How the ocean could be key to carbon-capturing technologies to fight climate change

The ocean covers more than 70% of the planet. And unfortunately, it is rapidly acidifying thanks to harmful carbon dioxide emissions emitted from industrial smokestacks, the exhaust pipes of gas-guzzling vehicles and other modern technologies, and then absorbed by seawater. About 22 million tons of carbon dioxide end up in the ocean every day. The resulting acidification threatens countless marine species that are part of an ecosystem that humans depend on.

Sharply reducing and eventually eliminating the use of fossil fuels will help slow the acidification process. But the question also raises an intriguing prospect: what if we could use the ocean to fight climate change and perhaps even reverse this process? What if the ocean could be used as a carbon dioxide sink, removing it from the climate change equation indefinitely?

When people talk about capturing carbon from the atmosphere, they’re usually referring to what’s called direct carbon capture from the air, which aims to pull carbon dioxide from the air (or sequester it before it gets into the air) and store it. . Storing it often involves pumping it into a geological reservoir where it will hopefully remain indefinitely.

Unfortunately, it is still an expensive technology and there is a risk of carbon dioxide leakage. You also need to have access to a geological reservoir where you can store carbon dioxide.

Last December, the National Academy of Sciences released a report that assessed the feasibility of various proposals that focused instead on the role of the ocean in carbon sequestration. One plan, called ocean alkalinity enhancement, would grind up igneous rocks found on shorelines around the world to make the oceans less acidic and more basic (or more alkaline). Theoretically, this would not only solve the problem of acidification and make the oceans healthier, but also allow these waters to absorb excess carbon dioxide from the atmosphere and prevent it from acting as a gas. Greenhouse effect.

“The ocean contains about 50 times more inorganic carbon than the atmosphere due to its high alkalinity,” said Scott Doney, a University of Virginia marine scientist who chaired the National Academy of Sciences panel. , to the Daily Beast. “It has been suggested that if you increase the alkalinity of the ocean…you could potentially increase the ocean’s ability to remove carbon dioxide from the atmosphere.”

Doney noted that these types of igneous rocks are eroding into the ocean all the time, so we already know their ecological effects pretty well. He suggests that we could start using an electrochemical process to simply accelerate this erosion on the shoreline to increase the effects. When you increase the alkalinity of seawater, Doney said, chemical reactions cause carbon dioxide absorbed by ocean water to transform into other molecules that remain stored in the ocean.

Obviously, you can’t do this in one area and expect the world’s oceans to become less acidic. Doney emphasized that this should be a global project.

“We are at an inflection point where carbon management is going to be one of the greatest challenges for humanity and society for the next century and beyond.”

— Gaurav Sant

A bigger obstacle to turning the oceans into a giant carbon dioxide sequestration machine might be the fact that we still don’t know what kind of negative impacts to expect on such a large scale and how long they would last.

“We know that seawater acidification can have negative effects on marine life,” Doney said. “Maybe a big alkalinity dump could, too. We just haven’t studied that in detail.

Another proposal for using the ocean as a carbon sponge is to induce electrolysis (splitting water into hydrogen and oxygen) to remove carbon dioxide from the water and lock it into mineral salts called carbonates. Gaurav Sant, professor of civil and environmental engineering at the University of California, Los Angeles, will test such a method in a new startup project called SeaChange.

“We do it in two ways,” Sant told The Daily Beast. “We do this by taking carbon dioxide from seawater and locking it into mineral carbonates, and we do this by producing mineral hydroxides, which slightly increase the alkalinity of seawater.

“Since the carbon dioxide absorption capacity of seawater is related to its pH, a slight increase in its alkalinity allows you to extract additional carbon dioxide from the atmosphere,” he said. -he declares.

Gaurav Sant holding a piece of a new concrete his lab has developed to fight climate change.

UCLA Samueli School of Engineering

The mineral carbonates that contain the sequestered carbon dioxide can be released into the ocean, “where they would remain stable,” Sant said. This means that this mineralized carbon dioxide will not simply be released into the seawater. Given the amount of carbon the ocean can absorb in addition to the air, Sant believes this technology will be affordable for widespread use. if it can be demonstrated and proven safe.

Rapid adoption of this approach would involve integrating it into desalination plants around the world that absorb seawater. Sant and his team are on schedule to pilot the SeaChange technology in Los Angeles and Southeast Asia. Is later this year. He said these demonstrations would remove between 100 kg and 1,000 kg of carbon dioxide from the ocean per day.

“As we added carbon dioxide to the atmosphere over the past 200 years and the oceans absorbed that carbon dioxide, the oceans became acidified. At high levels, the average pH of the ocean rose from a pH of 8.2 to a pH of 8.1,” Sant said. “The SeaChange process does not involve drastic changes or interventions in the oceans. What we’re really talking about is slightly increasing the alkalinity of the oceans, on a large scale, which allows you to increase the carbon dioxide storage capacity of the oceans themselves.

In other words, this process would return ocean pH to what it was at the start of the Industrial Revolution about 200 years ago, undoing two centuries of damage caused by human activity.

That doesn’t mean we should completely reject the idea of ​​doing direct air capture. It will become cheaper over time, and it could be done while ocean-based methods are also used. Clearing the atmosphere would be a huge effort, so the best strategy puts everyone on deck.

“We’re going to need a portfolio of approaches,” Doney said.

Critics of carbon capture technologies will often say they are dangerous because they could be used as an excuse to keep burning fossil fuels. If we are to defeat climate change, we must eliminate the use of fossil fuels as soon as possible, but we must also do something about the excess carbon dioxide that will linger in the atmosphere for decades to come. Without capturing and sealing some of this carbon, global warming will continue to advance and wreak havoc on the planet.

“We are at an inflection point where carbon management is going to be one of the greatest challenges for humanity and society for the next century and beyond,” Sant said.

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