How to Grow Oyster Mushrooms with Beer and Coffee Waste


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How to Grow Oyster Mushrooms with Beer and Coffee Waste

We spoke to urban farmers building a fungal empire with beer and coffee waste.

As far as the mushrooms around me are concerned, we're standing in a forest.

Usually, these fungi are found deep in the woods, where they are free to poison, paralyze, and kill as many little worms as they please during their short but eventful lives.

But we're not in the forest. The oyster mushrooms and I are in an industrial building in the very urban neighbourhood of Hochelaga-Maisonneuve in Montreal.


Lysiane Roy Maheu inspects the spores. Photos by Nick Rose.

Walking among the tall white towers of fungus at Blanc de Gris are owners Dominique Lynch-Gauthier and Lysiane Roy Maheu, who work meticulously to recreate forest-like growing conditions for their oyster mushrooms—with a little assistance from coffee grounds and beer waste.

Here, mushrooms are grown year-round, nestled safely from Quebec's unforgiving cold and the prying hands of foraging chefs. But the absence of extreme weather and predatory chefs doesn't mean that there aren't other naturally occurring threats in the clean, sterile environment of Blanc de Gris.


"We have two main enemies—mold and flies. Mushrooms are basically mold, so the ideal growing conditions for them means a lot of other mould will be growing, too," says Lysiane Roy Maheu.

"With the flies, it's kind of like in Breaking Bad when he freaks out after seeing one fly in his meth lab and says, 'It's not a fly, it's contamination!' If we see a fly here, we freak out because they breed like crazy and nobody wants flies hovering around their food. We have to be really careful because the flies love our substrate."


Substrate is basically any substance that will allow mushrooms to grow, usually damp logs or trees in the forest. And choosing the appropriate substrate is an absolutely crucial step in mushroom cultivation. In fact, Blanc de Gris's name ("White of Gray") is an ode to the white stuff.

"In mycological jargon, the 'white' is substrate, which is any grain that will allow the growth of mycelium, which is the vegetative part of fungus. Gray is a reference to the city but also the caps of the pleurotes."


The first step in the urban mushroom-growing process is collecting coffee and beer remnants from local cafes and brewers. Next, that food waste is combined with wood chips from the City of Montreal, all of which is mixed and pasteurized at a high temperature.

What remains is substrate which is inoculated with mycelium and sent to incubation rooms where the mixture will sit for two weeks. From there, it's off to the greenhouses (which are more white and gray than green) where the spawn can "flourish," as Roy Maheu likes to say.


Quebec loves coffee more than any other province in Canada. Almost three quarters of adult Quebecers drink coffee and an estimated 6 million coffees are brewed on a daily basis in la belle province. Combine that with the fact that Montreal is home to a fledgling microbrewery movement, and you've got a lot of free substrate for Lynch-Gauthier and Roy Maheu's company.

Roy Maheu says she didn't really understand the craze surrounding mushrooms, or how chefs can become obsessed with foraging them, until she partnered up with childhood friend Lynch-Gauthier.


"Dominique loves mushrooms. She thinks they're beautiful and she's always talking about mushrooms. I never liked mushrooms until we started this project. For me it was more like, 'Is there a good business model here and a demand for this product?'"

Among the city's chefs, there is no shortage of demand for fresh, fleshy, year-round oyster mushrooms. "Chefs love it. When they see the mushroom, they're like, 'Wow! That's what a pleurotte is supposed to look like!' Most people aren't used to eating or cooking mushrooms that are this firm and meaty. Most of the time when they arrive at supermarkets, they're wet and limp."


Clients include local heavy-hitters Pastaga, Toqué!, and Les 400 Coups. "Blanc de Gris's oyster mushroom is a real jewel of urban farming," says Louis-Philippe Breton, chef and co-owner of Pastaga and a handful of other Little Italy shops and restaurants. "Their mushrooms are totally unique, have a beautiful bluish hue, and are always really fresh. We're really proud to be one of their clients."

Still, Lysiane Roy Maheu says that what attracted her to the project, above all, was its environmental impact.

"The environmental benefits are definitely the most important aspect for me—even more than the business side elements, and even the mushrooms themselves. The whole point is to use things that would otherwise go to waste to feed the city," Roy Maheu says, adding that if all goes according to plan, their facilities will be using 50 tonnes of organic material to grow 300 kilogrammes of coffee every week.


Given the grow-op-meets-Breaking-Bad vibe of the place, I can't help but wonder whether such facilities could be used to grow another kind of mushroom. Roy Maheu politely indulges my deviant line of questioning but reminds me that I'm here to write about food.

"Apparently, it's quite easy to grow magic mushrooms. It don't think that it would be difficult to grow them here but we really don't plan on trying anytime soon. I would probably be a lot richer if I did, but we're focusing on oyster mushrooms!"