Reusing coffee grounds: practical tips to reduce waste

What to do with coffee grounds after brewing?

Once your coffee is brewed, the grounds aren't necessarily trash. You can compost them, use them in moderation in the garden, use them for certain household chores, or even repurpose them for creative activities.

The important rule is simple: not all uses of coffee grounds are equal. Some tips circulate widely on the internet, but they are exaggerated, misunderstood, or only suitable for certain situations.

For example, coffee grounds are neither a complete fertilizer nor a universal pest repellent. And because they still contain caffeine residues after brewing, it's also best to keep them out of reach of animals.

At KOOTA, the idea is less about turning every spoonful of grounds into a miracle product and more about finding a second life for them when it's genuinely useful.

And if you've arrived here before even choosing your next cup, you can find all our products. For the grounds, we'll take care of the rest.

First, properly prepare your grounds

Before thinking about what you're going to do with them, check their condition. Grounds that have just come out of a coffee maker, filter, or portafilter still contain a lot of moisture.

This moisture isn't an issue if you add them immediately to compost. However, it becomes less practical if you want to store the grounds for several days for DIY, cleaning, or other household uses.

For compost, use them directly

You can place the still-damp grounds in your composter with other organic materials. They should simply remain one ingredient among others.

The goal is not to create an entire layer of coffee. As with any balanced compost, you need to alternate materials and avoid excessive concentrations of a single waste product.

For other uses, dry them

If you want to store your grounds, spread them in a thin layer in a clean container or on a suitable surface, then allow the moisture to evaporate.

Avoid enclosing very damp grounds in a closed container for several days. Mold can appear during storage.

Once dry, they become much easier to measure and use. This is particularly useful if you want to keep them for a creative activity or occasional household use.

You can also adapt your coffee preparation method to produce less waste around the cup. A reusable coffee accessory, when it matches your extraction method, can contribute to this logic.

In the garden, mainly put the grounds in the compost

This is probably the most well-known use. It's also the one that deserves the most nuance.

Coffee grounds contain nitrogen as well as small amounts of potassium, phosphorus, calcium, magnesium, and other micronutrients. But this is not enough to make them a complete fertilizer capable of meeting your plants' needs on their own.

After brewing, their pH is generally around 6.5 to 6.8. In other words, used coffee grounds are not acidic enough to permanently change the pH of soil.

The idea that acid-loving plants should systematically be surrounded by grounds is therefore far too simplistic.

Add them to a diversified compost

Compost remains one of the simplest solutions for regularly valorizing your grounds.

However, the Oregon State University Extension recommends not exceeding approximately 20% grounds in the total volume of compost. Too high a proportion can become unfavorable to plants.

The principle is therefore easy to remember: grounds, yes; compost made mainly of grounds, no.

Combine them especially with leaves, plant waste, and other compostable materials. Once decomposed with the rest of the compost, they contribute to the production of more homogeneous organic matter.

Can coffee grounds be put directly on the soil?

Yes, but sparingly.

A small amount incorporated into the soil is not the same as several centimeters of grounds regularly spread around a plant.

Used in excess directly in the soil, the grounds can temporarily immobilize some of the available nitrogen during their decomposition. Caffeine residues can also affect the germination or development of some young plants.

If your goal is simply to nourish your garden, composting them first is generally easier to control.

Avoid thick layers on the surface

A large amount of compacted grounds on the soil surface is not a good idea.

Once dry, this layer can behave differently from the rest of the soil and hinder water penetration. If you use a little grounds as an amendment, it's better to spread them out and integrate them with other materials rather than forming a uniform crust around your plants.

Do coffee grounds really deter slugs and ants?

This is one of the promises most often associated with coffee grounds. It deserves to be rephrased.

Work cited by Oregon State University clearly shows an effect of caffeine on slugs and snails. Solutions containing enough caffeine can repel or kill them.

But this does not mean that a circle of used coffee grounds automatically forms a reliable barrier around your lettuce.

Brewed coffee, used grounds, and an experimental caffeine solution are not the same thing. Their caffeine concentration differs greatly.

We therefore prefer not to present coffee grounds as a guaranteed repellent against slugs, ants, or "all pests." If a problem persists in the garden, it is better to precisely identify the species concerned and use an appropriate method.

And to deter cats? Best to forget about it

You will also find advice recommending scattering grounds to prevent cats from coming into certain areas of the garden.

We do not endorse this tip.

