Compost Your Coffee Grounds

Next time you order a latte at your favorite coffee shop, ask if they save the grounds from all the coffee they brew. Coffee grounds are an excellent addition to the compost bin.

When I go to my local coffee shop, I often come out with more than a cup of coffee. Near the door, they have a bin with free bags of used coffee grounds. Like most avid gardeners, I find it impossible to resist free food for my garden!

In the spring, I spread handfuls of coffee grounds around my acid-loving plants—azaleas, blueberries, rhododendrons. The grounds are slightly acidic and besides helping to lower the soil pH, they foster the humus-rich soil texture these plants really love.

In late summer and fall, I dig coffee grounds right into the vegetable garden after removing early-season crops such as peas and spinach. In the winter, I add the grounds to my compost pile. They’re a good source of nitrogen at a time of year when that can be a little difficult to come by.

Efficient composting depends upon a well-balanced mix of ingredients, which generally fall into two categories: browns (high carbon), and greens (high nitrogen). The list at right gives examples of both types of ingredients. The ideal ratio is 25:1 (brown to green) but most people find three parts brown and one part green works quite well. Remember to layer your ingredients, keep the pile moist (like a well-wrung sponge) and turn it occasionally to incorporate a fresh supply of oxygen for the microbes.

• Master Composter, a website for composting enthusiasts, conducted a Coffee Grounds Survey on the use of grounds—in compost and in the garden.
• If you're looking for a source of grounds, try Starbucks Coffee and Peet's Coffee. Both companies have researched the issue further and share the results on their web sites.