Called Celour, the paint can sequester 27 grams of CO2 for every 135 grams of paint used.
“That is the same amount of carbon dioxide that a normal tree absorbs per day,” Kim said.
The indoor-outdoor paint is made of waste concrete powder, a cement-based residue from concrete recycling that is normally buried in landfills, where it can alkalise the soil and have a detrimental effect on local ecosystems.
Through a chemical process called mineral carbonation, which takes place when the paint reacts with the CO2 in the surrounding air, Kim says Celour can reabsorb a significant part of the emissions that were generated by producing the cement in the first place.
Eventually, she hopes to optimise the capturing capacity of the paint so that it completely negates the carbon footprint of the cement it is made from.
“I think it is too early to describe Celour as carbon neutral,” Kim said. “It needs further study but I want to make it a carbon-negative product. That is my goal.”
“It’s not enough if we just stop emissions, as we already have high levels of CO2 in the air,” she added. “We need to participate in CO2 removal in our daily lives.”
Concrete naturally reabsorbs some of the carbon it emits
Cement is the most carbon-intensive ingredient in concrete and is responsible for eight per cent of global emissions.
But when concrete is recycled, only the aggregate is reused while the cement binder is pulverised to create waste concrete powder and sent to landfill, where it can disturb the pH balance of the surrounding soil.
“Waste concrete powder is high in calcium oxide,” Kim explained. “And when it is buried and comes into contact with groundwater or water in the soil, it turns into calcium hydroxide, which is strongly alkaline.”
With her graduate project from the Royal College of Art and Imperial College London, the designer hopes to show the usefulness of this industrial waste material by maximising its natural ability to capture carbon.
Studies have shown that cement already reabsorbs around 43 per cent of the CO2 that is generated in its production through the mineral carbonation process.
This is set off when concrete is cured by adding water, which reacts with the calcium oxide in the cement and the CO2 in the air to form a stable mineral called calcium carbonate or limestone.
A traditional concrete block continues to cure throughout its life but because this process is reliant on exposure to air, only its outer layers will react with the CO2 while its core will remain uncarbonated.
Celour could store carbon for thousands of years
But Kim was able to improve the material’s carbon-capturing capabilities by turning the waste concrete pounder into a paint, mixed with a binder, water and pigments.
This is spread thinly on a surface so that more of the material is exposed to the air and can carbonate….”