Can You Compost Coffee Grounds? (Ways, Benefits & Other Uses)

‘Coffee’ – Just reading the word makes us feel alive, active, and grateful, all at once. Well, it’s understandable since coffee does have that effect on people! But has it ever crossed your mind what effect it has on our plants? Can you, in any way, treat your plants with this magical ingredient? Can you compost coffee grounds? Let’s dive in!

Yes, you can compost coffee grounds as they are an incredible source of Nitrogen, improve soil tilth and structure, and are excellent green compost material. It’s best to use around 20% by volume of coffee grounds in the compost pile, and make sure to add equivalent amounts of brown compost material.

Before you all get too excited to give your plants a taste of that wonderful drink, let’s understand what coffee grounds are.

What are Coffee Grounds?

Coffee grounds are the derivatives of the brewing process. Yes, that rich, timidly caramelized, subtly nutty aroma is because of them. After you relish each sip of that enchanting drink, the leftover dregs at the bottom of your cup are used coffee grounds, which are not so useless and can be advantageous for your plants.

Spent Coffee Grounds

How to Compost Coffee Grounds?

Coffee grounds can be composted in a compost bin, composting tumbler, or compost pile. However, it is essential to note that though coffee is brown color-wise, it falls in the category of green compost material. Therefore, adding equal amounts of brown materials to the compost is significant for the best results.

Here are the steps for composting fresh coffee grounds in a compost heap or bin:

  • Take a composting bin.
  • Add ⅓ dried leaves, dead plant clippings, hay, straws, coffee filter, etc., which are Carbon-rich brown items.
  • Add ⅓ of fresh grass clippings.
  • Add ⅓ fresh grounds, which are Nitrogen-rich green items, and cover the bin.
  • Turn the pile regularly to facilitate aeration.

And you’ll have your end-product, nutritious compost, in 4-6 months.

How to Compost Coffee Grounds in a Composting Tumbler?

Composting in Tumbler

Step 1. Add a layer of brown material

Add a layer of brown materials to the composting tumbler. Brown material can be anything like shredded paper, pine needles, twigs, straws, hay, etc. Brown materials are rich in Carbon and provide energy to the microbes. 

Step 2. Add a layer of green material

Add a layer of green to the composting tumbler. Green materials include grass clippings, kitchen scraps, tea bags, eggshells, and what we wish to compost – coffee grounds!

Step 3. Add some water

Sprinkle some water between the layers to facilitate composting and maintaining moisture content.

Step 4. Repeat the layers

Add layers of browns and greens alternatively., with the addition of water in between.

Step 5. Maintain the Bin

Keep a check on the moisture content and proper aeration in the compost pile for the best results.

NOTE: Turn the composting tumbler a few times and check once or twice weekly. There might be steam production, evidence that microorganisms are in action.

Follow these steps with the correct maintenance, and you will have your black gold ready in a couple of seasons.

How to Compost Coffee Grounds in a Bokashi Bin?

The Bokashi method is a very effective and less time-consuming method of composting spent coffee grounds. It is an anaerobic method of fermentation. All you have to do is:

Bokashi Bran for Bokashi Composting of coffee grounds
  • Add a layer of Bokashi bran to the drain plate at the base of the Bokashi bin.
  • Add coffee grounds and other food waste.
  • Add another layer of Bokashi bran.
  • Sprinkle coffee grounds on the bran and cover them with a lid. 

And that’s it! You can enjoy your coffee ground compost in just 4-6 weeks.

Quick Tip: Smell the compost. If the smell is foul, it is a sign that the green content is more in comparison to the brown. In this case, add more brown material to the compost.

Now you have your compost, but how do you know it is a good one?

Good compost will have:

  • Nice earthy smell
  • Temperature around 130° Fahrenheit
  • Crumbly structure

You have an idea about how to compost coffee grounds; it’s time to peer into the benefits of using this compost on your plants.

Benefits of Composting Coffee Grounds

1. Add Nitrogen

Coffee grounds are an excellent Nitrogen source, comprising almost 2% Nitrogen by volume. Adding coffee ground compost will encourage the growth of microorganisms in the soil.

NOTE: Coffee grounds are not Nitrogen fertilizers. For best results, it is advised to add Nitrogen fertilizer along with coffee grounds as the microorganisms in the soil consume the Nitrogen for growth and reproduction, and additional Nitrogen fertilizer will provide nutrients to plants.

2. Rich in Organic Matter

Coffee grounds add rich organic material to the compost, improving the characteristics and overall quality of the soil, ultimately supplementing plant growth.

3. Facilitates Aeration

Compost made up of coffee grounds creates tiny air pockets, which improve soil aeration.

4. Improves Drainage

Soil tilth and structure are improved by adding coffee grounds to the compost, and hence, better drainage.

5. Attract Earthworms

Like humans, coffee also attracts earthworms. According to Washington State University, earthworms have an insatiable appetite for coffee grounds, and adding coffee ground compost will enhance burrowing leading to increased aeration and water filtration.

6. Avoid Diseases

Compost having coffee grounds can help keep the plants free from soil-borne diseases such as fungal rots and wilts (Fusarium, Pythium, Sclerotinia) and bacterial pathogens (E. coli, Staphylococcus).

