Grounds, which Parisian brasseries throw out daily by the tonne, are perfect for the job, and a snapshot of a fast-growing urban agricultural trend.
The mulch of grounds is mixed with cardboard and wood chips and shoved into lengths of plastic with pieces of mushroom culture.
They are then hung vertically in a dark space and left to incubate for a fortnight.
“We are reproducing undergrowth subsoil conditions. The temperature and humidity are comparable,” explains Arnaud Ulrich, co-founder of UpCycle-La boite à champignons (mushroom box), based in the Paris suburb of Saint-Nom-la-Breteche.
Nestled away from the light, the spores of mushroom mycelium fungus — a key food source for many soil invertebrates and which can also help to clean polluted soil — rapidly spread as they would beneath the roots of a tree.
After incubation, the bags containing the grounds and spores, by now completely white, are transferred to a different room for “fructification”.
There, the lights are switched on and humidity reduced. Cuts are made in the bags, allowing the mushrooms to emerge.
“The mushrooms are ‘stressed’ — which makes them want to reproduce and free up their spores, leave the bags,” says Ulrich. “It simply remains to harvest them.”
Ulrich says urban agriculture is first and foremost about recycling organic waste from cities as a means of expanding the move towards a regenerative, ‘circular economy’ making more judicious use of finite resources.
“Thirty percent of urban waste is useful biowaste and today, only five percent of this organic matter is recycled,” he notes.
Published in Today’s Muslim, February 25th 2019.