​Could removing carbon from the ocean be a climate change solution?


Dante Simonetti, associate director of UCLA’s Institute for Carbon Management, explains the electrochemical reactor that kick-starts the first-of-its-kind carbon-removal process from seawater. (Gina Ferazzi / Los Angeles Times)

This article was originally published by The Los Angeles Times

Hello there! It’s Rosanna Xia, coastal reporter for the Los Angeles Times, filling in for Sammy Roth.

When an email from UCLA landed in my inbox, inviting me to check out an ocean-based carbon-removal system that its engineering faculty had just developed, I was (to say the least) very intrigued.

The ocean, after all, has long been a silent hero when it comes to climate change. It has absorbed almost one-third of the carbon dioxide released by humans since the Industrial Revolution — and more than 90% of the resulting heat. Talk long enough to anyone who works in marine science, and you’ll inevitably hear someone sigh and explain that this issue often flies so under the radar that it’s now dubbed “the other CO2 problem.”

This excess heat from unchecked carbon emissions has unfolded in insidious ways underwater.Sea level rise. More intense marine heat waves. And when carbon dioxide mixes with seawater, it undergoes chemical reactions that increase the water’s acidity, which can discombobulate fish and wreak havoc on marine ecosystems. Our coral reefs are dying, and scientists have also found that harmful algal blooms are getting more toxic — and occurring more frequently.

In the year 2021 alone, the world’s oceans got hotter by about 14 zettajoules. This is a mind-bending number, so thermal scientist John Abraham, at the University of St. Thomas in Minnesota, put it this way in an op-ed in the Guardian: “The oceans have absorbed heat equivalent to seven Hiroshima atomic bombs detonating each second, twenty-four hours a day, three hundred sixty-five days a year.”

So with all that in mind, I took a tour Wednesday of what has been billed as a game-changing, first-of-its-kind technology in removing carbon dioxide from the ocean. The pilot system, dubbed SeaChange, essentially pumps in seawater, extracts the carbon dioxide, and then, through a surprisingly simple process, converts the CO2 into a solid mineral that can be stored safely away. This in turn frees up the ocean to absorb more carbon emissions from the atmosphere. It’s a multimillion-dollar idea that researchers from the UCLA Samueli School of Engineering have been putting to the test.

Gaurav Sant, director of UCLA’s Institute for Carbon Management, center, associate director Dante Simonetti, left, and technical leader Thomas Traynor gather at AltaSea in the Port of Los Angeles on Wednesday to explain their team’s new carbon-removal technology.(Gina Ferazzi / Los Angeles Times)

It was a drizzly, gray morning as we gathered along the docks of the new AltaSea campus at the Port of Los Angeles, but spirits were high. Gaurav Sant, the director of UCLA’s Institute for Carbon Management, beamed with excitement as he talked about all the pieces to the electrochemical reactor and explained the intricate rebalancing systems that his team had designed and built atop a 100-foot-long barge.

To start the carbon-removal process, the researchers first run an electrical charge through the water. (Seawater, I learned that day, holds about 150 times more carbon dioxide than air per unit of volume). The electrolysis makes the water alkaline, which initiates a series of chemical reactions that ultimately neutralizes and traps the carbon dioxide into calcium carbonate — a fine powdery mineral that is found in seashells and limestone.

“The process relies on really simple, really elegant chemistry,” Sant said, adding that he was particularly proud of how remarkably energy efficient his team was able to make this whole operation. In a unique twist, hydrogen also gets created as a co-product, which helps power the carbon-removal equipment. (For every 220 metric tons of seawater that gets processed, about one metric ton of CO2 gets removed, while simultaneously producing about 35 kilograms of hydrogen.)

And get this, it’s not only the carbon-free seawater that gets released back into the ocean. The calcium carbonate also gets returned to the seafloor. It seems counterintuitive to put this hardened carbon back into the ocean, but Sant explained that this is a natural mineral that belongs to the inherent balance of the ocean. And considering that the ocean covers more than 70% of the surface of the planet, this method of storage is arguably more scalable than if we tried to store carbon underground.

The journey ahead is long, and how to scale this operation is still being worked out, but Sant said we owe it to ourselves to try. To really make a difference in climate change, we would need to remove at least 10 billion to 20 billion metric tons of carbon dioxide per year. This would require at least 1,800 industrial-scale versions of what Sant’s team has developed, costing many, many more millions of dollars.

As I held up a jar filled with this cloudy limestone slurry, it was humbling to think of all this carbon dioxide hardened into powered rock — carbon dioxide that has caused so much uncertainty over just how livable our planet will be in the future. At a time when climate anxiety and even grief have pushed its way into our collective consciousness, it was striking to see so much excitement (and dare I say, hope?) from engineers who really feel as though they’ve cracked one piece of the code to this global crisis.

“The oceans are the world’s largest sink of carbon dioxide emissions,” Sant said. “The ability to couple an engineering intervention with such an incredibly large natural system is one of the only ways we’re going to be able to tackle a problem this large, in terms of size and scale.”