Grounds for Concern: Weird and Wonderful Uses for Coffee Grounds

Coffee is the second most traded commodity in the world (after oil) and the second most popular drink in the world (after water). In the UK, sales have grown steadily by 10% per year and it’s a popular way for many busy workers to start their day.

One downside of coffee’s incredible popularity is the huge volumes of waste coffee grounds that are left behind – half a million tonnes per year in the UK alone – which are often sent to landfill. As the coffee grounds decompose in the airless conditions of landfill, they give off harmful greenhouse gasses.

However, just like your morning cup can help you rise to the challenges of the day, some innovative companies have risen to the challenge of reusing or recycling waste coffee grounds to give them a new lease of life. Have we been burying a valuable resource for so many years?

Feed for Mushrooms

Coffee grounds are rich in nutrients and therefore make an excellent food source for mushrooms. You can grow your own mushrooms in your own spent coffee grounds but it’s quite tricky and many amateur growers accidentally end up with nothing more than mouldy coffee grounds instead.

For an easier and more reliable introduction to mushroom growing, the not-for-profit enterprise GroCycle makes “grow-your-own” oyster mushroom kits. All you have to do is cut an opening in the bag of coffee grounds, soak it in water and keep the mushrooms moist as they grow.

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I’ve used a GroCycle kit and it’s great fun to watch the mushrooms grow from tiny dots to large clusters. The mushrooms are delicious and not at all coffee-flavoured. Despite being much more reliable than the DIY approach, the kits aren’t entirely foolproof as they can sometimes become infested with flies. If this happens, all is not lost and you can just compost the coffee grounds – flies and all.

Coffee as a Biofuel

Coffee grounds give off a lot of energy when burned, so they are a promising fuel source.

London start-up bio-bean collects waste grounds from instant coffee factories, offices and cafés across the country and converts them into more convenient pellets and “logs”, which are burned to heat buildings.

The factory can process up to 10% of the UK’s coffee ground waste. This reduces fossil fuel use (as the coffee logs are burnt instead) and as the amount of coffee grounds sent to landfill is less, methane emissions are also reduced.
As coffee grounds contain a lot of oil prior to being turned into solid fuel, bio-bean also hopes to develop bio-diesel in the future.

Turning Coffee into Ink

Domestic Stencilworks, a small screen printing studio in California, claims to be the only printer in the world to print designs on clothes using ink made from coffee grounds.

The grounds are mixed with vinegar and heated to form a thick, gloopy liquid – but having invested 4 years in discovering how to make the perfect durable ink, Domestic Stencilworks isn’t giving away all of the secrets of the process.

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3D Printing Coffee

Printing is no longer limited to two dimensions, and the range of materials that can be used to for 3D printing is quite astonishing, including glass, precious metals and even ice cream.

Now we can add coffee to the list of printable materials. 3Dom USA and c2renew worked together to devise a mixture of plastic and coffee grounds that can be used by many standard 3D printers. Alas, the material is not safe to use with hot liquids – so it would be unwise to use it to print a coffee cup, contrary to some suggestions in the media.

Turning Coffee Grounds into Coffee Cups

Those hoping for a coffee-based coffee cup may take heart from Kaffeeform’s initiative. The company gathers coffee grounds from cafés in Berlin, mixes them with wood particles and natural resins and moulds them into lightweight, washable, mildly coffee-scented cups and saucers. One cup and saucer set uses the grounds from six cups of espresso. This is the circular economy at its finest!

With so many ways of recycling coffee grounds there are fewer and fewer reasons to send them off to landfill. Perhaps as awareness of these alternative uses grows, cafés and entrepreneurs will create more value from this resource instead of letting it go to waste.