Used Coffee Grounds (UCG) have been used on plants and in compost for hundreds of years.
Somewhere along the way most of us gave it away, stopped growing our own food, and relied on an increasingly effective industrialised effort to provide food to the table.
Most of us are totally dependant on food production systems which exclude us from all but the final step of consumption – We buy and consume only the end products, and if for whatever reason the shelves become empty, the only thing left to do is starve.
I wanted some measure of control over how my food is produced, while appreciating the environmental footprint of doing it.
The first step was to start improving the quality of my soil through compost, fertilizer, and vermicast. This is when I discovered an almost limitless and cost free additive to all three of those crucial soil amendments – Used Coffee Grounds.
Since March 2010, I have collected over 2 tonnes of used coffee grounds, and it has all been used in my compost bin, dug into raised garden beds, around the base of fruit trees, liberally sprinkled over the lawn, or handed out to family and neighbours.
Unless you had heard of, or used coffee grounds in your garden, you might think it all weird. As we go through some of the environmental benefits and physical properties of the material, it quickly makes sense why more of us should be making use of it. As the hundreds of YouTube videos attest to, this knowledge is enjoying a digital age revival.
Reducing Landfill by Using Coffee Grounds
Approximately 20 grams of coffee grounds remains every time an espresso machine is used, which is then typically thrown into the bin, and ends up in landfill.
20 grams might not seem like a big amount, until you consider that 5000 lattes work out to about 100 kilos of used grounds, 50,000 lattes work out to about 1 tonne.
Think about the millions of people who stop into cafes or use an espresso machine at home at least once a day. All those tens of millions of drinks make for many tonnes of landfill each and every day.
Given there is so much of the stuff being generated, availability is not an issue.
Most cafe owners would be more than happy to put some coffee grounds aside for you if you ask.
One chain that actively provides this service is Starbucks, who have an initiative known as ‘Grounds for your Garden’, and if you have been in their stores over the past five years may have noticed a stack of 2 kilo bags sitting in a basket at the front of the counter.
Another way to get supply, and one of the things I do, is to arrange to collect coffee grounds generated at work.
My building has at least 5 espresso machines which are emptied daily, and all the used grounds are left for me in a room in the basement car park.
It took a couple of tries to get the process working, but now I’m collecting around 100 Kilos per week, thanks to all my colleagues and their love of coffee.
What is in Coffee Grounds?
There will always be variation with a natural product, and the specific contents of coffee grounds can change slightly depending on the origin of the beans, how they were roasted, ground, and used in the espresso machine (including the water that was used). These are however what you would typically expect.
Nitrogen is an abundant element in our atmosphere and when converted to a solid form is readily used by plants. Coffee grounds have a carbon to nitrogen ratio of 20 – 24:1, which is about the same as grass clippings.
The relatively high nitrogen content makes coffee grounds a ‘green’ addition to the compost bin, and a great offset against high carbon ‘brown’ additions such as leaves (60:1), straw (75:1), and cardboard (350:1).
Much of the nitrogen within coffee grounds is of a type that must first break down in the soil before the plants are able to make use of it, which makes the grounds just like a slow release fertiliser when put directly into the soil, providing ongoing nitrogen input into the garden.
Used coffee grounds (UCG) are slightly acidic, with a range typically between 6.9pH and 6.2pH.
It would be higher except that most of the acid within the beans is extracted during brewing.
For many vegetable and ornamental plants, the desirable pH range is 6.9 to 5.8. A pH level of 7.0 is considered neutral, and from there it is increasing in alkalinity.
Coffee grounds contain phosphorus and potassium (which with Nitrogen completes the macronutrients required for all plant growth), and includes magnesium (a secondary nutrient) and copper (a micronutrient), in sufficient quantities that you will not need to get these from other sources.
Coffee Grounds impact on animal life
In learning about organic gardening, I have come across a large number of traditional methods for controlling garden pests.
If for example, I make a solution of soap, garlic, chilli, and water to deter aphids, then that’s one less bottle of chemical poison in the environment.
