The plan to suck CO2 out of the atmosphere and use it to rebuild Earth’s coasts

Though the effects of climate change are becoming more apparent and threatening every year, the world’s most powerful nations are still not doing enough to combat the threat. We’re running out of time to change our way of life to meet this challenge, and some world leaders refuse to even admit there is a problem.

Even if we adopt much more aggressive policies to fight climate change sometime in the next few years, the amount of CO2 we’ll have already pumped into the atmosphere will continue to contribute to sea level rise, extreme weather events, and more. According to the United Nations’ Intergovernmental Panel on Climate Change (IPCC), we may need to invest in literally sucking CO2 out of the atmosphere to avoid climate change’s worst effects.

This technology, known as carbon capture, is still developing. There are multiple ideas for how it could be done — each with its own set of pros and cons. For example, we could suck CO2 out of the atmosphere and sequester it deep inside the Earth, but there are concerns that it could still leak out. We could also turn it into fuel, but doing so would ultimately mean we’re still burning carbon, so it’s essentially just carbon neutral, not carbon negative.

Climeworks

But lately, scientists and engineers have been mulling over a third option: Transforming the captured CO2 into limestone, which could then be used for a wide range of applications — from making concrete to rebuilding the world’s coasts.

From sequestration to transformation

Gaurav Sant, a professor of civil and environmental engineering at UCLA, tells Digital Trends that the science is pretty simple.

“Think about high school chemistry. Carbon dioxide (CO2) is what you would think of as an acid, and the moment you react it with a base, which is something caustic or something that is alkaline, you’re going to produce a salt and water,” Sant says. “The salt that you produce is essentially a rock, a common example of which is limestone (calcium carbonate).”

“You’re going to produce, give or take, somewhere in the vicinity of 100 billion tons of limestone if you convert all of the CO2 that we’ve emitted into the atmosphere [in one year]/.”

Sant says this limestone you’d create could be used for building materials, in pharmaceuticals, and it could even help address some of the effects of sea level rise if we used it for land reclamation. Land lost to sea level rise could actually be replaced using the limestone you get from sucking CO2 out of the atmosphere. One problem, though, is how much limestone we’d end up with if we went this route.

“We should keep in mind that the amount of limestone you’re going to produce is phenomenal,” Sant says. “You’re going to produce, give or take, somewhere in the vicinity of 100 billion tons of limestone if you convert all of the CO2 that we’ve emitted into the atmosphere [in one year] into rock.”

That’s a whole lot of limestone. Sant says we would need a sophisticated supply chain to make sure that limestone can be utilized properly. Another problem, Sant says, is simply the cost of sucking CO2 out of the atmosphere.

Juerg Matter

“The processes continue to be extremely energy intensive,” Sant says. “I think we’re still looking at average costs north of $250 per ton of CO2, and this is being very optimistic.”

We could power these machines with solar and wind power to get the cost down, but we’d need to make sure we have the battery technology to keep them powered, regardless of the weather. Sant says we need to invest more money into researching and testing this technology to see how we can get the cost to an affordable price tag.

“The big learnings come from actually doing,” Sant says. “We need to build several dozen plants, as an example, and as you build these plants and operate them, you realize all of the different ways that you could take costs out of the equation, so to speak.”

A better option: Stopping CO2 at the source

Michael Mann, a professor of atmospheric science at Penn State University, says we can’t forget what remains the most important solution to climate change.

“Of all geoengineering schemes, direct air capture is probably the safest and most efficacious, but it is currently far more expensive than the much more obvious and simple solution: Stopping the burning of fossil fuels,” Mann says.

We need to get off of fossil fuels as soon as we can, but we also need to invest in learning how we could get the CO2 that’s being pumped into the atmosphere as we speak and the CO2 that’s been there for a long time out of the atmosphere. If we can greatly reduce the cost of this technology and figure out what to do with all of the CO2 we capture, then we could get the climate back to a place where we’re not facing extreme heat, sea level rise, extreme weather events and more.

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