I started collecting coffee grounds over a week, kept it moist. Before adding the starter, I microwaved the damp coffee grounds in the hope of killing off anything dormant.

After adding the starter and letting it sit in a basement it now looks like this.

Building the base

I then took an egg carton and old newsprint, dampened them, and again microwaved in for a few minutes to sterilize. I then mixed a bit of the starter in (see smaller container). The smaller container has some cut outs on the side.

enter image description here

This is all a pilot run for me to see what happens. It's all happening in a darkened basement outside of my living space.

My question is am I doing anything obviously wrong or unsafe? Is microwaving wet material before use sufficient enough to preserve the purity of the feed (coffee grounds for the starter and paperboard for the mushroom development)? How would one determine the edible-ness of the final product?

As I said this is a dry run before I run this project. If it fails, I still learn something.

1 Answer 1


Usual method of growing on coffee grounds is to use fresh grounds collected from a coffee shop - if they're fresh, they're already sterile from the brewing process, so not sure whether microwaving grounds you've collected over a period of time would be good enough, it might be. You didn't really need to add anything else, you could just have left the starter to get on with it after mixing it in with the grounds in an appropriate container - more info on the method in the link below


The idea of using a fairly sterile medium is to prevent other undesirables growing in with your mushrooms rather than worry about what the mushrooms will contain when grown. Generally, so far as I'm aware, a non poisonous mushroom doesn't take up poisons which could affect you when eating them as it grows, though it's possible some pathogens present might prevent the mushrooms growing at all or properly, or growth of other things like moulds or algae or the like will knock them out by competing too much.

  • So could I just ventilate the container with the the coffee grounds? Would that be enough to encourage growth?
    – Rick
    Apr 30, 2016 at 14:19
  • Read the link I attached - without rereading it myself, I can't answer that...
    – Bamboo
    Apr 30, 2016 at 15:05
  • From the article, it appears coffee grounds are all that is needed. Mycelium will spread until there is no more food. Then it will begin to produce the fruit to spread spores. Given this, I assume I would assume coffee grounds would be sufficient. Thank you for that wonderful resource.
    – Rick
    Apr 30, 2016 at 16:03

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