Substrate for Mycology: A Comprehensive Guide on Using Coffee Grounds

PROCEDURE:

Sourcing and Storage of Coffee Grounds:

•  Initiate the process by obtaining used coffee grounds.
• Ideally, these should come from your recent brew sessions. If not, ensure they’ve been stored properly to limit exposure to air.
• Freshly used coffee grounds are optimal because prolonged exposure makes them more susceptible to contamination from competing organisms.

Blend Preparation:

• Utilize a large mixing tray or bowl.
• Gradually combine the coffee grounds with vermiculite, ensuring an even mixture. Vermiculite will assist in maintaining the moisture balance, which is essential for successful colonization.

Incorporation of Gypsum:

• If you’re opting to incorporate gypsum, this is the moment. Sprinkle it evenly across your blend, mixing it in thoroughly. Gypsum not only tweaks the pH balance but also contributes additional calcium and sulfur, essential minerals for mycelial growth.

Achieving Field Capacity:

• Field capacity refers to the moisture level where the substrate is damp but not waterlogged. You aim to have a mixture where, upon squeezing, only a few drops of water may be released. If it’s too wet, consider adding more vermiculite or coffee grounds. If too dry, sprinkle in more water and mix until you achieve the desired consistency.

Jar Filling:

• Filling: As you transfer the blend into your jars, be cautious about packing density. The substrate should be filled loosely, ensuring adequate air pockets and space for mycelial expansion
• PLEASE NOTE: If you followed our recipe (shown above) you shouldn’t have to worry about this however, ensure you leave about a 1-inch gap at the top to facilitate room for expansion and air exchange.
• Securing Lids: When placing the lid, ensure the rubber seal faces upward. This helps prevent the jars from getting vacuum-sealed during the sterilization process. Another option is to use a mycology lid such as one that contains a filtered vent and/or injection port (we have articles, DIY Supplies, and both Free & Paid for Mycology Courses hosted on our 🍄 Mushroom Academy!
• Foil Cover: Wrap the tops of the jars with aluminum foil. This provides an added layer of protection against potential moisture intrusion during pressure cooking.

Sterilization:

• Given the nutrient richness of coffee grounds, sterilization becomes pivotal. Load your jars into a pressure cooker, ensuring they’re elevated from its base. Maintain a pressure of 15 PSI for a duration of 90 minutes.
• If a pressure cooker isn’t an option, a steam bath for 2 hours can work, but be aware that this method is less efficient at eliminating potential contaminants.

Cooling Down:

• Post sterilization, patience is paramount. Wait until the jars reach room temperature. Introducing mycelium to a hot substrate can be detrimental to its health.