September 16, 2020

What Happens To Coffee Grounds After They’re Used?


We know that the coffee industry has an impact on the environment. Every step of the coffee supply chain, from growing and processing to shipping and roasting, uses energy in some capacity and therefore has its own carbon footprint – including used coffee grounds.

They are an unavoidable byproduct of coffee consumption. And while many of us assume it’s safe to toss grounds out with other organic waste, that often isn’t the case. Grounds can actually have a significant impact on the environment when they end up going to landfill.

Here’s what happens to used coffee grounds that are thrown away, why they’re bad for landfills, and how the average coffee drinker might be able to repurpose them.

You may also like our article on whether you can you run a zero-waste coffee shop.

Used coffee grounds

How Much Coffee Waste Do We Produce?

According to the SCA, the “golden ratio” for brewing coffee is 55g per litre. This works out at just under 14g for a 250ml cup. While this might seem individually insignificant, billions of cups of coffee are consumed every single day. 

Hector Nunes is a researcher and Ambassador for BeKoffee, a company that makes products from used coffee grounds. He tells me that in Portugal, the average 2022 coffee consumption per capita was 4.6kg. With Portugal’s population of just over 10 million, this ends up being more than 46,000 metric tons a year. 

Hector says that while some countries repurpose their coffee waste, about 75% of it ends up going to landfill. Most of the remaining 25% is reused to make agricultural products like fertiliser. 

Melanie Gosling is the founder of espresso caravan Tipple & Tamper in Queensland, Australia. She says Australia creates about 65,000 tonnes of coffee waste every single year. Most of this goes to landfill. Furthermore, Melanie adds, this doesn’t take into account other forms of coffee waste – just the grounds left behind from brewed coffee.

What Happens When Coffee Grounds Reach Landfill?

The majority of used coffee is thrown directly into the bin without being separated or treated. After being thrown away, it will end up going to landfill. At this point, it will be at least three months before the coffee grounds start decomposing in the landfill’s anaerobic environment. 

Hector says: “Coffee grounds contain oils and other compounds that makes the soil more acidic. In landfills, this creates an acidic leachate (liquid) which can damage the surrounding soil.

“In addition to this, the decomposition of coffee waste in landfills also generates greenhouse gases,” Hector adds.

These gases have a further effect on the environment and contribute to climate change. Melanie says: “When coffee grounds are dumped into landfills, they create methane, which is a greenhouse gas. Methane is known to be more harmful than carbon dioxide.”

So, what can we do instead of throwing our coffee waste away? Well, most used coffee grounds are disposed of before their full value is extracted. According to bio-bean, the UK’s largest recycler of coffee grounds, spent grounds retain more than a third of their volatile flavour and aroma compounds after brewing.

They also point out that coffee grounds are also high in calorific value. While they can’t be eaten, this means that they are a potential energy source.

bio-bean say that coffee grounds burn “20% hotter and longer” than dry wood fuels. They also have a lower carbon footprint when compared to traditional fossil fuels.

Why Is It So Difficult To Keep Coffee Grounds Out Of Landfill?

A number of organisations have taken note of the “unseen” value of used coffee grounds. As well as bio-bean, who collect and recycle coffee waste across the UK, there are a number of other organisations around the world who repurpose coffee grounds for other uses.

For instance, UpCircle uses coffee waste among other natural ingredients to create skincare products. Another company, Kaffeeform, uses them to create sustainable coffee cups and saucers.

Hector says: “Spent coffee grounds have a high potential, both in terms of organic composting and in terms of energy recovery and the production of new materials. 

“They are already used to produce biodiesel and pellets for heating. Soon, they will no longer be a simple waste product, and instead be considered as a raw material for industry.”

According to Hector, there is economic potential for used coffee grounds to be repurposed on a wider scale. However, the cost of organising such an initiative would be difficult, and it would require a great number of stakeholders (including coffee shops) to buy in. Furthermore, even if grounds are not repurposed, industrial-scale composting and recycling initiatives are costly and require a significant investment in infrastructure. 

A 2018 paper by the British Coffee Association (BCA) on barriers and opportunities in the coffee industry says: “Although [consumer waste] is much smaller in scale than more commercial waste… the action of individuals is critical in producing long-term changes in behaviour.”

Hector explains that while some countries are starting to collect coffee grounds to be treated and reused, most do not have the systems in place to do so. As such, in many countries, the only possible outcomes are landfill, home reuse, and composting.

Reusing Coffee Grounds At Home

So, if large-scale recycling or composting schemes are difficult to access, then what are the opportunities for home reuse?

A brief internet search will show dozens of different ways to repurpose used coffee grounds at home, ranging from using them as a natural exfoliating scrub to neutralising odours in your fridge. 

However, one of the easiest and most practical ways to reuse coffee waste is to repurpose them as fertiliser for plants. Mandy and Gus Arnett own Green Bear Coffee, a coffee shop in New Zealand. They say: “Home consumers should be disposing of their coffee through their own composting or onto their plants.” 

Mandy and Gus add that their coffee shop “offers free coffee grounds to customers”, who can “bring their own container and fill from [their] grounds bin”.

Coffee grounds are rich in nitrogen and naturally repel a number of common garden pests. They can even be used to create “barriers” which slugs and snails can’t crawl over. Over time, used grounds can also improve the quality of your garden’s soil, and can be used repeatedly and indefinitely without diminishing returns.

However, to get the full value from used grounds, they should be composted for at least 100 days to reduce their levels of caffeine, chlorogenic acid, and tannins. If you have a compost bin where you keep other used food, add your grounds there. 

Soil fertilised with composted coffee grounds is most suitable for plants that grow well in slightly acidic soil, such as lilies and blueberries. It should also be kept away from pets, as it can be dangerous if consumed. 

With global coffee consumption expected to grow by 3.3% to 170.3 million 60kg bags in 2022/23, carbon emissions and waste from the coffee industry will undoubtedly increase, too.

By responsibly disposing of natural byproducts, like used coffee grounds, everyone across the supply chain can do something to mitigate the negative environmental effects of their coffee consumption.

Even though reusing coffee grounds at home might seem like a relatively small step, it’s one that could still make a difference.

Enjoyed this? Then read our article on how coffee shops can reduce single-use cup waste.

Photo credits: Ana Valencia 

Perfect Daily Grind

Some statistics in this article were updated in December 2022.

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