Concrete traps CO2 soaked from air in climate-friendly test
A California startup using rocks to soak up carbon dioxide from the air has teamed up with a Canadian company to mineralize the gas in concrete, a technological tie-up that is a first and they say could provide a model for fighting climate change globally.
UN scientists concluded that removing billions of tons of carbon dioxide already in the atmosphere, in addition to cutting current emissions, will be necessary to limit climate change. To do that, two things are needed: first, capturing carbon dioxide with nature or technology, and second, locking it up for centuries.
Companies are springing up to do both.
Heirloom Carbon Technologies delivered about 30 kg (66 lb) of CO2 collected from the air around its San Francisco Bay Area headquarters to neighboring Central Concrete, a Vulcan Materials' VMC.N subsidiary that on Wednesday incorporated the gas into new concrete. That's equivalent to tailpipe emissions of driving about 75 miles (120 km) in a car.
The joint effort between Heirloom and Canada's CarbonCure Technologies was the first time that carbon dioxide absorbed from the atmosphere using such Direct Air Capture (DAC) technology had been secured in concrete, where the CO2 will stay put for centuries, several scientists said.
"Today this is a thimbleful of emissions abatement. You know, that's how it starts," said Julio Friedmann, chief scientist at Carbon Direct, which works with companies to manage their carbon footprint. Because concrete is so widely used, it has great potential for absorbing CO2, if the process works and goes global. "The thing about direct air capture and concrete is it's a big prize together," he said.
Heirloom heats crushed limestone to release naturally absorbed CO2, then puts the CO2-starved rock on columns of huge trays, where they act like sponges, soaking up close to half their weight in the gas over three days. The rock is then heated to release the collected ambient carbon dioxide, and the cycle repeats.
"Limestone has this natural ability to pull carbon out of the atmosphere. The problem is it's just slow. So what we do here is just give it more superpowers to make it pull carbon much, much, much faster than it otherwise would," said Heirloom CEO Shashank Samala.
CarbonCure, the concrete technology company, mixes CO2 with concrete ingredients, turning it into a mineral that strengthens the concrete, cutting the need for cement — the part of concrete with the biggest carbon footprint.
This week, CarbonCure incorporated the gas into water used to clean out trucks. The CO2 reacted with leftover ingredients and then was put into a new batch of concrete.
Capturing and locking down carbon on a global scale will not be easy though: companies like Heirloom will have to build expensive, massive plants capable of capturing millions or billions of tons a year.
"To remove a billion tons from the air we need in the order of mid-hundreds of billions of dollars," said Samala, who expects funders of solar, buildings, transmission towers and other infrastructure to finance carbon infrastructure, too.
The price of carbon also needs to fall. The US government and industry broadly see $100-a-tonne carbon dioxide as a reasonable price for broad deployment. Heirloom charges around $1,000 now; Samala expects to be at $100 by the time his projects are soaking up millions of tons a year.