Slug on Plant Leaves

7. Repel Pests

Anecdotal evidence suggests that coffee grounds repel snails, slugs, rabbits, cats, beetles, aphids, and ants. So this compost might keep them away from your plants.

8. Keeps Weeds Away

Using coffee ground compost on soil inhibits weed growth and can help keep our plants clean.

9. Beneficial to the Environment

As most spent grounds end up in landfills, high anaerobic decomposition occurs due to insufficient oxygen. This produces high amounts of methane, which is 25 times more harmful than Carbon dioxide in contributing to global warming.

Therefore, it is better to compost the coffee grounds and make our plants and environment healthy and happy.

10. Add Phosphorus

According to North Carolina State University, coffee dregs have the ratio of N, P, and K as 2:0.3:0.2, which means adding them as compost to the soil will also help increase the phosphorus content responsible for building a robust root system.

11. Add Potassium

Potassium is an essential nutrient for the development of fruit. Adding coffee grounds to the soil will increase the potassium content, leading to more fruits.

12. Add Other Nutrients

Coffee grounds are also a good source of Magnesium, Copper, Calcium, Zinc, Manganese, and Iron, which will make the compost a good fit for soil.

So, your magical drink does more than you thought, right?

But remember, nothing in this world is perfect. Surprisingly, not even your coffee is. Everything has pros and cons. And using coffee for your plants has certain disadvantages too.

Disadvantages of Composting Coffee Grounds

  • A single coffee bean has 6 milligrams of caffeine, while one gram of used coffee grounds has approximately 4 to 8 milligrams of caffeine, which is a lot. If not fully composted, caffeine in coffee grounds will produce an allelopathic effect on plants, which may inhibit germination in certain seeds.
  • Composting coffee grounds will not increase soil acidity. Coffee grounds don’t make for acidic compost, and the pH can change over time. 

According to the University of Arizona, the pH of coffee grounds ranges from acidic to alkaline. It changes over time from 4.6 to 8.4, and it can be said that coffee grounds are not always acidic and are not necessarily used to lower soil pH.

Precautions While Composting Coffee Grounds

  • Make sure to use only 20% by volume of coffee grounds in a compost pile.
  • Allow coffee grounds to cool before adding to the compost pile as heat might kill the beneficial bacteria of the compost.
  • Avoid adding coffee grounds to the vermicompost bins as they can harm earthworms in confined areas.
  • Finally, don’t add an excessive amount of coffee grounds to the compost. 

But is composting coffee grounds the only way you can use them for plants?

Not at all. Though the best way is to compost coffee grounds, let’s dart at the other ways to use them.

Other Ways You Use Coffee Grounds For Plants

1. Apply directly to soil: You can spread the grounds and cultivate them into the soil.

2. Apply it as mulch: It is possible to apply coffee grounds as mulch; however, it is not recommended as coffee grounds are easily compacted due to the fine texture, resulting in the formation of a barrier to air movement and moisture.

The best way is to apply a thin layer of coffee grounds, less than 0.5 inches, as a mulch, followed by a thick layer, around 4 inches, of coarse organic matter, like wood chips.

3. Sprinkle on the soil: Sprinkling coffee grounds on the soil can help serve these benefits to the plants and avoid compaction, which seems to be a problem when applying them as mulch.

4. Coffee ground tea: You can make this beverage for your plants by adding 2 cups of coffee grounds with approximately 5 gallons of water. Let this concoction remain untouched for a few hours. And your coffee ground tea is ready! Use it in the liquid form or as a foliar spray.

NOTE: The best time to add coffee grounds to soil is just after the emergence of seedlings. However, coffee grounds can also be added in summers so that they have enough time to decompose before spring comes when it is planting time.

Nevertheless, it is best to try things on your own and have first-hand experience. So give your plants a treat once you finish that oh-so-amazing coffee!

Can we use flavored coffee for our plants?

Flavored coffee is good as long as its flavors are made of natural ingredients. It is not recommended to add coffee with artificial flavoring or high amounts of sugar.

Do coffee grounds kill earthworms?

No, coffee grounds do not kill earthworms. According to the University of Arizona, earthworms use coffee grounds as food and deposit them deep in the soil. This ultimately helps in improving the soil structure.

Can we pour hot coffee on plants?

No, you should not pour hot coffee on plants as it will lead to overheating roots.

How long does it take to decompose coffee grounds?

It takes around 3-6 months to compost spent coffee grounds in an outdoor pile with weekly turning.

Can we use coffee grounds compost for indoor plants?

Yes, you can use compost made from coffee grounds for indoor plants as it will provide various nutrients to your houseplants.

Where can we get coffee grounds if we don’t drink coffee?

You can have fresh coffee grounds from a nearby restaurant or coffee shop.

Are coffee filters compostable?

Yes, coffee filters are compostable. Adding them to the soil or compost pile is beneficial, as they are an excellent Carbon source. Use a shredded paper coffee filter or tear it into small pieces to ease decomposition.

Well, the best way to know about something is to try. So why don’t you grab a mug of coffee and say CHEERS to your newfound companion, plants? And don’t forget to compost the leftover coffee grounds. And if you use coffee filters and want to use them in your garden, hop on to our guide on can you compost coffee filters.

Using Coffee Grounds in the Garden – Cooperative Extension