The world’s oceans store enormous amounts of carbon dioxide. Recently, a team of scientists and companies claim to have found a way to increase this storage capacity by modifying the chemistry of ocean water.

The technique, known as enhancing ocean alkalinitytypically involves dissolving rocks that neutralize acids in the ocean, allowing it to absorb more carbon dioxide.

Researchers have been exploring this technology for the past five years, but in the past two months, at least a few startups have begun operating along the Atlantic and Pacific coasts. Planetary, a Nova Scotia-based start-up, removed 138 metric tons of carbon last month for Shopify and Stripe. The startup Ebb Carbon maintains a small site in Washington that can remove up to 100 metric tons of carbon a year, and committed in October to removing 350,000 metric tons of carbon from the atmosphere over the next decade for Microsoft.

Proponents of the technology say it is one of the most promising forms of carbon removal, which experts say will be necessary to meet climate goals even as the world cuts emissions.

But for that to make a dent, it would have to scale to remove billions, not hundreds of thousands, of metric tons of carbon annually, said Yale Associate Professor of Earth and Planetary Sciences Matthew Eizaman.

How it works

At its core, ocean alkalinity enhancement is a chemical reaction, one that already happens in the ocean all the time.

“The ocean is the largest carbon storehouse on the planet, and its ability to permanently store CO2 is based not only on its vast size, but actually on the natural alkalinity of seawatersaid Antonius Gagern, executive director of Carbon to Sea, an initiative that funds ocean alkalinity projects.

Today’s ocean is slightly alkaline at pH 8.2, in part due to the chemical weathering of limestone, basalt, and other rocks throughout Earth’s history.

Dissolved carbon dioxide in water reacts with these alkaline substances to form bicarbonate ions, a stable form of carbon that can trap the element for millennia, thereby reducing atmospheric carbon dioxide without causing ocean acidification. Then, to restore balance, the ocean absorbs more carbon from the atmosphere. This chemical reaction makes the ocean the planet’s largest carbon sink, a term that refers to a natural or man-made reservoir that absorbs more carbon than it releases.

The new technology aims to enhance this natural process by adding alkaline minerals to the water, either in crushed or dissolved form. After studying the potential of marine carbon removal technologies, the National Oceanic and Atmospheric Association found that enhancing ocean alkalinity was the most effective in long-term carbon sequestration and among the cheapest options.

Carbon removal could also help prevent ocean acidification. Although the ocean’s chemistry has varied over geologic time, it has become more acidic as it has absorbed more carbon from human emissions, said Andy Jacobson, a geochemist at Northwestern University. Increased acidity makes it difficult for some marine organisms to build their skeletons and shells.

“Theoretically, [η ενίσχυση της αλκαλικότητας των ωκεανών] it has many thingsJacobson said. “But more research is needed to determine how effective and how permanent carbon removal is».

Will the project start?

Climate ventures and philanthropic funders are spending millions of dollars to finance the strengthening of ocean alkalinity.

Researchers are still exploring the best strategy for implementing the method. Ebb Carbon, for example, takes existing saltwater waste streams from treatment and desalination plants and uses electricity to alkalinize them before returning them to the ocean, said Eisaman, who is the start-up’s co-founder and chief scientist.

Another method is to deposit alkaline minerals or solution into the ocean using a ship. Others want to enhance the erosion of rocks already occurring on the coast.

One of the biggest challenges is measuring how much carbon this can sequester. Alkaline minerals dissolve quickly in a large body of water, and it’s difficult to quantify the carbon removed, said Dariia Atamanchuk, a senior researcher at Dalhousie University in Nova Scotia who advises Planetary on carbon measurement.

Because questions remain about its impact on ocean ecosystems, any project will likely face opposition from the fishing industry. Communities on the east coast have pushed back against proposals, saying the impacts are not well understood.

“They should not throw anything into the ocean” said Beth Casoni, executive director of the Massachusetts Astacomana Association, adding that she is skeptical of “the idea that you can alkalize the ocean like your backyard pool».

Mounting evidence from early laboratory studies and controlled outdoor settings suggests no serious effects on plankton, which reside at the bottom of the food web.

Regulations from the Environmental Protection Agency would limit some impacts because, for certain types of ocean alkalinity enhancement, it limits the change in seawater pH that results from adding materials to a pH of nine, said Grace Andrews, executive director and founder of the non-profit organization. Hourglass Climate, which investigates ocean alkalinity and its environmental effects.

“Right now, most people are hesitant to say, ‘This is definitely going to be useful for marine life,’ simply because of the scale required to change entire oceans.“, he said. “But it certainly has the potential».