How To Compost Coffee Grounds: A Guide

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A cup of coffee is one of the most important parts of any day, especially first thing in the morning. 

However, there’s a lot of waste involved, with grounds only giving a lot of flavor on their first run through a coffee maker and being discarded afterward.

used coffee grounds in compost to build the soilPin

Unfortunately, this is true of fresh grounds and K-cups, and that’s a lot of money getting thrown out every day.

But what if we told you your used ground coffee was still quite useful and could provide plenty of nutrition for your garden once you’re done with them?

While it’s possible to use coffee grinds directly on some plants, the best way to recycle them is to add them to your compost.

Yes, even the K-cups can be emptied into the compost pile, although the plastic will need to be discarded.

How to Compost Coffee Grounds: A Guide

Composting used coffee grounds is safe and easy if you follow a few simple rules.

Why You Should Compost Coffee Grounds

Fresh coffee grounds are an organic material, meaning they decompose and leave behind nutrients.

The used grounds (ground up coffee beans) are chock full of nitrogen, one of the plants’ most important macronutrients.

In addition to nitrogen, it’s also an excellent source of several important trace minerals, such as calcium, magnesium, and potassium.

Even once broken down in the quality compost pile, the used coffee grounds help to improve soil structure.

Contrary to popular belief, used coffee grounds aren’t acidic but around 6.5 to 6.8 in pH, which means they can be safely used for just about every plant.

The carbon to nitrogen ratio is 20 to 1, allowing a compost pile with 25% percent coffee grounds to sustain internal temperatures of 140 to 160° degrees Fahrenheit for up to two weeks.

Used coffee grounds also deter garden pests while attracting beneficial nematodes, worms, and other composting helpers when sprinkled around the base of plants. 

In addition, composting coffee grounds are also good at improving water retention and drainage while reducing your carbon footprint.

Moreover, sprinkling used grounds around acid-loving plants like azaleas, blueberries, hydrangeas, and lilies give them an extra boost. It’s also excellent for use as a base for mulch around your vegetables and flowers.

Are Coffee Grounds Brown or Green?

This is actually a very important question you might not have thought about.

In composting, green refers to organic materials rich in nitrogen content, while brown refers to high-carbon materials. And in a compost heap, you need these two kinds of materials: green and brown.

Despite being a valuable source of carbon, the amount of nitrogen in used coffee grounds (approximately 1.45 to 2% percent nitrogen by volume) is enough to classify it as a green material.

And this can be confusing for many people, and you mustn’t accidentally include the grounds with your brown materials while preparing to start or add to a compost pile.

However, unbrewed o fresh coffee grounds are more acidic, between 6.5 to 6.8 pH. If you plan to use your unbrewed coffee grounds, make sure to use decaffeinated ones and play minimally to avoid problems.

Incidentally, used coffee filters are made of brown material and can be composted alongside the grounds they were used to filter.

Are Moldy Coffee Grounds Safe?

This depends largely on the type of mold.

Blue-green mold is perfectly safe for the compost pile, as is white mold.

Green mold is actually considered to be beneficial to compost and garden soil in general.

However, the grounds need to be discarded immediately if you see brown, black, or reddish-pink mold.

How to Compost Using Coffee Grounds

There are many ways to compost, all of which involve ground coffee.

One popular recipe is to mix ⅓ grass clippings, ⅓ leaves, and ⅓ used coffee grounds into the compost tumbler or traditional compost pile.

This is great for people with a lot of leaf and grass litter and contains a perfect blend of carbon and nitrogen.

Be sure to blend well and turn the garden compost as per usual.

You can use the also used kitchen waste or carbon-rich materials like shredded paper or straw in place of some of the leaves if you wish.

If you have paper coffee filters at home, you can shred them and add them to your coffee grounds and compost pile. This will provide a great green compost material.

For bokashi composting, simply add your coffee grounds every day or two (depending on how much you drink) and sprinkle it with bokashi bran just like you would any other food waste.

For vermicomposting, you’ll want to only add a small amount at first to the worm bins.

This will help acclimate the worms to the new material.

However, once you’ve introduced the grounds, you can add them as you would any other material, and the worms will love it.

You can also add the grounds to your existing compost pile and, as a soil amendment, work them like any other material.

Just be sure that the rounds make up no more than 25% percent of the total compost pile unless you use the 3-ingredient method we mentioned earlier.

Some Final Tips

Some anecdotal evidence suggests coffee grounds can help repel snails and slugs when sprinkled around a plant, although there is no hard evidence.

Moreover, keep in mind not to rely on used grounds as your only source of plant food, as there are possibilities of them suppressing the plant growth if applied too much.

Composting is a much better option because the grounds won’t release their nitrogen until they break down.

Additionally, you shouldn’t worry too much about getting more than 25% percent coffee grinds in your compost pile unless you have a small compost bin or run a coffee shop. Since that’s a LOT of coffee.

Also, if you want to increase the quantities of coffee grounds you’re adding to your garden soil but aren’t drinking enough coffee (or don’t like coffee for some strange reason), you can simply go to any local restaurant or local coffee house and request their used grounds.

Most places will gladly give you a good supply of coffee grounds for your garden, as it’s less waste for them to deal with.

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