Coffee grounds for cleaning: what's true – and which hacks to skip

They pile up every day, cost nothing and are supposed to absorb odours, scrub pans and clean drains: using coffee grounds for cleaning is a popular tip on forums and social media. But not every hack lives up to its promise – and some actually do damage.

Here you'll find out what they are really good for around the home, where they stain or scratch surfaces, and why they should never go down the drain.

What coffee grounds can and can't do for cleaning

Coffee grounds are finely milled, spent bean residue. Three properties make them interesting at home: they are slightly gritty and scrub gently, they are porous and can absorb odours, and they smell of coffee themselves. At the same time, they are dark, moist and still contain a little oil. That's why they stain, go mouldy quickly and don't dissolve grease.

Many online hacks confuse masking with cleaning. The Swiss consumer protection foundation (Stiftung für Konsumentenschutz) recommends a few simple household remedies such as vinegar, soda crystals, bicarbonate of soda and soap instead of lots of specialist products. Grounds are an extra for a few specific jobs, not a replacement.

1. Absorbing odours: only when dried

In an open bowl in the fridge, the shoe cupboard or under the sink, they can take the edge off unpleasant smells, and their own scent covers the rest. The key is that they are dry:

1. Spread the grounds thinly on a plate or baking tray.
2. Leave them to dry for a few days somewhere warm and airy, stirring now and then.
3. Put them in an open bowl or jar and place it in the fridge.
4. Replace them after about a week and check for mould.

This doesn't remove the cause, though. If the fridge smells, look for spoiled food and clean the inside, the seals and the drainage channel. Our guide clean the fridge shows how.

2. A scrub for grill grates and sturdy pans

The fine grit makes them a gentle scouring agent, a bit like salt. That suits sturdy surfaces with burnt-on residue:

• Stainless steel or cast iron grill grates: put damp grounds on a brush or sponge, rub off the residue and rinse thoroughly. Dry cast iron afterwards and oil it lightly.
• Sturdy pots and roasting tins: after soaking, rub burnt-on patches with a little of the grounds.

They are not suitable for glass-ceramic and induction hobs, non-stick pans, glass, acrylic or polished surfaces – the particles can leave scratches there. More methods for the grate are in our guide clean a barbecue.

If you clean the grate outdoors, don't let the rinse water run into an outdoor drain. The platform of the cantonal energy and environment offices points out that in a separate sewer system rainwater from roads, squares and terraces flows untreated into rivers and lakes. Grease and cleaning products belong in the sewer via the sink.

3. Removing smells from your hands

After chopping onions, garlic or fish, rub your hands with a few damp grounds and then wash them with soap. They absorb some of the smell and their own scent covers the rest. If your skin is sensitive or broken, it's better to skip this.

4. Never down the drain – the most important point

The tip that coffee grounds clean the drain or banish smells from the pipe is stubborn – and wrong. The opposite is true. They don't dissolve; they settle in the trap and pipes and combine with grease and soap residue into a dense plug. The more goes down, the greater the risk of a blockage.

• Knock or wipe the grounds out of cups, jugs and portafilters into the bin first, then rinse.
• Throw filters and grounds from the coffee machine straight into the bin.
• If the sink drains slowly, clean the trap instead of rinsing more.

What to do about a blocked sink is explained in our guide blocked kitchen sink.

5. Dispose of and reuse them properly

Where they go depends on your commune: some accept them with green waste, others don't. Swiss Recycle offers an overview of what is collected where in Switzerland and refers you to your commune's waste calendar for the details. If green waste isn't an option, they go in the official rubbish bag.

In your own compost, or mixed in small amounts into potting soil, they can still be useful. Don't spread them in a thick layer on the soil, or a mouldy crust will form. Plastic or aluminium capsules and pods don't belong in green waste.

Common mistakes

• Putting them in the fridge damp: instead of absorbing odours, they go mouldy.
• Rinsing them down the drain: the most common and most expensive mistake, leading to blockages.
• Scouring delicate surfaces: glass-ceramic and coatings get scratched.
• Using them on light surfaces: grout, fabrics and wood can turn brownish.
• Only masking smells: a scent is no substitute for cleaning – the source of the smell has to go.

Priority Clean editorial teamOur cleaning team from Alberswil, Canton of Lucerne, shares hands-on experience from move-out, house, office and window cleaning across Central and Northwestern Switzerland.