Coffee ground mushroom starter bin - oyster flush guide for apartment pantry shelves

To begin, gather your materials: a small plastic bin with a lid (like a 2-gallon shoebox size), oyster mushroom grain spawn, fresh used coffee grounds (no more than 24 hours old), and a spray bottle for water. For your bin, drill four to six small (1/4-inch) holes on all sides, including the lid, for air exchange. Stuff these holes loosely with poly-fil or a small piece of a clean sponge to allow air in but keep contaminants out. Collect enough fresh coffee grounds to fill your bin about three-quarters full. It's best to collect them from your daily brew and store them in a sealed container in the refrigerator for up to three days to prevent mold growth before you have enough.

Once you have sufficient grounds, it's time to prepare the substrate. Place the cool, used coffee grounds into your bin. There is no need for further pasteurization if the grounds are fresh from the brewer, as the brewing process itself pasteurizes them. Break up your oyster mushroom grain spawn with clean hands and add it to the coffee grounds. A good ratio is about one part spawn to four or five parts coffee grounds by volume. Mix thoroughly but gently, ensuring the spawn is evenly distributed throughout the grounds. The final mixture should be moist, like a wrung-out sponge, but not waterlogged. If your grounds seem dry, mist them lightly with water as you mix