There are several things you should avoid doing when brewing coffee. There is one thing, however, that’s perhaps the biggest mortal sin of making coffee — rebrewing grounds. However you make coffee, please never, never rebrew grounds. Here’s why grounds shouldn’t ever be rebrewed, and what you can do with used grounds instead.
Rebrewing Grounds Makes Dirty Water
If you don’t believe that rebrewing grounds results in a bad-tasting cup of liquid, perhaps you should just go ahead and try it. Put some old grounds you’ve already made coffee from in a coffee maker, add water and start brewing. We’re confident you’ll never do this again after you taste the resulting liquid.
We can’t bring ourselves to call what’s created by rebrewing grounds “coffee,” or even a “beverage,” because it doesn’t taste anything like coffee — or anything else that’s drinkable.
All the flavors in the coffee are weak, and the extraction rate will be messed up because the oils and other compounds that come out in the brewing process have largely been removed. There won’t even be much caffeine in the rebrewed concoction, eliminating any possible justification for drinking it.
Rebrewed coffee is essentially little more than dirty water. You might as well try some water from the dishwasher. It’ll probably look similar and won’t taste that different.
Repurpose Grounds in Other Ways
If you’re committed to reusing waste as much as possible, there are several things you can do with old coffee grounds. We recommend trying any or all of the following ideas.
First, used coffee grounds work well as fertilizers sometimes. They’re rich in nitrogen, which generally promotes leaf growth but not flower growth. Therefore, you probably want to avoid putting them on a flower bed. They can be great for green, leafy plants that need lots of nitrogen, though.
Second, old coffee grounds can serve as the main ingredient for coffee scrubs. There are many variations of coffee scrub recipes, but they usually are made from coffee, sugar, oil and (sometimes) essential oils. Dry, used coffee grounds work just fine for these scrubs. The coffee and sugar in these scrubs is exfoliating and can help get rid of dry skin, while the oils rehydrate and rejuvenate the skin.
Third, coffee grounds can be used as natural insect repellants. You might have luck infusing water with a lot of used coffee grounds, and then spraying the mixture to help prevent larvae from maturing into full-grown insects.
It’s more common, though, to use coffee grounds as you would a citronella candle. Dry out old grounds on an aluminum pan, and then use a little (just a little) lighter fluid to ignite the grounds. Once the lighter fluid burns out, the grounds should smolder — and their smoke has been shown to deter mosquitoes from coming into the area.
Finally, once coffee grounds have been used and reused, they can be added to a compost pile. Grounds can be added to a compost pile without too much concern about how they’ll affect the pile, for the organisms and worms that compost other foods generally are also happy to process coffee grounds. Additionally, coffee grounds won’t attract larger animals, like meats can.
Get Fresh Coffee to Make Coffee
Any of these four things are fine to do with old coffee grounds, just please never re-brew them. Instead, always use freshly roasted coffee when making a new pot or cup. For a constant supply of freshly roasted coffee, consider one of our coffee subscriptions.