Making substrate with coffee grounds

Published on Oct 9, 2021

I drink a lot of coffee and therefore always have this excess waste coffee grounds. Fungi love this, as you will have noticed if you've left coffee grounds out in the open. I've seen it covered in the most oddly coloured fungus, yellow, orange, blue...

Somewhere I read that oyster mushrooms thrive on coffee grounds, so I thought let's give it a shot. I first mixed the brown rice flour and vermiculite substrate to test which works better for this method and made holes in each corner of the tub lids, I now have seven of them in total.

brown rice flour in a white plastic bowl
I made my own brown rice flour because I couldn't find any in the store, using a cheap coffee grinder.
Vermiculite and brown rice flour substrate
Added the water and vermiculite to the BRF and mixed it well

I think the vermiculite I have is a bit too large, will have to find a source of finer verm.

First, I heated up a steel rod which I found lying in the garage (don't burn yourself), placed a lid on the counter over a ridge so that the rod could melt through. Be careful of hot plastic, that shit can give you a nasty burn and get stuck on your flesh.

A white plastic lid with a hot metal rod about to melt a hole in a corner
A numbered lid with the hot rod about to melt a hole in the corner

For the coffee substrate, I added double the amount of coffee grounds to the mix as I do for the brown rice flour. I couldn't really find a good guide online for this, so I will have to figure it out myself which is not a problem. SCIENCE!

Coffee grounds mushroom substrate
If the ratios are not correct, I shall correct it next time.

After all the mixing, I filled the tubs, placed the lids on and made notes in my book about what is in which tub. I then covered them with tin foil and moved three at a time into the pot on the stove to sterilise. The pot only fits three and I have six of these tubs.

What I need to do next, is think hard about how I will fruit all of these. I only have one fruiting chamber and not enough space. Shit.