If only the world’s annual 10bn kilos of used coffee grounds were used for fertiliser, leathers, skin-care products and even bio-fuel. Or this addictive kombucha …

How to turn spent coffee grounds into a punchy kombucha – recipe

o problem,” Mabel said as she handed me a huge bag of used coffee grounds. “Last week, someone came in asking me for some to make a plant-based leather.” I walked out grinning from ear to ear, happy to connect with a local barista and to have just scored a kilo of Browns of Brockley’s finest used coffee grounds.

Across the world, almost 10bn kilos of coffee beans are consumed each year, and those beans are grown on 10m hectares across the so-called bean belt, an area roughly 25 degrees on either side of the equator. Imagine the impact if the waste from all that coffee were repurposed to make food stuffs, fertiliser, leathers, skin-care products and even biofuel.

Coffee kombucha

I love upcycling coffee grounds. For starters, they are free, and they are also carbon-positive, because you’re repurposing a product that would otherwise have gone to waste. Coffee kombucha is much like traditional kombucha, and has a serious caffeine kick, so I tend to have only a small glass at a time, otherwise I can get the coffee jitters or even anxious.

I was happy to learn recently that coffee drinking is associated with increased longevity and a reduced risk of cardiovascular disease. If you’re sensitive to caffeine as I am, don’t worry, because it’s likely that the other 100 or more biologically active components in coffee contain the health benefits. Also, this recipe will work just fine using caffeine-free coffee, too. Keep your spent grounds in the freezer until you have enough (or ask for some at a local coffee shop). You will need a three-litre jar, a clean tea towel and a rubber band or length of string.

Makes About 2 litres

30g unrefined sugar
700g used coffee grounds
300ml mature kombucha 
(homemade or shop-bought)
1 kombucha scoby
 (ask a friend or buy it online)

Measure two litres of just-boiled water into a heatproof glass or ceramic jug, stir in the sugar and spent coffee grounds, and leave to infuse overnight. The next day, strain the flavoured water through a non-metallic sieve into a fermentation jar, add the kombucha and gently float the scoby on top. Cover the jar with a clean tea towel, secure it in place with a rubber band or string, then put the jar in a warm, roughly 20C spot out of direct sunlight.

After a few days, start tasting the kombucha – depending on the ambient temperature, it will take between three and 14 days to ferment. Strain into sterilised bottles, keeping back 300ml of backslop for the next batch, and store in the fridge, or leave to ferment a second time, which will carbonate the drink.

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