Coffee and caffeine can be toxic to animals if ingested. Even if used grounds contain much less caffeine than unbrewed coffee, there is no reason to voluntarily make it a product intended to be placed in an animal's path.

If you live with a cat or dog, keep your coffee, beans, and leftover grounds out of their reach.

Use grounds for certain household chores

The texture of coffee grounds also opens up some possibilities in the house. Here again, it is necessary to distinguish a small practical tip from a universal cleaning product.

Test them as a light abrasive

The grains give the grounds a slightly abrasive texture. On certain robust surfaces, they can help remove residues in addition to classic cleaning.

For example, you can test a small amount of damp grounds on a heavily soiled container, then rinse thoroughly.

Always start on an inconspicuous area. An abrasive material, even a natural one, can scratch or dull certain surfaces.

Therefore, avoid grounds on fragile, shiny, porous, or scratch-sensitive materials. "Natural" does not mean "compatible with absolutely everything."

Can the refrigerator be deodorized with coffee?

Coffee is also used as a household deodorizer.

The U.S. Food Safety and Inspection Service of the USDA notably cites fresh ground coffee among the solutions that can be placed in an open container to help address persistent odors in an already cleaned refrigerator or freezer.

If you want to repurpose your used grounds rather than fresh coffee, dry them completely first. Damp grounds left forgotten in a container would simply become a new source of mold.

And most importantly, do not try to mask the source of a bad smell. Start by removing the affected foods and cleaning the refrigerator.

And for hand odors?

After handling garlic, onion, or other odorous foods, some people use a small amount of damp grounds to wash their hands.

The interest is mainly mechanical and sensory: the grain helps to rub the skin surface and the smell of coffee can temporarily replace some of the perceived odors.

Rub gently and rinse thoroughly. If your hands are irritated, cracked, or particularly sensitive, simply stick to a mild soap.

Can coffee grounds be used on the skin?

Yes, ground coffee can act as a mechanical exfoliant. But precisely because it's abrasive, you should avoid overdoing it.

Exfoliation involves removing some of the dead cells present on the skin's surface. It can give a smoother skin sensation, but it's not suitable for all skin types in the same way.

For the body, be very gentle

If your skin tolerates exfoliation well, a small amount of very fine grounds can be used occasionally on the body.

Make small movements without pressing hard, then rinse with lukewarm water.

The American Academy of Dermatology generally recommends being gentle with any mechanical exfoliation. Excessive exfoliation can cause redness and irritation.

So avoid rubbing until you feel "it's working." Red or painful skin is not proof of effectiveness.

Avoid scrubbing if your skin is irritated

Do not use grounds on a wound, sunburn, or an already irritated area.

Very sensitive, dry, or acne-prone skin may also not tolerate mechanical exfoliants well.

The face particularly deserves caution. A grain that feels pleasant on the legs can become far too aggressive on a more sensitive area.

Finally, coconut oil, olive oil, or any other oil added to a homemade recipe is not automatically suitable for all skin types. Testing a preparation on a small area remains more sensible than immediately applying a mixture to the entire face.

And for the scalp?

The initial draft recommended adding grounds to shampoo or conditioner to exfoliate the scalp and stimulate circulation.

We prefer not to make this a general recommendation.

The scalp can be sensitive, and coffee particles can be difficult to remove, especially in thick or curly hair. If you have dandruff, itching, lesions, or a scalp condition, a product formulated for that need will be more suitable.

Reusing waste is only interesting when the use remains genuinely relevant.

Turn coffee grounds into color for your creations

Coffee grounds have a characteristic that is much simpler to verify: they stain.

What is sometimes annoying on a tablecloth can become interesting in a creative project.

You can use coffee or damp grounds to give a brown tint to certain papers, cardboards, textiles, or objects intended for crafting.

Aging paper or cardboard

A little coffee allows you to quickly create an aged or patinated look on paper.

It's a simple idea for cards, creative packaging, labels, or craft activities.

Then let the support dry completely before handling it.

Testing a shade on fabric

Coffee can also change the color of certain fibers. The result depends heavily on the material, concentration, contact time, and treatments already applied to the textile.

So always do a test on a sample.

And do not present this technique as the equivalent of professional textile dyeing: the color and its wash resistance can vary.

Create without seeking perfection

This is probably where coffee grounds become most fun.

Leftover coffee doesn't need to become a high-performance or permanent product to find a second use. A one-off craft activity, tinted paper, or a creative experiment is already enough.

