Waste Coffee Grounds Make For Great Shrooms

Coffee has never been so fashionable, from Hackney to Williamsburg we are inundated with bearded hipsters serving us up some fancy, new fangled coffee; the hilarity of this trend is quickly summarised by an article in the Huffington Post in which a hipster asks "can I get a double upside down mocha macchiato with soy -- low fat, no fat, no lid? Can you make it taste like Christmas too?"

Yet mocking the trend is not my aim, rather the important point is to draw our attention to the immense scale of our global coffee consumption. Many of us rely on that first cup of coffee to get us started in the morning, but do we ever stop to think about the coffee grounds left behind?

According to GroCycle, over 1.6 billion cups of coffee are drunk each day, with the UK responsible for about 80 million of these. In each cup of coffee only about one percent of the coffee biomass ends up in the cup, most of the grounds are leftover and go straight into landfill, adding to the amount of methane gas expelled into the atmosphere.

Thus, there is an incentive to find alternative uses for these waste coffee grounds and luckily this is exactly what people are doing. People are quickly discovering that there are endless possibilities: 

  • Re-worked is a company that produces a hybrid material from 60 percent coffee grounds, creating fashionable furniture with the new material
  • Starbucks is investing in a new lactic acid fermentation technique, which converts coffee grounds into feed for dairy cows
  • The engineer, Dan Belliveau, is creating 'coffee flour' from the cherry pulp of coffee. This flour is gluten free and rich in fibre, thus making a great addition to the healthy baking scene

However, today I want to focus on one particular way of reusing coffee grounds, one that is accessible to all and kills two birds with one stone - reducing waste and creating local food in urban environments.  This is the reusing of leftover coffee grounds to grow edible mushrooms.

It makes total sense. Normally, to grow mushrooms a crucial step is to sterilise the substrate, yet here this is already done by the pasteurisation of the coffee grounds that occurs during the brewing process. Thus, an energy intensive step is forgone.

So, let's look at who is doing what. The afore cited company, Grocycle, has created an urban mushroom farm in the heart of Exeter in a repurposed office building. They have also created grow-your-on-mushroom kits, distributing boxes of recycled coffee grounds mixed with oyster mushroom spores across the UK. Similarly, in the USA, two Berkeley graduates - Alex Velez and Nikhil Arora - have created a DIY mushroom kit; Wholefoods was their first customer with an initial sale of 3.14 pounds. Check out their stylish boxes:





Mushrooms: Cultivation, Nutritional Value, Medicinal Effect, and Environmental Impact - by Philip G Miles, Shu-Ting Chang