Used Coffee Grounds | What To Do With Them

We drink over 2 billion cups of coffee a day. Used coffee grounds are usually incinerated or sent to landfills – and in landfills, rotting coffee grounds generate methane, a greenhouse gas 28 to 34 times more potent than carbon dioxide. Is there a better way to recycle coffee grounds?

Who discovered coffee?

One legend says that around 850 AD, an Ethiopian goat herder observed his goats had an extra spring in their step after eating coffee cherries. He gave a sack of coffee cherries to a local monastery, and the dismissive monks tossed it onto a fire. They became enraptured by the delicious smell of roasting coffee beans. Or was it the canny hunters of Ethiopia’s Galla tribe who ate coffee cherries for energy? The earliest written record of coffee dates back to Rhazes (852 – 932 AD), a Persian physician. This is why ‘coffee’ and ‘cafe’ derive from the Arabic word, qahwa, which originally meant ‘wine’.¹

Fast-forward to the present day and the roasted pits of coffee cherries are ground into the familiar brown powder we see in shops today.  Beans are produced and traded by over 50 countries worldwide, with the Finnish drinking the most coffee per year–an average of 12.5 kg per person–closely followed by the Swedish.³ 

The flavour of coffee comes from the aromatic oils and acids in the ground bean, and most of the bean is insoluble. A cup of filter coffee may contain just 1.2% soluble coffee, leaving some 18 million tonnes of used coffee grounds produced each year. Our coffee-drinking habits are generating a lot of waste. But, perhaps ‘waste’ is a misconception.

The most expensive coffee is produced by letting elephants digest coffee cherries. It costs $1,100 per kilogram, due to the difficulty in recovering enough intact pits from the elephant dung.¹⁴

Extracting useful products from used coffee beans

One company dedicated to coffee grounds innovation, Biobean, says used grounds still retain up to a third of the volatile aroma and flavour compounds found in freshly roasted beans, which could be extracted to make natural flavour and fragrance products.⁵

Two Scottish entrepreneurs have also started a company, Revive-Eco, that focuses on the hidden value inside coffee grounds. 

“We can extract a number of different oils from the coffee grounds which have similar characteristics to palm oil – we have extracted these oils on a lab scale and know that they are there,” said Fergus Moore, co-founder of Revive-Eco.⁶

Find out how the company UpCycle converts food waste into beauty products 

Demand for palm oil by industries such as cosmetics, fashion and food has led to heavy and increasing deforestation in rainforest countries. Since 1973, nearly 16,000 square miles of rainforest on Borneo have been cleared for oil palm plantations - 47% of total deforestation there since 2000. Revive-Eco aims to improve its extraction technology to make coffee oil a competitive alternative.  

^{Used coffee grounds as fuel}

Bio-bean also processes coffee grounds into burnable pellets for industrial boilers and ‘coffee logs’ for household burners. Each log contains the equivalent grounds of 25 cups of coffee and burns longer than kiln-dried wood. 

Coffee oil can also be blended with other fuels to produce biodiesel. This fuel was trialled in London buses in 2017, with an estimated 2.55 million cups of coffee powering a single bus for a year.⁸

Burning coffee grounds produces 80% less emissions than putting them in a landfill.⁷

Creating fashion & everyday items with used coffee grounds

Image courtesy of Kaffeeform

Other entrepreneurs are turning coffee oil into wearable clothing. Two Vietnamese entrepreneurs produce sneakers using ‘coffee yarn’ at Rens Originals. Each pair is a mixture of oil from 21 cups of coffee and six recycled plastic bottles.⁹ Co-founder Jesse Kanh Tran reflected that it is still cheaper to make new things from raw materials instead of recycling waste but that sustainability is an added bonus for customers choosing designer goods.¹⁰

Grounds can also be made into useful household equipment. German company Kaffeeform, produce coffee cups and saucers from spent coffee grounds. Other companies are producing clothes from yarn infused with coffee particles, saying that as coffee has antibacterial properties, it could reduce body odour.¹¹

Composting used coffee grounds

Finally, do coffee grounds make good compost? Washington State University advises coffee grounds can provide nutrients and other benefits to soil, but compost should only be one-fifth coffee grounds, as too much coffee might actually suppress seed germination.¹² Perhaps the millions of tons of used coffee grounds produced daily should go back into our food system. Rotterzwam, a zero-waste farm in Rotterdam, is already converting 6,000 kilograms of coffee grounds each month into oyster mushrooms.¹³