At KOOTA, coffee grounds already have a second life

Reusing grounds at home is one thing. Organizing their reuse in a real product is another.

KOOTA has notably worked with Savonnerie Möbius, in Hauts-de-France, to incorporate KOOTA coffee grounds into cold-process soaps.

The formulations followed a specific development process and were submitted for the validation required for their commercialization. The grounds are thus integrated into a cosmetic formulation designed as a whole, rather than simply added to an improvised recipe in a bathroom.

This is an important distinction.

A formulated and controlled soap containing coffee grounds is not equivalent to applying a homemade mixture of damp grounds and oil to the skin.

This example also shows what upcycling truly means: taking a material that has already fulfilled its first function and building a coherent new use for it.

Should you use whole bean or ground coffee?

To reuse the grounds, the principle remains the same: it's the coffee extraction that produces this damp material.

So you can recover grounds whether you've ground your own coffee or prepared pre-ground coffee.

If you grind your own coffee

Choosing organic whole bean coffee allows you to adapt the grind to your preparation method before recovering the grounds after extraction.

For a balanced cup, for example, you can start with a good whole bean coffee like the Harmonieux in a recyclable bag.

If you prefer a stronger cup, the Puissant is also available in 250g whole bean coffee.

And to stick with a pure origin, KOOTA also offers a Colombian whole bean coffee.

The taste changes. The rule after extraction, however, does not change: recover the grounds cleanly and choose their use before accumulating them.

If you use pre-ground coffee

An organic ground coffee bypasses the grinding step and also produces grounds after preparation.

The Harmonieux is thus available as a good ground coffee for those who prefer this format.

The Puissant is also offered as 250g ground coffee.

And the pure origin recipe exists as Colombian ground coffee.

Finally, you can discover several recipes with a coffee set. The best reuse of grounds remains the one that easily integrates into your daily coffee preparation routine.

What "false good ideas" should be avoided?

Coffee grounds have become a classic in "zero waste" tip lists. This has an advantage: we question more what happens to our waste.

But it also leads to an accumulation of promises.

A natural ingredient is not automatically an ideal fertilizer, pesticide, cosmetic product, deodorizer, cleaner, and fuel all at once.

Avoid presenting it as a complete fertilizer

Coffee grounds contain nutrients, but in insufficient quantities to replace a fertilization adapted to a plant's needs on their own.

In the garden, their easiest place to manage is generally within a diversified compost.

Do not accumulate it around plants

More is not better.

A large quantity of grounds directly on the soil can disrupt the functioning of the environment rather than improve it.

If you produce a lot, compost it gradually rather than emptying your coffee maker at the foot of the same plant every day.

Do not count on it as a universal repellent

The observed effects for certain caffeine concentrations do not allow us to conclude that used grounds automatically repel ants, slugs, snails, and other garden animals.

Identifying the problem remains more effective than multiplying improvised barriers.

Keep it out of reach of animals

Coffee and caffeine can cause poisoning in pets.

So, do not intentionally leave your coffee grounds in a saucer accessible to a dog or cat, even for a gardening tip.

Don't scrub your skin too hard

Mechanical exfoliation removes dead cells by friction. It is precisely for this reason that excessive rubbing can also irritate.

Occasional, gentle use on skin that tolerates it is very different from an energetic daily scrub.

Do not store damp grounds for weeks

If you don't use it quickly, dry it.

Otherwise, put it in the compost rather than creating a collection of small damp pots in the kitchen. Waste reduction should simplify daily life, not add a new chore.

So, what is the best use for coffee grounds?

There isn't one single good answer.

If you have a compost, it's probably the simplest option for regularly valorizing your grounds, provided you mix them with other materials and keep the quantities reasonable.

If you don't have a garden, you can occasionally keep some dried grounds for a creative activity or certain household uses.

If you like exfoliating treatments, opt for a gentle approach adapted to your skin rather than a recipe presented as miraculous.

And if none of these solutions fit your daily life, that's okay. A coherent approach isn't about finding a use for every waste product at all costs.

The most useful thing is to start with the actions that genuinely suit you: choosing your coffee, mastering your preparation, avoiding unnecessary consumables when possible, correctly sorting packaging, and valorizing organic materials when you have a suitable channel.

The coffee grounds have already done the essential: they gave you your coffee. Giving them a second life, when it makes sense, is simply the next step.