Recycling Coffee Grounds: Using Coffee Grounds in your Garden and More ~ unl.edu

1. Recycling Coffee Grounds
With so many coffee houses around, there is interest in recycling used coffee grounds to divert them from the landfill. And being a plant product, home gardeners frequently question whether coffee grounds are useful for gardening.
Coffee grounds are a low-level source of nitrogen, having a fertilizer value of around 2.0 N, 0.3 P, 0.2 K, as well as a minor source of calcium and magnesium. Post-brewed coffee grounds are reported to be slightly to highly acidic, depending on the source, but no more so than peat moss. So, you could apply them to the soil for acid-loving plants, such as rhododendrons, azaleas and blueberries. They might even help keep your bigleaf hydrangeas blue. Or, you could spread them out over a larger garden area to minimize the pH effect. It's difficult to make a specific recommendation for an application rate, but it's always better to err on the lighter side, since the pH can be variable. A rate of 10 pounds (dry weight) per 1000 square feet would be conservative.
Composting is an excellent method to recycle the grounds. They have a carbon-to- nitrogen ratio of around 20:1. Use the grounds as you would green, leafy material, mixing with some dry, brown plant materials in the compost to achieve the ideal 30:1 ratio for composting. The Environmental Protection Agency suggests adding no more than 25 percent coffee grounds by volume. Vermicomposters can use coffee grounds but always mix the grounds with dry brown materials before adding them to the bin.
Because of the fine grind that is typically used for brewing, the grounds should not be used as mulch since they are likely to pack down tightly, decreasing aeration. Also avoid using coffee grounds with potted houseplants, because of the potential buildup of soluble salts.
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Source: Don Janssen, UNL Extension Educator.
Butler County Extension, 451 N 5th Street, Courthouse, David City NE 68632-1666 Phone: 402-367-7410 Email: butler-county@unl.edu Website: http://www.butler.unl.edu
Sarah Browning, UNL Extension Educator, can be contacted by phone at 441-7180: by mail at 444 Cherrycreek Road, Suite A, Lincoln, NE 68528: or by e-mail at sbrowning2@unl.edu.