Coffee Kombucha

My husband brought home a massive library book all about fermentation. The Noma Guide to Fermentation by Rene Redzepi and David Zilber is basically an encyclopedia in a single volume. If you're interested in fermenting stuff, you will find endless fascination in these pages.

I took a look at the various kinds of kombucha, and discovered something I'd never heard of before: coffee kombucha! I've been making kombucha for years. I always use black tea. I knew the bacteria in the mixture feed off the caffeine, as well as the sugar. So coffee kombucha makes sense, but this is completely new to me.

The best thing about this recipe is that it uses coffee grounds--the leftovers which would normally be tossed in the compost after brewing a cup of coffee. And if there's one thing we have TONS of in my household, it's coffee grounds! So right off the bat, the main ingredient in this recipe is basically FREE! What could be better?

Making coffee kombucha involves a little more time and effort than regular tea kombucha. Since this was my first batch, I read the instructions carefully and tried to measure precisely. I'm not really a detail-oriented person, so this was a challenge. But I managed to get 3 quarts of coffee kombucha into the pantry to ferment. The fermentation takes about 7-10 days, but our house is pretty darn cold at this time of year, so we may need to leave it a bit longer.

The bacteria in the kombucha eat the sugar and caffeine. The end product is slightly sweet, slightly sour, slightly fizzy, and totally delicious. To reap the benefits for the gut biome, and keep the bacteria alive and kicking, don't heat the kombucha over about 140F.

You can drink the coffee kombucha as is, or blend it into a fermented shake. I'll be sharing this recipe with you soon!

To Make Coffee Kombucha

Large, nonreactive sauce pan or pot
Large glass or ceramic fermentation vessel(s)
Active kombucha
SCOBY (Symbiotic Culture of Bacteria and Yeast)


240 grams white sugar
1.76 kilograms water
730 grams leftover, used coffee grounds (or 200 grams freshly ground coffee beans)
200 grams unpasteurized kombucha
1 SCOBY (I used one out of my constantly brewing batch of kombucha.)

Bring sugar and 240 grams of water to a boil in a large, nonreactive pot. Add coffee grounds to syrup and stir to combine. Add the remaining 1.52 kilograms of water. Let coffee mixture cool. Refrigerate overnight to infuse.

The following day, strain coffee mixture through a fine-mesh sieve lined with cheesecloth. Stir in the kombucha. Transfer SCOBY to liquid. Cover the fermentation vessel with a breathable cloth and rubber band. Set in warm place. (82 degrees is perfect, but a cooler temperature just means the fermentation process will take longer.) Leave to ferment for about 7-10 days. After 7 days, you might want to begin tasting. When you like the flavor and fizziness, decant kombucha into storage bottles and place in fridge. You can reuse SCOBY for your next batch of coffee kombucha.