Beyond Coffee has put together the Growkit that allows people to reuse their coffee grounds to grow edible mushrooms in a small bucket in just four weeks.

Only 0.2% of nutrition from coffee beans is utilised when making coffee. Once the aroma has been infused in the water, the remaining 99.8% ends up in the bin. Beyond Coffee has found a way, as the name suggests, to take advantage of the remaining grounds by designing a GrowKit for people to grow edible oyster mushrooms in coffee grounds.

To grow the mushrooms, a small amount of cooled coffee grounds must be mixed with a bag of mycelium – the vegetative part of a fungus – and left in a dark location for a couple of days. After a white mass of mycelium covers the surface of the grounds, more can be added repeatedly over the course of three weeks or until the bucket is full, kickstarting the fruiting phase. The bucket is moved to a lighter, colder and more humid location. After approximately one week, the first oyster mushrooms begin to make their way through small holes covered by tape, and a few days later the first round of oyster mushrooms should be ready for harvest.

Mushroom lovers who lack patience can also purchase all they need for a fungi feast. In their store, Beyond Coffee sells fully grown and harvested mushrooms, grown on grounds collected from local restaurants. To ensure nothing goes to waste, the mushroom substrate from the production is upcycled by an organic farmer who uses it as soil fertiliser.

The GrowKit is a cheap source of mushrooms for households that can help to reduce food waste. Each batch of coffee grounds can produce mushrooms approximately three times – a total of 0.5 kilograms, and can be reused multiple times by closing the holes with new tape, emptying 80 percent of the substrate and adding new coffee grounds. If the substrate is contaminated by mould or is too dry, it can be restarted by adding new ground coffee and a bag of mycelium.