Can I Put Coffee Grounds in My Composting Bin?

Every day you throw away used coffee grounds in the trash and may wonder if there is a better way of disposing of them, like composting. Wouldn’t it be great to be able to use your old grounds to help your garden and yard grow better?

So this begs the question; Are coffee grounds a good addition to your composting bin?

Coffee grounds are an excellent addition to any compost bin and add many great nutrients to your bin and soil. Because they are finely ground, they can easily break down at a fast rate. 

Let’s look a bit deeper into why coffee grounds are so great for composting and if other coffee-related materials can be composted as well.

Why Are Coffee Grounds Good For Composting?

Compost is designed by nature to release many nutrients slowly over time, making it highly beneficial to all sorts of plants. Although any pile of kitchen and yard waste will decompose over time, adding the right materials in the right proportions will speed up this process tremendously.

Coffee grounds are high in Nitrogen, so they are considered the green material in your compost bin. In addition to Nitrogen, they also contain potassium and phosphorus.

What I love about composting is that you’re taking material headed to the landfill and turning it into rich nutrient soil. Think of all the coffee grounds not only you throw away each day but all the used grounds from your local coffee shop. I knew someone who would pick up used coffee grounds from a nearby coffee shop and use them in their compost bin on a fairly massive scale.

Below, you’ll see a quick table reminding you what material is considered “green” and what is considered “brown.” Both are essential to the composting process.

Table comparing green and material used in composting. Green material is good for nitrogen and includes coffee grounds, vegetable and fruit peelings, and yard clippings.
Brown material is good for carbon and includes cardboard, sawdust, paper shredding's, and dried leaves and twigs.

How to Use Your Composted Grounds in Your Garden?

You may have your compost pile already started in a pile in the back of your yard or a composting bin. If you do, then great! You’re on your way to rich nutrient soil. If not, we’ll go through a quick and easy-to-follow tutorial on how to get started.

First, you want to decide where and how you wish to compost. I started by simply clearing a large area in the back of my yard. I like digging a wide shallow hole to start and then begin layering my green and brown material in it.

If you wish to keep your compost in a bin, you can either use an old trashcan or purchase a simple one from Amazon. A friend of mine uses this one and recommends it to people just starting out composting. It’s inexpensive, 220 gallons, and is designed with ventilation holes.

If you can spend a bit more money, around $100, I recommend an Outdoor Tumbling Composter Dual Rotating Batch Compost Bin. These tumblers take much of the work out of typical compositing and prevent wildlife from destroying your piles.

I also recommend purchasing a pitchfork for turning and aerating if you don’t already have one. Here is one I found on Amazon for a reasonable price.

Once you’ve decided how you are going to compost, go through the steps below to add your coffee grounds to the compost.

  1. Layer your coffee grounds (green material) with your brown material (dead leaves, shredded cardboard, sawdust). A good brown, green balance is the ratio of green and brown material necessary for good decomposition. Microbes do their best with a carbon to nitrogen ratio of 30:1.
  2. Spray a bit of water between layers to maintain good moisture levels in your compost bin.
  3. Once all your materials are layered in the bin, depending on what you use to compost will determine your next steps.
  4. IF USING A PILE or BIN: Thoroughly mix all material. If the pile is looking too dry, add more water. Add some brown material if the pile seems too wet and soggy.
  5. IF USING A TUMBLER: Close the lid and give a few spins. Let sit for a few days and spin again. Add more water if it starts to look dry.
  6. You can always add additional coffee grounds once the compost pile has started. Just be sure to add enough brown material to prevent soil that is too rich in Nitrogen.
  7. Continue to check and mix your compost bin every week until your compost materials are disintegrated, and you have nice earthly-smelling dirt.
  8. This process usually takes anywhere from three to six months.
  9. Sprinkle around your flowers, vegetable gardens, plants, and trees.
  10. Watch your flowers, vegetables, and plants grow!

TIP: Try to add equal amounts (in volume) of coffee grounds/green material and your brown material. But remember, once your compost pile begins the process of decomposing the material, you can be the judge and determine if you are low or high on either green or brown material.

Can You Put Too Much Coffee Grounds in a Compost Bin?

Yes, you can put too many coffee grounds in your compost bin. The result of too much coffee grounds is high levels of Nitrogen in your compost. These high levels cause the release of ammonium gas and create a foul odor.

In addition to high nitrogen levels, adding too many coffee grounds to your compost can decrease the number of earthworms in your pile or bin. These worms are very beneficial to your compost and can assist in the process.

To remedy high nitrogen levels, add some brown material, such as shredded cardboard, dead leaves, or sawdust. This will balance and dilute the strong chemicals in the grounds and lessen the effect on the worms.

Clues That Your Compost Needs More Brown Material (Carbon)

  • Overheating: The optimal temperature for a compost bin is between 135 and 160 degrees Fahrenheit. If it gets above 160 degrees, the organisms and bacteria needed in decomposition are not able to do their job; thus, leaving you with a pile that is doing nothing. In addition, if it heats up too much, your compost can catch fire! If you find your compost bin above this temp, turning or aerating will help release the heat. Then add some more brown material and water to the bin.
  • Smells of Rotten Egg or Sulfur: This is a byproduct of hydrogen sulfide due to insufficient air circulation and oxygen. To fix, aerate regularly and add some brown material like small sticks to help create air pockets.
  • Smells like Ammonia: Ammonia smells result from too much Nitrogen (coffee grounds or other green material). By adding additional brown material, you are adding extra carbon to balance out the excess Nitrogen. Continue to aerate and turn to help release the excess Nitrogen.
  • Slimy in Appearance: If your compost pile looks too wet and slimy, you need more carbon materials (brown materials).

How to Know if You Need More Green Material in Your Compost Bin

Now that we’ve discussed the problems that arise when your nitrogen levels are too high let’s look at when your carbon levels (brown material) are too high.

When your compost bin contains too much brown material and not enough green, you’ll notice the temperature inside the pile is not high enough for microbes and bacteria to do their work. Thus, creating an environment where decomposing cannot take place effectively.

Remember, your Nitrogen rich material, like coffee grounds, is what is going to increase the temperature of your pile. So, to counteract the abundance of carbon, you’ll need to add your nitrogen-rich materials.

Clues That Your Compost Needs More Green Material (Nitrogen)

  1. Pile temperature too low: As mentioned earlier, the optimal temperature for decomposing is 130 to 160 degrees Fahrenheit. The temperature is too low if your thermometer reads below this range and you don’t see some steam coming from your compost bin. Add some coffee grounds or other green material to the pile and mix.
  2. Material isn’t decomposing: The only reason to do a compost pile in the first place is to decompose kitchen and yard scraps to make nutrient-rich soil. So if the materials are not decomposing, there is definitely an issue. If, after a week, you don’t see any change in your pile, add some more green material to it.

Can Other Coffee Items be Added to Your Composting Bin?

Another coffee item that can be added to your composting bin is coffee filters. If you are going to add these to your bins, I recommend buying the unbleached filters. While many speculate that the bleach in the white filters dissipates by the time the compost is ready for use, some still worry it poses a threat.

So, I aire on the side of caution and use the unbleached filters.

Final Thoughts

To summarize, used coffee grounds are an excellent nitrogen source for your compost bin/pile. Ensure that your brown or carbon material is added in adequate proportions to prevent over or underheating and smells.

Now, get to composting!

For more great alternatives to using coffee grounds, check out our other article, “8 Things to do with Coffee Grounds.”

8 Things to do With Coffee Grounds

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