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I'm giving oyster mushrooms a go, growing in coffee grinds in a plastic bag. Having an air filter in a bag, like the ones in purpose made mushroom bags, is a recommended technique. What if I used a vacuum cleaner bag ? These allow air passage and also filter out small particles. Workable idea ? I bought some that have a synthetic inner layer that I don't think the mushrooms would consume. What about maintaining a good moisture level by just spraying the absorbent bag ? I'm a noob so let me know if these are bad ideas. Thanks.

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Normally you want to sterilize the substrate in a pressure cooker so those mushroom bags are designed to withstand pressure cooking for the 90 minutes required. I suspect a vacuum cleaning bag is both more expensive than the 60c some charge for mushroom bags and not as robust.

Coffee grinds are insufficient on their own to grow oyster mushrooms successfully. You need more carbon added to the mix.

You need to sterilize coffee grounds as otherwise you'll just grow trichoderma. You don't need to sterilize straw as trichoderma doesn't grow that well on straw and so pasteurization is sufficient. (The same applies to cardboard which can just be boiled.) That leaves enough good bugs alive to combat any pathogens that might want to colonize the straw.

  • I think the bags I got, the synthetic lining might be damaged by pressure cooking, but there are other types, and they are pretty cheap, comparable with 60c. It's an easy experiment anyway. I believe oyster substrate only requires pasteurisation at 80C. Some methods just require pouring boiling water on the substrate and leaving it to cool. I added torn up cardboard to the coffee grinds, mostly to add a bit of space in the mix. I boiled the lot for a while. I didn't know it was absolutely necessary for feeding them too. Can a bag or substrate be microwaved without using too much water ? – Jimmy Widdle Dec 20 '17 at 0:28
  • That's different. I'll add to my answer. – Graham Chiu Dec 20 '17 at 1:40
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It could be working, however I recommend caution, since filtering properties may be very different between the two, even though they look the same or very similar to human eye.

Also, who knows what chemicals are inside vacuum cleaner bags? The problem is that they are supposed to be disposed, nobody predicted mushroom production applications.

All in all, a good idea from the standpoint of creativity, but most likely not so good from practical and safety standpoint.

  • Those are good points, and maybe an email to the manufacturer might answer. What I did do was cut a hole in the plastic bag and tape a square of vacuum bag material over it for ventilation, in an area that doesn't toush the substrate. – Jimmy Widdle Dec 19 '17 at 19:18
  • You need to check the pore size of the vacuum bag material. Mushroom bags use 0.2 - 0.5 micron pore sizes to stop fungal spores from entering. I would think that a vacuum cleaner has an additional HEPA filter to clean the air coming out. – Graham Chiu Dec 19 '17 at 22:13
  • Yeah there must be a lot of different types out there, some will be HEPA. Maybe even those solid box types that come in upright cleaners ? – Jimmy Widdle Dec 20 '17 at 0:29

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