Hello, I am planning on growing mushrooms in compost substrate. I would like...

Asked November 13, 2019, 7:12 PM EST

Hello, I am planning on growing mushrooms in compost substrate. I would like to soak the compost in water for 1-7 days and then drain the water to let the oxygen kill the anaerobes. However, I know that this liquid / 'compost tea' is bad for plants but I do not plan to use it. My question is: will the liquid that I drain be potentially harmful to myself or any animals that may encounter it? Any insight would be gratefully appreciated.

Franklin County Ohio

1 Response

Hello & thank you for reaching out to OSU Extension with your question. I reached out to Jason Slot, a mycology expert in our Department of Plant Pathology & he as provided the answer for you.
The safety of the drained fluid will depend on a number of factors, but should be treated as potentially hazardous. The "compost tea" should be disposed of in a way to minimize exposure to yourself and animals. Basically, it should be treated similarly to raw sewage because the main threats would be E. coli, Salmonella, and Clostridium. The risk of the compost harboring and amplifying these bacteria will be greater if the compost is made from animal manure, and less likely from plant material. The main concern would be ingesting or being exposed through cuts in the skin. If the work is going to be performed on a small scale, it should be reasonably effective to direct the anaerobic brew into a septic drain avoiding exposure to people or animals. However, if the volume is on a larger scale, it will be necessary to construct appropriate water treatment to minimize unintentional exposures and/or pollution of groundwater. If the fluid is directed to fields that will grow food, time to harvest should be the same as for spreading raw manure (120 days or as locally required). - Jason Slot

I hope that this information has answered your questions.

Kind regards,