Used coffee grounds are an excellent (and free!) substrate for growing certain types of mushrooms — especially oyster mushrooms (Pleurotus spp.). Here’s how you can do it step-by-step:

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🌱 Why Coffee Grounds Work

Coffee grounds are:

• Rich in nitrogen and other nutrients
• Pasteurized (because brewing sterilizes them)
• Fine-textured and easy for mushroom mycelium to colonize

But — they’re also prone to contamination, so cleanliness is crucial.

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🍄 Materials You’ll Need

• Fresh coffee grounds (preferably used within 24 hours)
• Mushroom spawn (oyster mushrooms are best for beginners)
• Clean container or grow bag (with small air holes)
• Optional: straw or sawdust to mix with coffee (improves texture and aeration)
• Spray bottle for misting
• Dark, humid place for incubation

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🔬 Step-by-Step Process

1. Collect Coffee Grounds

• Use grounds the same day they’re brewed (avoid moldy or dried-out ones).
• If collecting from a café, store them in a clean, airtight bag or container.

2. Mix the Substrate

• Combine coffee grounds (80%) with mushroom spawn (20%) by weight.
• Optional: Mix in some pasteurized straw or sawdust (up to 50%) to prevent compaction.

3. Fill the Container

• Place the mix into your grow bag or plastic bucket with small air holes (about 2–4 mm).
• Press lightly, don’t compact too much.

4. Incubate

• Keep in a dark, warm place (20–25 °C / 68–77 °F) for 2–3 weeks.
• You’ll see white mycelium spreading through the substrate.

5. Fruiting

• Once fully colonized (white throughout), move it to a cooler, brighter place with high humidity (85–95%).
• Cut small holes or open the bag to expose the mycelium to air.
• Mist 2–3 times a day.

6. Harvest

• Mushrooms will start to form in 7–10 days.
• Harvest when the caps flatten out.
• You can usually get 2–3 flushes from the same substrate if kept moist.

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🌍 Tips

• Use coffee from local cafés (many are happy to give it away).
• Compost the spent substrate after the final flush.
• Mix with other organic waste for improved yields.