How to turn used coffee grounds into punchy kombucha – recipe | don't waste

"No problem," Mabel said, handing me a huge bag of used coffee grounds. "Last week, someone came to ask me to make vegetable leather out of it." I walked out smiling ear to ear, happy to be in touch with a local barista and to have just scored a pound of the best used coffee grounds from Browns of Brockley.

Around the world, almost 10 billion kilos of coffee beans are consumed each year, and these beans are grown on 10 million hectares across the so-called bean belt, an area about 25 degrees either side of the equator. Imagine the impact if the waste from all that coffee was reused to make food, fertilizers, leathers, skincare products, and even biofuel.

Coffee kombucha

I love recycling coffee grounds. For starters, they're free, and they're also carbon positive because you're reusing a product that would otherwise go to waste. Coffee kombucha is very similar to traditional kombucha and has a serious caffeine kick, so I tend to only have a small drink at a time, otherwise I can get coffee jitters or even get anxious.

I was pleased to learn recently that coffee consumption is associated with increased longevity and reduced risk of cardiovascular disease. If you're caffeine sensitive like me, don't worry because the other 100 or more biologically active components of coffee are likely to contain the health benefits. Also, this recipe will work great with caffeine-free coffee. Store your spent grounds in the freezer until you have enough (or ask for some at a local coffee shop). You will need a three liter jar, a clean kitchen towel and a rubber band or length of string.

Makes about 2 liters

30g unrefined sugar700g used coffee grounds300ml mature kombucha (homemade or store bought)1 kombucha scoby (ask a friend or buy it online)

Measure two liters of just - boil water in a heatproof glass or ceramic pot, add sugar and used coffee grounds and steep the night. The next day, strain the flavored water through a non-metallic strainer 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 place the jar in a warm place, about 20°C of direct sunlight.

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