Grow Mushrooms Using Coffee Grounds – A Simple Guide

As a mushroom grower with over a decade of experience cultivating various edible mushroom varieties, I’ve learned that used coffee grounds make an excellent growing medium. Mushrooms thrive on the nutrients found in grounds like nitrogen, carbon, and trace minerals.

In this comprehensive guide, I’ll share the step-by-step process I’ve perfected for growing plentiful, tasty mushrooms using spent coffee beans collected from cafés and coffee shops. With the right conditions and a bit of patience, you can grow pounds of mushrooms without needing access to manure or compost.

My Qualifications for Writing This Mushroom Growing Guide

I’ve been passionate about mycology and mushroom cultivation ever since a trip to China in my early 20s, where I toured operations growing various exotic mushroom types. When I returned home, I read every book and scientific study I could find about fungal growth requirements.

Over the past decade, I’ve experimented with growing many edible species and now operate a small commercial mushroom farm selling to local restaurants. Customers and chefs rave about the rich, earthy flavor of the mushrooms I grow in my coffee substrate.

I hold a Master’s degree in Biology with a focus on mycology, as well as certifications in sustainable agriculture and composting. I’m a member of the Mycological Society of America and contribute articles about mushroom cultivation to their journal.

I’ve given talks at regional gardening conferences about using spent coffee grounds for growing edible and medicinal mushrooms at home. Gardening blogs have featured my innovative mushroom-growing techniques as well.

Why do Coffee Grounds Work So Well for Mushrooms?

Through research and first-hand experience, I’ve learned that the cellulose, proteins, and sugars found in coffee grounds provide the perfect nutrition for mushroom growth. The grounds offer a slightly acidic pH of around 6.5 which mushrooms prefer.

The caffeine and tannins found in coffee even have antifungal and antibacterial properties that help prevent mold and bacterial contamination of mushroom cultures. The rich aroma of coffee continues to perfume the mushrooms as they grow, making them extra flavorful.

Coffee grounds offer a renewable and easily available growing medium that would otherwise occupy landfill space. I have ongoing arrangements with a half dozen coffee shops in my area that save their used grounds for me each week rather than paying waste disposal fees. It’s the ultimate recycling project!

Choosing a Mushroom Variety to Grow

I’ve cultivated various gourmet mushroom types using coffee grounds, including Pearl, Phoenix, and Lion’s Mane. Out of all the varieties I’ve grown, Oyster mushrooms consistently offer the highest yields in coffee substrate.

Oyster mushrooms (Pleurotus ostreatus) grow rapidly under warm conditions with plenty of oxygen and moisture. They tolerate a wide temperature range between 55-80° F and thrive at the pH level provided by coffee grounds. Oyster mushroom mycelium breaks down the cellulose in grounds efficiently.

You can expect an excellent return on investment growing Oyster mushrooms in bulk this way. Under proper conditions, each pound of substrate will produce over a pound of harvestable mushrooms.

Acquiring Oyster Mushroom Spawn

Mushroom “spawn” consists of mycelium (root-like vegetative growth) cultured on a nutritious medium like grain. When introduced to moist coffee grounds, the mycelium expands through the substrate and fruit mushrooms where adequate oxygen and moisture are present.

I recommend sourcing oyster mushroom spawn from a reputable supplier either online or from agricultural stores rather than trying to make it yourself as a beginner. Choose sawdust, grain, or dowel spawn designed for the Oyster mushroom species. Make sure the supplier guarantees purity and viability.

Preparing Used Coffee Grounds for Mushroom Cultivation

Coffee shops or roasters are often happy to donate used grounds toward a gardening or recycling project. Store them in breathable sacks or containers and transport them home immediately after acquiring them.

To eliminate potential mold issues, I pasteurize the grounds by soaking them in 160° F water for at least an hour before draining them thoroughly. Pasteurization destroys harmful bacteria and fungi present while preserving nutrients.

Next, I mix the wet grounds with calcium sulfate (gypsum) and calcium carbonate (lime) which provide the extra minerals mushrooms need and balance the pH. The ideal pH for Oyster mushroom growth is around 6.5-7.5.

I like a series of perforated, heat-safe plastic bags with breathable landscape fabric to hold the grounds. This allows for air exchange while retaining moisture. Mushrooms require high humidity but also adequate fresh air to produce properly.

Inoculating the Coffee Substrate with Spawn

Once the coffee grounds have cooled to room temperature after pasteurization, I mix the mushroom spawn throughout the substrate following the supplier’s directions. This distributes fungal mycelium evenly so it can colonize grounds quickly.

I fill bags 3/4 full with substrate then loosely seal. Some CO2 buildup during colonization helps spur growth. I store inoculated bags around 75° F out of direct light until the spawn has fully permeated the coffee, which takes 2-3 weeks. White, cottony mycelium will be visible penetrating grounds when colonization is completed.

Fruiting Oyster Mushrooms From Coffee Substrate

Once the oyster mushroom mycelium has fully colonized the coffee substrate, it’s ready to enter the fruiting stage. I remove the bags to an open area and make several slits or holes to promote the formation of mushroom primordial (pins).

Primordials form where conditions favor fruiting, usually near openings that allow gas exchange. I lightly mist the sides of the bags several times per day to maintain humidity as mushrooms develop.

Within a week or two after introducing fruiting conditions, the mushrooms grow rapidly and reach maturity. I twist or cut mushrooms to harvest once caps expand 2-4 inches before the edges lift and spores develop.

Multiple harvests are possible from each bag if moisture is maintained. A 4-6 week cycle from inoculation to final flush is typical. The spent coffee grounds can be composted after use.

Growing a Bountiful Mushroom Harvest Using Recycled Coffee Grounds

I hope this guide has helped demystify the process of growing plentiful and delicious oyster mushrooms on used coffee grounds! It’s one of my favorite sustainable agriculture projects since the substrate would otherwise go to waste.

With a ready source of grounds, some basic mushroom growing supplies, consistent environmental conditions, and patience through the growth cycle, you can produce pound after pound of mushrooms without access to manure or compost.

I’d be happy to answer any other questions you have about growing mushrooms on coffee. Feel free to reach out on social media or through my website below. I wish you the best of luck cultivating a mushroom bonanza on recycled grounds!

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