How an unassuming ‘sponge’ in your home could suck planet-heating pollution from the atmosphere

Scientists have found that an item widely used in kitchens can absorb planet-heating carbon dioxide from the atmosphere, in what they hope will become a low-cost and efficient tool to slow climate change.

Scientists from the University of Cambridge in England used activated charcoal — a sponge-like substance used in household water filters — and “charged” it like a battery to see if it would absorb carbon dioxide (CO2) directly from the air.

While activated charcoal can filter impurities in water, it wouldn’t normally be able to capture CO2. But scientists discovered this changed when they mimicked the process of charging a battery — in which ions stick to a battery’s electrodes — using chemical compounds called hydroxides.

Hydroxide ions accumulate in the tiny pores of the charcoal and start to form bonds with CO2, sucking it out of the atmosphere, according to the study published this week in the journal Nature.

Once the CO2 is absorbed, it then needs to be purified and stored to stop it being released back into the air. Scientists were able to separate the CO2 from the charcoal by heating the sponge to between 90 and 100 degrees Celsius (194 to 212 degrees Fahrenheit), breaking the bonds between the CO2 and the hydroxide ions.

It might seem like an energy-intensive process, especially for something designed to slow climate change, but some other methods to draw carbon directly from the atmosphere require temperatures as high as 900 degrees Celsius, often powered by natural gas, a fossil fuel.

The scientists say their technique requires far less energy and can be powered by renewables alone.

There are limitations to this method, however. The CO2 capacity of the sponge decreased as relative humidity increased, according to the study.

Scientists are also researching how to increase the amount of CO2 the sponge is able to capture.

The University of Cambridge Forse Group, a team of academics involved in the study, who research materials that can help reduce greenhouse gas emissions. - University of Cambridge
The University of Cambridge Forse Group, a team of academics involved in the study, who research materials that can help reduce greenhouse gas emissions. - University of Cambridge

‘It’s not a silver bullet’

Carbon capture methods have faced intense criticism in recent years from some experts who argue that the focus and resources should be on making dramatic cuts to fossil fuel use. Current approaches tend to be expensive, resource-intensive and unproven at scale.

But the United Nations’ Intergovernmental Panel on Climate Change, an authoritative body on climate science, says that at least some carbon dioxide removal will be necessary to reach net zero, where the world only emits as much carbon pollution as it absorbs.

“The first thing to say is we need to reduce our greenhouse gas emissions in every way possible. Coming up with processes that inherently don’t produce CO2 is what we should do first,” the study’s lead author, Alexander Forse from the Yusuf Hamied Department of Chemistry at the University of Cambridge, told CNN.

“I think the role that carbon capture can play is first with industrial CO2 emissions, things like producing cement, which gives off CO2 in the process,” said Forse.

Sucking up carbon dioxide directly from the atmosphere “is a last resort,” Forse added, “but given the scale of the climate emergency, it’s something we need to investigate.”

A recent report led by the University of Oxford said that 2 billion tons of CO2 are removed from the atmosphere each year, mostly through conventional methods such as tree planting. Modern technologies, like carbon capture, contribute less than 0.1% of the total amount of CO2 being removed, the report said.

To achieve the Paris Agreement’s goal of limiting global warming to well below 2 degrees Celsius above pre-industrial levels, the world needs to remove at least four times more CO2 from the atmosphere every year than current levels, according to the “State of Carbon Dioxide Removal” report published earlier this week.

Forse hopes their new method can be used for a range of applications and can be scaled up for use in the real world. Now Cambridge University is looking to commercialize the technology.

“This approach was a kind of crazy idea we came up with during the Covid-19 lockdowns, so it’s always exciting when these ideas actually work,” he said.

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