price range that we’ve found are the autoclaves that we use. They have an automated shutoff, and they’re incredibly easy to operate. We run them at 122C, and we haven’t had any contamination issues since we’ve been using them. There are different timings depending on what you are sterilizing. Here’s what we typically follow as a guideline:
LC and Agar: 15 minutes at 122C
Grain and Substrate: 3 Hours at 122C
The timer tops out on these at 99 minutes, so we set the timer for 90 minutes, then restart it as it finishes for 2 cycles per run. It takes a little bit of our attention, but the return is well worth the effort.
The upgrade from this, and the transition we are currently in, is to an Atmospheric Sterilizer. The best option from our research seems to be Bubba Barrels atmospheric sterilizers. Having ordered one from them ourselves, their customer support seems easy to work with and setup seems easy. The smallest barrel (55 gallon) claims to be able to handle 200 lbs of substrate, so 20 of our 10A bags in one cycle.
Lab Work and Colonization
Not including genetic maintenance, the typical lab work for mushroom growing is done in a clean workspace. A lot of people will use Still Air Boxes or just do their work in a positive pressure room. The best environment is a Hepa Filtered room with positive pressure and a Laminar Flow Hood. I mentioned that we started with a 12″x12″ flow hood, which got us through a lot, but we currently work with much larger flowhood and the upgrade has been substantial. The additional power of the fan helps maintain positive pressure in the room while working, and the added work space area makes keeping things clean much easier than with the smaller flow hood.
The time spent in the lab in the typical workflow includes either inoculating grain with Liquid Culture based on the genetics we want to grow, doing grain to grain transfers (where you inoculate grain with grain spawn that you have previously colonized, usually 1 grain bag is good to produce 10 more grain bags in a grain to grain transfer) which seem to move a bit quicker than liquid culture with the caveat that the genetic can degrade over multiple transfers causing drops in yields and growth speeds, and inoculating sterile substrate with colonized grain spawn. We are in the lab at least once a week inoculating the 16 substrate bags and 6 grain bags that we produce weekly.
Once we have the bags inoculated, they go into a separate storage space where they sit on shelves until they are colonized. This can take a couple weeks, or this can take a couple months depending on what the genetic is. Oysters move pretty quickly, Freckled Chestnut and Lions Mane are a little slower, Shiitake takes a long time. It’s important to learn about how to tell when your block is colonized and ready to go out. If an Oyster block stalls, for example, then it could start fruiting before it’s fully colonized. This just lowers the biological availability and hurts your first flush yield.
Fruiting
This part of the process has a lot of nuance and a lot of room for error. The big key factors here are, good air exchange and exhaust, heavy humidity control, and maintaining a clean environment. We’ve set it up a few different ways to try to find what works best, I will break down how we have ours set up now:
4’x8′ Grow Tent as a base. We use 23 Gallon Totes for a lot around our farm, we usually buy them from Home Depot or Sams Club. In this case, we set the tote outside of the tent. The Tote has two holes drilled into the top, one has another 4″ inline fan with a vent tube going into the tote. The other hole has a vent tube going to an exhaust hole at the top of the tent. Inside the tote is a UV Sterilizer light and an ultrasonic puck. The Ultrasonic Puck and the fan is connected to an Inkbird Humidity Sensor that is set to keep the relative humidity above 80%. So the tote produces mist when the sensor kicks on, the fan pushes air in with the mist to the top of the tent, then we have another vent tube that pulls air from the bottom of a tent all the way outside using another 4″ inline fan. The exhaust fan (the fan pushing out) is always running so that we have constant Fresh Air Exchange in the tent.
Inside the tent, there is room for about 4 metal shelves. You can see below that we use something similar to these:
We also have some cheap LED shop lights to provide light to the blocks as they fruit. Those run 24/7. Fruiting mushrooms is genetic dependent. Oysters fruit quickly, usually in 5-7 days. Freckled Chestnut take more like 21 days. Lions mane can take closer to 14 days. We will try to cover specific genetics in the future.
The rooms need cleaned regularly. We typically clean with Hydrogen Peroxide or a diluted bleach solution between grows.
Harvesting and Packaging
Each genetic has a very specific, usually short, window for peak harvest. For Oysters as an example, the caps wills curl or spores will drop and it will be too mature for most. The flavor will change, the texture will toughen or get a slimy texture to it. Pink Oysters will start to turn white. Mushrooms like the Princess Pearl or Blue Oysters might start to have their caps crack when they are over mature.
For our packaging, we stick with biodegradable packaging. We use open faced cardboard for restaurant and grocery store deliveries, then brown paper bags for smaller deliveries or for farmers market purchases. We had custom stamps made with our logo, then a stamp for each type of mushroom. We have different colored inks for the different types of mushroom. This was a cheap and effective way to get our branding onto all of the bags as we sell with them.
We prefer to sell full clusters over breaking them down into clams shells. They seem to have a longer shelf life. They have more shelf appeal at Farmers Markets this way too.
If you’ve ready this far, I appreciate your time. Hopefully it helped to some extent. This should get you to the point where you are growing about 30+ lbs of mushrooms per week.