How to Compost Coffee Grounds
Composting with coffee grounds is one of the best ways to make use of a waste product most of us just throw the trash! Epic Gardening Founder Kevin Espiritu explains all the ways you can compost with coffee grounds in your home and garden.
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Two of my passions in life are drinking coffee (lots of it) and being environmentally aware. Luckily, these two passions blend together perfectly in the garden. Or more specifically, in my compost tumbler.
We have one less reason to feel guilty about your coffee addiction! You’ll be glad to hear that there are lots of ways you can benefit your garden with coffee grounds. No need to give up your coffee habit just yet—your garden will thank you and you can save the grounds ending up in the landfill!
Hungry Bin Composter
The Hungry Bin Composter is:
- Fast and convenient
- Perfect for worm composting
- Highly efficient (up to 4.4 lbs of waste per day)
- Manufactured in New Zealand
Are Coffee Grounds Good for Compost?
Before you add coffee grounds to your compost pile, it’s important to understand the pros and cons.
Why should you add coffee grounds to your compost? Firstly, coffee grounds add organic matter to your soil. This improves your soil’s water retention, aeration, and drainage. Coffee grounds also encourage microorganisms that are beneficial to plant growth.
If you have a pest problem in your garden, coffee grounds have been shown to deter slugs and snails. It is unclear whether this is because they can’t tolerate the small amounts of caffeine, or whether they don’t like the coarse surface, or a combination of both.
There is also small amounts of evidence that used coffee grounds can help to deter ants and cats from your garden too, although there are better ways of deterring both.
To clear up some misconceptions, coffee grounds are not acidic. In the past, there have been concerns that as coffee is acidic, coffee grounds must also be acidic and therefore should only be added to acid-loving plants. However, studies have shown that the pH of coffee grounds is fairly neutral. The acid in coffee is water-soluble so the acidity mainly ends up in your cup of coffee.
But, used coffee grounds still contain small amounts of caffeine. Caffeine is not a great addition to your garden or your compost pile. However, the amounts are likely to be fairly low and will be diluted by the other items in your compost pile.
Where to Find Coffee Grounds For Compost
Don’t just stop with the coffee grounds produced in your own home. There are lots more sources of used coffee grounds, often free. Coffee shops and restaurants are a great source of free coffee grounds.
Starbucks is probably best known for this having introduced their Grounds for Your Garden program in 1995, offering free bags of used coffee grounds to their customers. But just ask in any coffee shop and they are often more than happy to give you their used coffee grounds.
Why not add a can near your office coffee machine and collect those too?
You can compost coffee grounds on any scale. So if you don’t have to have a large plot or a fully developed compost pile, don’t worry. You can compost coffee grounds in a container on your balcony or even donate to a friend, neighbor, or local community garden that could benefit from adding extra nutrients to their soil.
How to Compost Coffee Grounds
There are a number of ways to compost coffee grounds. Your preferred composting option will vary depending on the size of your garden, whether you have a developed compost pile, or whether you have another method of composting your green waste.
You may even find that your method will vary throughout the year depending on how active your compost pile is, how much plant coverage you have in your garden, and how much coffee you are drinking.
Here are a few methods you can try to make compost from coffee grounds.
Add Directly to Your Soil
This works well for smaller amounts of coffee grounds (like those produced from brewing coffee once a day). If you are producing larger quantities of coffee grounds or have coffee filters in your coffee grounds, I suggest using one of the other methods.
Sprinkle your coffee grounds onto the surface of your soil and mix well. Alternatively, add the coffee grounds to the surface and cover with leaves, compost, or mulch. Do not simply add the coffee grounds to the surface of your soil. If they are left as a layer on the surface, they can dry out and form a caked layer preventing water from penetrating your soil.
Note that coffee grounds are not a nitrogen fertilizer, despite having lots of nitrogen in them. Before nitrogen is released, the grounds need to decompose.
Coffee grounds will encourage the growth of microorganisms in the soil that use nitrogen to grow and reproduce. While the coffee grounds are decomposing into the soil, there may therefore be a slight reduction in nitrogen available to your plants. That’s why you may need to add a nitrogen fertilizer at the same time.
Add to Your Compost Pile Or Tumbler
If you are adding coffee grounds to your traditional compost pile or compost tumbler, treat them as green compost material. They are about 2% nitrogen by volume. The coffee grounds will need to be balanced with sufficient brown compost material such as leaves, or shredded paper.
I recommend adding equal parts leaves, grass clippings, and coffee grounds to your compost pile together. Mix the coffee grounds well and continue to tend your pile as usual, regularly turning and aerating to ensure it remains aerobic.
Limit your coffee grounds to no more than a third of the overall volume of your compost pile. This is not normally a problem, even for the most enthusiastic coffee drinkers among us!
Paper coffee filters will be easily broken down in your compost pile too, so feel free to throw those in at the same time. They provide a valuable source of carbon.
Add to Your Bokashi Composter
Bokashi composting provides a fast and easy way to compost all of your food scraps, including coffee grounds and filters. The bokashi process turns your coffee grounds (and other food scraps) into high-quality compost in just 4-6 weeks.
Simply add the coffee grounds to your bokashi kitchen composter every 1-2 days and sprinkle with bokashi bran. Treat the coffee grounds exactly the same way as the rest of your food waste.
Add to Your Worm Bin
Despite coffee grounds being unpopular with slugs, snails, ants, and cats, worms are very attracted to them. Freely add your coffee grounds and filters to your worm composter.
As with any new item in your worm bin, you may want to introduce them gradually so that your worms can become accustomed to them.
Key Takeaways
Composting coffee grounds is a great way to benefit your soil (and garden) and save them from ending up in a landfill.
Small quantities can be added directly to your soil. Larger quantities can be incorporated into your existing compost whether it’s a traditional compost pile, compost tumbler, bokashi composter, or worm bin.
No need to feel too guilty about your coffee habit… your garden will thank you!
Frequently Asked Questions
Are coffee grounds brown or green in compost?
Coffee grounds are considered greens in composting terms, meaning they are a nitrogen-rich organic material. When you’re composting coffee grounds, it’s important to balance them with browns, which are carbon-rich materials like dry leaves, straw, or shredded paper.
Can I compost coffee filters with coffee grounds?
Yes, you can compost coffee filters along with your coffee grounds. Most coffee filters are made from unbleached paper, which qualifies as a ‘brown’ carbon-rich material in composting. Make sure the coffee filters are free of synthetic materials and chemicals to ensure they break down efficiently.
Are coffee grounds bad for compost?
No, coffee grounds are not bad for compost. In fact, they are highly beneficial. Composting coffee grounds adds nitrogen to your compost pile, which aids in breaking down organic matter more effectively. However, it’s important to use them in moderation. Too many coffee grounds can make the compost overly acidic and compacted, hindering airflow and slowing down the decomposition process. To avoid this, mix coffee grounds thoroughly with other compost materials and maintain a balanced ratio of greens and browns.
Can I add coffee grounds to my worm composter?
Absolutely, you can add coffee grounds to your worm composter. Worms are fond of coffee grounds and will process them into rich vermicompost. When adding coffee grounds to your worm bin, sprinkle them in thin layers and mix them with other bedding materials.
How long does it take for coffee grounds to decompose?
Coffee grounds decompose relatively quickly, often breaking down in your compost pile within about four months. The exact decomposition time can vary based on factors like the compost pile’s size, the balance of greens and browns, moisture levels, and how often you turn the pile.
