Are you composting coffee grounds? Or using them in the vegetable garden? Used coffee grounds are a great way to improve your garden soil. And good soil = better harvest! Toss the remains of your morning cup of Joe in the compost!
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There’s often debate about the acidity of coffee grounds and how that might impact your garden soil, but Science Daily says:
Contrary to popular belief, coffee grounds are not acidic. After brewing, the grounds are close to pH neutral, between 6.5 and 6.8.
According to the article, used grounds are a high nitrogen material and can be added to the compost pile in lieu of manure. In fact, one interviewee claims that he had better success adding spent coffee grounds to his compost than with manure.
As long as you’re maintaining a fairly equal balance of carbon (straw, leaves) and nitrogen (coffee grounds, lawn clippings, kitchen waste) your compost pile will just keep on doing it’s thing. The Science Daily folks even say it’s okay to put used coffee grounds directly around plants, so long as you top the grounds with a layer of leaves or straw. It’s kind of like composting in place.
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Composting coffee grounds
I’ve always added my coffee grounds to the compost pile. In fact, one of my best garden beds is one that I topped off with gallons and gallons of this underutilized resource when my son was working at a local coffee shop. I just dumped the bucket of coffee grounds on top of the soil and let them sit for a month or so before planting out the garden bed, and it’s thriving.
Get in touch with your favorite coffee shop and ask if they’ll save their used coffee grounds for you. Or swing by Starbucks — they often have their used grounds all packaged up and ready for the taking. When adding coffee grounds to your compost, you can toss your paper filter in, too. Unbleached coffee filters are a good choice. Spent coffee grounds are also a great candidate for sheet mulching.
1. Worms love them
If you’ve made a worm composter (click for instructions), you can add your daily dregs to the bucket and the worms will quickly turn them into rich castings (aka, worm poop). The worms love the grounds — or at least they seem to! — and allowing the worms to process them transforms them into an entirely new product while giving the worms something to nosh.
2. Coffee grounds in the vegetable garden to add nutrients to the soil
In addition to composting coffee grounds, I’ve often tossed used coffee grounds in the vegetable garden around the plants. Sunset Magazine commissioned a study of Starbucks coffee grounds and found that not only are they a good nitrogen addition to compost,
use of the coffee grounds at the specified incorporation rates (rototilled into a 6- to 8-inch depth) will substantially improve availabilities of phosphorus, potassium, magnesium and copper and will probably negate the need for chemical sources of these plant essential elements.
3. Improved soil structure
That Sunset study also concluded that adding them directly to the soil can also improve the structure of soil. (Maybe that’s why my coffee ground garden bed is so happy?)
4. Composting coffee grounds helps sustain high temperatures in compost
An Oregon State University study found that a compost pile made up of 25% coffee grounds, the piles maintained a temperature of 135-155 degrees Fahrenheit for at least two weeks. This temperature is sufficient to kill weed seeds and pathogens that might be lingering in your compost pile. Another good reason to use coffee grounds in the vegetable garden!
5. Keep organic matter out of the landfill
Organic matter added to the landfill decomposes and produces methane, which is even more damaging to our environment than carbon dioxide. Diverting used coffee grounds to the garden reduces the amount of space used in the landfill and builds soil.
Originally published May 2011; this post has been updated.