Creating a Template for Mushroom Farms

In light of my attempt to start a commercial mushroom farm, I have been vigorously consuming various mushroom related content through YouTube. Among these videos, I have been interested in tours of mushroom growing facility. These typically walk the viewer through the mushroom production facilities, giving them a picture of the inner workings of how mushrooms are cultivated.

Despite the seemingly large variations in mushroom facilities, however, the main processes are mostly identical across all farms.The main processes that take place in the facility (so not counting sourcing and selling) I have identified are as follows:

1) Hydrating and mixing substrate

2) Sterilization and inoculation

2) Colonization

3) Fruiting

Phase 1 - Hydrating, mixing, and bagging substrate

Smaller growers typically hand mix up to a hundred pounds of mushrooms a week, which can be produced only by inoculating maybe twenty ten-lb bags of mushroom weekly. However, at a certain scale it becomes infeasible to hand-mix substrate so they are a variety of machines that can be purchased which facilitate the process. These machines will mix and hydrate the substrate at its required ~60% hydration level, which significantly reduces human labor. I would think that a grower would need to get to the point where they are producing at least hundreds of pounds a week, however, before this becomes a need.

Then the mixed substrate can be bagged into plastic bags (or other containers depending on the growing method). This is also mostly done by hand by smaller growers, but there are a number of machinery that exists to help automatically fill bags. However, these machines also make more sense once a grower has hit the level of at least a few hundred pounds of week.

Phase 2 - Sterilization and inoculation

In order to grow mushrooms, the substrate used as the final growing medium, usually a mixture of hardwood pellets and nutritional supplements such as soy, must be sterilized. Additionally, if grain spawn is being created in house, it is also required to be sterilized. This dramatically increases the chances of success with inoculation. In the absence of thorough sterilization, the mycelium will compete with other molds or bacteria and will experience reduced growth if not complete failure.

Typically, small to medium mushroom growers rely on household pressure cookers, or if larger, big autoclaves or custom-build steamers. These elevate the temperatures to around 220F for around two hours, which is enough to kill off most-contaminants. Certain species of gourmet mushrooms may require more sterile conditions for successful inoculations.

In particular, growers should be extremely careful to achieve sterility during inoculations. Inoculations must be done in a clean area under a laminar flow hood, which pushes out clean air over the working area. Any surfaces worked on, tools used, and gloves should be sanitized with 70% isopropyl alcohol or be fresh out of the packaging before usage. To reduce the risk of air-borne contamination, inoculations should also be done as quickly as possible. Then an impulse seal can be used to create an air-tight seal at the mouth of the bag. Once sealed, the bags can be handled more freely as they are at minimal risk of contamination.

Phase 3 - Colonization

The colonization phase is the most straight forward and at this point the bags don't have many needs. They should be stored in a dark area and can be packed tightly onto racks where they will remain until the mycelium successfully colonizes the entire bag. They do not require humidity control - unless the air is exceptionally dry in which case a small humidifier raising the percentage to around ~50% may be helpful.

In medium scale facilities where up to a thousands of pounds are grown a week, many growers recommend racks with wheels as fully colonized bags can be directly carted into the fruiting rooms, which saves time on manually moving bags over one at a time.

In cases where thousands of pounds are being produced weekly, it may be helpful to include a fan in the grow room as the mycelium emit heat as they colonize the substrate. In low numbers, no cooling mechanism is needed, but with hundreds or thousands of bags, they can generate substantial heat, which may warrant cooling.

Phase 4 - Fruiting

Arguably the most complex phase is the fruiting phase, where temperature, air flow, humidity, and lighting must be controlled perfectly to maintain ideal fruiting conditions for a given species. The fruiting area typically takes up a sizable portion of the facility and is the busiest as inlets and outlets for fresh air, water, and lighting must be connected.

Most established growers seem to make or re-purposes specific rooms to water-proof them and and thread-in the necessary tubing. So in a typical fruiting room, there is an inlet for fresh air, an exhaust for spent air, fans for air circulation, an intake for humidified air, lighting emitting 200 - 500 lux across the entire room, and racks for the mushroom bags. The exact set up differs from grower to grower. Many beginners start with insulated grow tents which can provide all the above while having the advantage of being portable to another facility should they eventually move.

Ideally, one would have at least two grow areas (in sq footage) for one area for colonization. This is because mushrooms that are fruiting take up significantly more space as opposed to bags in the colonization phase which can be packed tightly together.

Growers should also be careful of contaminants and clean their grow rooms daily, then do a deep clean after each major harvest as creating an ideal environment for mushroom growth also encourages other mold or bacterial growth which can suppress the mushroom growth. As emphasized by various growers, the utmost attention should be paid to maintaining cleanliness in the growing tents. This will save much time and headache in the long run.

Conclusion

Ultimately, the complexity of mushroom farming can really be boiled down to the above four steps. Naturally, there is variation in the above. Certain growers may favor different mixes of substrate or use different forms of grain spawn. Not all growers rely on pressure cookers or steamers for sterilization and may just pasteurize their substrate by mixing it with hot water or increase the PH with hydrated lime, especially if they are growing more aggressive strains such as oyster mushrooms.

Nevertheless, all mushroom farmers will be familiar with the above four stages and will have worked to sort out problems relating to all of the above. Therefore, it is a good structure for thinking about how mushroom farms function.