Now that gardening season is here, a great way to reuse your old coffee grounds is for a fertilizer as they make a great addition to the compost pile! They’re about 2% nitrogen by volume and serve as an excellent nitrogen source in compost, much like horse or cow manure does. Nitrogen stimulates root development, increases seed and fruit production, and promotes leaf growth.
Good homemade compost is made by mixing carbon-rich ingredients (dried leaves, straw, shredded newspaper) with nitrogen-rich ingredients (grass clippings, manures, coffee grounds, green plant trimmings). The fastest rate of decomposition occurs when there are 2-3 times the amount of carbon ingredients to nitrogen ingredients, so for every bucket of coffee grounds in the pile, you’ll want 2-3 buckets of dried leaves, etc. Maintaining this balance will also help reduce the odor of the compost; turning the pile regularly is also helpful. You can also add any unbleached coffee filters to the compost pile, but stay away from adding any white, bleached ones.
If you don’t have a compost pile where you live, you can still use the grounds in a garden. Just sprinkle small amounts around the soil surface or bury them in small trenches.