Coffee has many uses, and spent coffee grounds can be reused for many things, even as a fuel. One of the easiest ways to recycle your coffee waste is to use it as a fertilizer. Since coffee is slightly acidic, make sure you fertilize with it only plants that love an acidic soil. Since caffeine is a mild insecticide, you’ll keep away the pests as well, if coffee is black.
Apparently, coffee is a great source of nitrogen and plants that enjoy more acidic soil can benefit from certain levels of nitrogen, like blueberries, azaleas and rhododendrons. According to The Spruce, if you plan on doing this, you’ll need to keep a close eye on your plant. If you’re “watering” it with coffee and the leaves of the plant start yellowing at the edges or turning brown, it may mean that the liquid coffee is adding too much acid to the soil. A solution to this could be watering down your coffee before you pour it onto your plant.
Another reminder: The coffee you water your plant with needs to be black. That may seem obvious, but pouring out your leftover brew that contains sweeteners or dairy could attract pests like gnats. Even if you’re just using black coffee, you should stick to doing this only once a week.
What’s left over in your coffee pot isn’t the only beneficial part of coffee for your plants — the leftover grounds can also benefit your growing green friends as compost or fertilizer.
Sprinkling grounds into your plant’s soil not only serves as a mild acid fertilizer, but it can prevent slugs from appearing and also keep pesky animals out, like cats or rabbits.
For those of you who enjoy a cup or two (or three or four) a day, this little hack could definitely help cut back your coffee waste.