Leftover coffee 'can help fight global warming'

Research says coffee's ability to store methane could enable it to power homes

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Whether flat white, skinny latte or straight black Americano, a cup of coffee is the morning drink of choice for millions needing a power-up at the start of the day.

Researchers have now found that the huge amounts of leftover coffee grounds, which usually go into compost tips or waste bins, could be used to power homes and combat global warming, thanks to their ability to store methane.

The grounds are highly absorbent and scientists have developed a simple process which enables the grounds to absorb methane – a far more potent greenhouse gas than CO2 – from the atmosphere.

And the process has an added advantage since the resulting methane-heavy coffee mixture can be burnt to produce electricity, providing a source of energy that is cleaner than other fossil fuels, the scientists claim.

The process, developed by researchers at the Ulsan National Institute of Science and Technology in South Korea, involves soaking the waste coffee grounds in sodium hydroxide and heating the resultant mixture at up to 900C in a furnace.

The process is cheap because the raw materials are essentially free. It is also quick, producing an effective “carbon capture” material in less than a day – a fraction of the time it takes to make other carbon capture materials.

Perhaps not surprisingly, the idea came to the lead author of the paper while he was sipping a cup of coffee at work. “We were sitting around drinking coffee and looked at the coffee grounds and thought, ‘I wonder if we can use this for methane storage?’” says Christian Kemp, who has since moved to Pohang University of Science and Technology in Korea.

“The big thing is that we are decreasing the fabrication time and we are using cheap materials. The waste material is free compared to all the metals and expensive organic chemicals needed in other processes – in my opinion this is a far easier way to go,” he added.

The research is published in the journal Nanotechnology and is based on tests using spent coffee grounds – 100 per cent Colombian coffee, dark roast, fine ground – which the scientists obtained “in house”.

This is not the first time coffee grounds have been used for environmental purposes. Elsewhere, they have been turned into biomass pellets that can be burnt to create a relatively clean form of energy.