Larisa Teslenkova, consultant-technologist, author of the website and YouTube channel “Oyster mushroom expert”.
https://veshenka-expert.info/
https://youtube.com/@oystermushroom_expert-tech?si=WPFm7LUETjL0bDXn
https://veshenka-expert.info/en/oyster-mushroom-cultivation-technology/Teslenkova Larisa,

I believe that in productions growing more than 6-7 tons of oyster mushrooms per month, the raw material should be steam treated to produce a quality substrate.

No matter what kind of raw material you use, soaking in chemical solutions (lime, sodium hypochlorite and some others are used) or hot water treatment are unstable methods when producing substrate quantities of 40 tons or more. In these methods, the substrate is periodically infected and molds or bacteria grow in it along with mycelium of oyster mushrooms. There is also the problem of utilization of production waste – used chemical solutions and used contaminated water.

Steam treatment of oyster mushroom substrate

There are two steam processing techniques that differ in cooking steps, temperature and processing time.

In one case, pre-soaked raw materials are poured into filter bags and processed in unpressurized steaming chambers or pressurized autoclaves.

It’s sterilization.

10 cube autoclave for one load can process up to 3 tons of raw materials (depends on the density of block filling) every day. The work schedule can be organized so that there would be not one, but two loads per day.

The second technology is when the soaked raw material is first formed into bunches and thrown over several times on the site, and then poured by roll into a chamber and steamed with steam at 68-70 degrees Celsius in a ventilated chamber called a “pasteurizer” or “tunnel”. This is pasteurization.

Please note that depending on the capacity and type of steam generator you need, you may need permission from the relevant authorities for the use of this type of equipment (boiler inspection or environmental inspection).

I am not an expert in sterile technology, so I will only describe the pasteurization premises in detail.

However, I would like to note that in order to choose one of these technologies, you first need to calculate all the costs of purchasing the mechanisms, then compare the costs of equipping the clean zone (in sterile technology, the requirements for air purity are much stricter). Then – and this is extremely important – calculate how many years these costs will be recovered. Because on sterile substrates, yields are higher and the variety of raw materials used is much greater.

Facilities required for pasteurization

• 1. The room where the tunnel is located.

For growing 6-8 tons of oyster mushrooms per month, one tunnel with a capacity of 15-20 tons of substrate is enough. If you want to grow a larger volume, you need a tunnel with 30 or 40 tons of substrate, or two tunnels with 20 tons each.

In a 40-ton tunnel it is harder to achieve uniformity of substrate processing, you need a competent specialist who can calculate it. In addition, even with the use of mechanical substrate packing lines, the seeding operation can last two days.

Building two 20-ton tunnels will cost more, but they are more manageable and planning production schedules is more flexible in this case.

The slotted nozzle floors used in mushroom compost tunnels are not suitable for oyster mushroom tunnels. This is my personal opinion – in such tunnels it is very difficult to achieve a quality homogeneous blowing of the entire substrate.

A room with a ceiling height of at least 6 meters is suitable for tunnel construction. The most difficult step in such rooms is to break up the concrete floor to make the tunnel sump.

Usually, tunnels are 3-3.5 meters wide and 3.2-3.5 meters high, and about 2 tons of substrate can be placed per 1 linear meter. Knowing this data, you can calculate the size of the tunnel depending on its loading. The size of the room itself depends on how the substrate is thrown into the tunnel – by tractor, loader, transporter or other method. You will need to determine how much space is needed to install the conveyor belt or to turn the mobile machinery.

Often tunnels are built in a vacant area and then a canopy is made over it and then the walls are completed.

• 2. A shed or room for soaking and flipping substrate.

Its area depends on the machinery used to throw the substrate. A tractor with a bucket throws the substrate to a height of two meters, so it is possible to build structures called “indors” by champignon growers – three walls forming the letter “p”, which allow to form a high pile of substrate. The second way of laying the substrate when shifting – in a pile 1.2-1.5 meters high and no more than 2.5 meters wide. – requires a larger area.

• 3. place for straw chopping (if necessary)

Many companies do not chop the straw, but, for example, crush it with rollers or wheels of heavy-duty tractors.

• 4. Clean area – inoculation room, mycelium preparation room, household rooms. The area of the inoculation room depends on the number of tunnels (as their “clean” gates should go into this room) and on the equipment for packing blocks (what kind of conveyors or loaders are used, whether there is a block of automatic mycelium filling and so on)

There will be a separate article about the clean zone.