• Tom Brain

Making a Steam Generator for Sterilizing Mushroom Substrate

This is a walkthrough of my homemade boiler or steam generator that I use for sterilizing mushroom substrate.


This build features a single boiler with a 2400w element inside. The boiler heats water and blows steam out the hose which connects to the steam drum. The drums are removable and I can wheel the old drums away and connect new drums for the next batch. Everything is covered in open cell foil backed foam. This insulates well and means the boiler doesn't have to run 24/7, just only has to cycle on for about 5 seconds every 20 seconds. It's controlled through a PID controller which keeps the temperature around 95c while it's streaming.

I can fit 22 x 4.2kg mushroom blocks inside. This can perform a pretty decent sterilisation if you run it for 20 hours. I get almost no contamination in my high nutrition mushroom blocks.

This is what I use to sterilize my mushroom substrate prior to inoculation. I do not sterilize my grain spawn with this system as grain spawn is sterilized at 15-21 psi.

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