Fresh Coffee Grounds Are Great Source of Minerals and NutrientsLooking to perk up your compost pile? Do you drink coffee? You might be holding the answer in your hands this very moment, or at least part of the answer. Coffee grounds have been used for many years by those “in the know” to boost the quality of their compost, making a superior soil amendment for free. The grounds are considered part of the “green” portion of the composting, speeding up the decomposition process while keeping temperatures high enough to kill off pathogens.
Coffee grounds provide energy in the form of nitrogen to the hard working bacteria doing all of the work in the compost. They also encourage beneficial microbe growth, contributing to a healthier soil. Another benefit is the minerals added to the compost such as phosphorus, potassium, magnesium and copper – all very necessary to the growing process. Earthworms absolutely love coffee grounds, preferring them to other food sources and turning them into highly prized vermicompost. For many years coffee grounds have been thought of as slightly acidic, but recent research shows that the grounds are usually pretty neutral in pH, but have a very high buffering capacity. This means that whether the soil is acidic or alkaline, the grounds will bring the pH back toward neutral, so they are good for any soil types. The moisture holding ability is very beneficial for loose soils, yet it acts to loosen heavy clay soils at the same time.
Some gardeners have worked the grounds directly into the soil, but it is best to add them to the compost pile and let decomposition release their nutrients first, then add the aged compost to the garden soil, working it into the top 2 – 3 inches in early spring and late fall. The grounds can make up to 25% by volume of the compost, and be used as a manure replacement for gardeners who don’t have ready access to those sources. Some city gardeners make their compost of leaves, cardboard and newspapers for the carbon side with coffee grounds and fresh grass clippings supplying the nitrogen to keep the pile going. It is best to let the compost decompose or age for at least 6 months, with a year time-frame yielding a higher quality amendment that looks very much like soil all by itself.