Coffee grounds have long been used in gardens because of their impact in controlling pests.
When applied to the soil of your garden, coffee grounds will deter snails and slugs, which are affected by even trace elements of caffeine, but more so because they don’t like travelling over the course grounds.
I have seen a dramatic reduction in snails and slugs since using coffee grounds in the soil. If you have them in plague proportions and the above is not effective, you might want to try fresh coffee grounds, before the caffeine has been extracted.
I have seen a similar reduction with ants, and although not as troublesome as snails and slugs, they can prove damaging to seeds and seedlings when in large numbers.
Having a layer of coffee grounds acts as a barrier that ants will not readily cross, and while the effects are not as long lasting as the chemical ant barriers, they do not contain all the poisons either, and it is no trouble putting down more grounds once the first lot has broken down.
Although I have never had a problem with cats in the garden, there is some evidence to suggest that they do not like the smell of coffee grounds and will prefer to keep away from it.
One creature that does love coffee grounds is perhaps the most beneficial to the garden, these being earthworms.
From my own experience and from many others, they love the stuff, are attracted to it, and your soil will be healthier as a result.
This applies just as much to the worm farm as it does to applying it directly into the garden. Worms of all types will be more productive as a result.
Preparing your own garden soil
A gardener once told me that he didn’t feed plants, he fed the soil which feeds the plants.
As long as you have good quality soil, you will have more healthy and productive plants. In addition to the result it brings to the garden, there is a great deal of satisfaction in returning a good percentage of our ‘garbage’ back into the earth.
When added to your compost bin or heap, coffee grounds will raise those internal temperatures, which speeds up decomposition, and the end result will be beautiful, black, rich compost.
The most common ingredients I use for compost now are kitchen scraps (no meat or pineapple and limited citrus), shredded cardboard and paper, coffee grounds, leaves and twigs, and any edible plants no longer being productive.
I would recommend limiting the use of coffee grounds in the worm farm or compost bin to about 25% of the total volume. The reason being is that you need a balance of ingredients with most recipes, and this is no different.
If you would rather use ground coffee as fertilizer in liquid form, add half a kilo of coffee grounds into a bucket with 10 litres or so of water, let the mixture warm up to ambient temperature, swish it all around and then apply directly onto your plants.
I have heard that this works particularly well with roses, camellias, azaleas, gardenias, hydrangeas, rhododendrons, and blueberries.
There is one final benefit; your garden will carry the aroma of freshly prepared coffee for sometime after being applied!
Ground to Ground and how you can get involved!
For the Cafe or Coffee House
For Cafes wanting to reduce their contribution to landfill, and demonstrate to customers your environmental commitment, you will find the article ‘How a cafe turns coffee grounds to compost‘ a good place to start. When you feel ready to give it a try, we can add you to the map below, so everyone will know about it.
You are also welcome to print out copies of the Ground to Ground Brochure to give to your customers. It is an easy way of letting them know the benefits of coffee grounds, which makes giving them out easy.
For anyone Working in an Office
If you have an espresso machine at the home or office then you have everything you need to start using spent coffee grounds. You will find the Collecting Coffee Grounds from the Office series of articles outline all the steps you need to take.
To join the many volunteers and cafes that are involved in the Ground to Ground initiative, please contact us at firstname.lastname@example.org. Always happy to help out in anyway we can.
If you are looking to make use of coffee grounds for your own garden, you have come to the right place. There is a whole series of articles on used coffee grounds and how they will benefit your garden.
This link for the collection of articles for Ground to Ground, is where you will find a growing body of information on the collection and use of coffee grounds, and already the most comprehensive available on the web.
What are some of the things that you are doing (or planning) to make a difference?
- London Ground to Ground – 2 Months into the Campaign! (groundtoground.org)
- Coffee Grounds with Austin Ground to Ground (groundtoground.org)
- Survey – Want to Collect Coffee Grounds But Can’t Because… (groundtoground.org)