8 Cool Reasons to Save Coffee Grounds That You Probably Don’t Know

Alexis @ Chemistry Cachet
by Alexis @ Chemistry Cachet

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If you are anything like me, each day you have leftover coffee grounds you toss in the trash. Now that I have Keurig, I always have a few pods a day full of coffee grounds.

I shared all my favorite coffees for Keurigs last week, and as you can see, I drink a lot of coffee. I always try to save my grounds though.

After reading this post, you will want to save all those leftover grounds too.

These super cold reasons to save coffee grounds are inspired by the chemistry that is sitting around the coffee waste.

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Cool Reasons to Save Leftover Coffee Grounds

First, let’s talk chemicals.

What Chemicals Are Found in Coffee Grounds

After a cup of coffee is brewed, there is an abundant amount of substances left in the grounds. Most research shows a high level of carbon and a small amount of Nitrogen. This article from Cornell about composting states it can be a 20:1 ratio of carbon to nitrogen.

You might be wondering why people say it is a good source of Nitrogen then?

Well, even though it has high levels of carbon, it also has a high Nitrogen content in comparison. So, it is the perfect combination of both.

When coffee is brewed, all the hydrophobic compounds are left behind in the grounds like oils, fatty acids, and cellulose. Also left behind are lignin, phenolics, and essential oils.

This chemical analysis from Food Bioprocess Technol shows the complete compounds in spent coffee.

Coffee grounds are typically acidic to begin with and the pH will rise overtime as it decomposes. New coffee grounds are only slightly acidic.

As you can imagine, all the chemical compounds in coffee grounds makes them pretty awesome for use in the garden. Not only are coffee grounds a great source of carbon and nitrogen, they also possess disease fighting properties like certain fungi and bacteria’s.

But, that isn’t all leftover coffee can be used for. There are many cool reasons to save your leftover coffee.

Use it for plant food.

Leftover coffee grounds not only help nourish the soil, but they feed plants too. If you have Chemistry Hacks for Home & Outdoors, you can use it for that awesome slow release plant food. Or you can use it like I do to feed roses.

Either way, small amounts on top of the soil of your plants every few weeks will give the plant some added nutrients.

Use it as an anti-fungal or anti-bacterial for soil.

Like mentioned above, coffee has been tested to fight fungal and bacterial disease that can plaque plants. Again, you can just put it right onto the soil to get these benefits.

Repel certain insects and ants.

This has multiple uses for the soil. Not only can it feed the plants, work as an anti-fungal/anti-bacterial, but it can also deter certain insects from your flour beds like ants and slugs. They are turned off by the chemicals and acidity. Always use fresh coffee grounds that have just been used since the pH does increase over a period of time as it decomposes.

Use it to exfoliate your hands.

With essential oils, fatty acids, and cellulose leftover in coffee grounds, this makes it great to exfoliate with. To exfoliate, set out your coffee grounds to dry, then use about a tablespoon of the grounds in your hand, rub around with some warm water, then rinse.

Make a sugar scrub.

Remember this coffee chocolate scrub? I make this all the time with coffee grounds! It smells so good and is great for all over your skin.

If you want to buy one, this is my absolute favorite! Smells so wonderful and works great!

Deodorize the air.

One of my favorite things to do with leftover coffee is to absorb bad odors in the air. It works really well for areas like the refrigerator or kitchen. I keep a bowl out and dump the grounds into it. It will work for a few days soaking up odor. If I have something that really smells bad in the kitchen, I will set out multiple bowls of coffee grounds.

Plus it just smells good on it’s own : )

Soak up grease on pans and pots.

Coffee grounds do such a good job of absorbing materials like greasy substances. One of my favorite ways to do this is after using a baking sheet to cook chicken in the oven. All that stuck on grease and chicken fat is lingering on the pan. I drain the fat to throw away, then sprinkle coffee grounds all over the pan. Scrub and rinse! It really helps clean, scrub, and absorb.

Use it as a stain.

Not only are coffee grounds beneficial, but they also have a nice dark brown color which will stain certain surfaces.

One way we have done this is staining paper to age it. I have some regular printer paper I printed out a label on. I added some water to coffee grounds, letting it sit for a few minutes until it was nice and brown. I just dipped the paper in there and let it dry. It looked brown and aged!

Use coffee stain for wood too.

Homemade Wood Stain With Leftover Coffee Grounds Recipe:

  • 1 cup coffee grounds
  • 1 cup boiling water
  • Coffee filter


  1. Take about 1 cup of coffee grounds and add about 1 cup of boiling water to it. Let it sit about 30-45 minutes, then strain it out with a coffee filter.
  2. On a piece of wood that you have sanded down, take a paint brush into the coffee and start brushing! I use thin even strokes over the surface.
  3. Let it soak in. Then repeat a few times.

This gives a very light brown color, but brings out all the natural lines in the wood.

Next time you make coffee, save your grounds to use for these serious cool tips! Coffee is a perfect example of how awesome chemistry is and makes your life better too : )

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Alexis @ Chemistry Cachet
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2 of 84 comments
  • Lct72175250 Lct72175250 on Jun 12, 2023

    I think you mean “hydroponic” instead of hydrophobic compounds! 🤪

  • William William on Oct 01, 2023

    I have read in another gardening site that coffee grounds as they deteriorate release a substance into the soil which is fatal for worms and to worms/and other beneficial insects.