Can you recycle used coffee grounds?

In recent years, brewing coffee at home has seen a massive surge in popularity. Whether you’re making filter coffee or pulling espresso shots, it is now easier than ever to make a great cup of coffee from the comfort of your home.

However, every cup of coffee you brew creates waste, including the spent coffee grounds that you’ve extracted those delicious flavours and aromas from. Every year, we produce millions of tonnes of used coffee grounds, the vast majority of which are sent to landfill. But is this truly necessary?

Read on to learn more about what you can do to recycle or repurpose your used coffee grounds instead of throwing them away.

Why do we need to recycle coffee grounds?

For many households around the world, used coffee grounds just end up in the trash. While a percentage of our coffee waste does get repurposed or reused, it’s estimated that as much as 75% goes straight to landfill.

This is a problem. Coffee contains a number of natural acidic compounds with an average pH value of 4.85 to 5.10. Even after brewing, a significant number of these compounds remain.

When used coffee sits in a landfill for months on end, these acidic compounds leach out from the spent grounds into the surrounding soil and damage it. Alongside this, when coffee waste does eventually break down in a landfill’s anaerobic environment, it releases methane – a greenhouse gas which is considerably more damaging than carbon dioxide.

This has an adverse effect on people all around the world, including the farmers who grow the coffee we love to drink. Arabica coffee – which represents around 60% of global coffee production – thrives between 64°F to 69°F (18°C to 21°C).

This makes it especially susceptible to climate change, and is already forcing coffee producers to climb to higher elevations in search of cooler temperatures.

So, what can we do to dispose of coffee waste in a more sustainable and responsible way?

Coffee industry initiatives: Recycling coffee grounds

Although it might not look like it, your coffee waste can be repurposed at scale in a number of different ways.

As coffee grounds are highly calorific, they make a great source material for biofuel. While traditionally plants like sugarcane or corn are used, growing crops for the express purpose of harvesting them for fuel leads to further environmental issues – like deforestation.

By using spent coffee grounds, we can repurpose something which would otherwise be thrown away. Biofuels are also a more sustainable alternative to emission-heavy fossil fuels such as petroleum or coal.

While reusing coffee waste as a fuel source is by no means a mainstream option, it is becoming a more realistic possibility with every passing year.
Around the world, there are a number of different organisations who manage collection schemes to gather spent coffee grounds on a massive scale. Every year, they save millions of tonnes of coffee grounds from going to landfill. These can then be dried and repurposed as fuel pellets, for instance.

However, coffee waste-based biofuel alternatives are not currently in widespread use around the world, and they require complex manufacturing infrastructure to process.

Other brands have opted to tackle coffee waste from a different angle. When dried, preserved, moulded, and polished, used coffee grounds can be repurposed to make all kinds of household items – including mugs, cups, and dishes.

So, we know there are industry initiatives to help repurpose coffee waste. But what about on a smaller scale? What can you do from home to make your coffee habit more sustainable?

How can you repurpose used coffee grounds at home?

Firstly: compost it. Coffee grounds are a great resource for gardening. This is by far the most common way in which coffee waste is reused at home.
However, home coffee consumers often make one critical mistake when using coffee waste as a natural fertiliser: dropping freshly-used coffee grounds straight onto their soil.

Even after their flavours and aromas have been extracted, coffee grounds are highly acidic, nitrogen-rich, and full of caffeine – which is toxic to some plants and animals.

By dumping your used grounds straight from the coffee machine onto your soil, you can hinder plant growth and even kill off useful bacteria in the soil.
There is a workaround, though. Compost your grounds for at least 100 days to allow time for the caffeine and acidity levels to drop. Mix them in with other organic materials, too – coffee waste should make up no more than 10% to 20% of the total compost volume.

Another option is to use coffee waste as a natural insecticide. Coffee waste is highly toxic to certain insects, including some species of mosquitoes and most slugs.

Leave a few bowls of used coffee grounds near your window as a natural repellent, or use it to create “barriers” around the soil and protect your plants.
Beyond their uses in the garden, spent coffee grounds can also be used as a body scrub (as as a natural exfoliant and to unclog your pores) and to neutralise unpleasant odours in your refrigerator. 

While it only makes a minor difference on an individual level, repurposing your coffee waste is a small step towards a sustainable future for the coffee sector.

Whether you use it as compost, an exfoliant, or a fuel source, it’s better than simply sending your used grounds to landfill.

So, next time you brew a cup of filter coffee or pull an espresso shot at home, think twice before throwing your coffee grounds away. You might just find another, more sustainable use for them.