Why using the oceans to suck up CO2 might not be as simple as hoped

Meanwhile, several additional studies recently raised doubts about a different ocean-based approach: growing seaweed and sinking it to suck up and store away carbon.

Finding viable ways to pull down greenhouse gases will be vital in the coming decades. A National Academies report in December on ocean-based carbon removal noted that the world may need to suck up an additional 10 billion tons annually by midcentury to limit warming to 2 ˚C.

Boosting ocean alkalinity could theoretically remove tens of billions of tons each year on its own, according to the research group Ocean Visions. But the National Academies panel noted that it will require extracting, grinding, and shipping rocks on roughly similar scales, all of which would have substantial environmental consequences as well.

The new studies haven’t delivered the final, definitive word on whether any of these methods will be feasible ways of helping to reach those carbon removal targets.

But Michael Fuhr, one of the authors of the olivine study and a doctoral student at GEOMAR, says their findings do suggest that this approach is “not as easy as expected until now.” He adds that it may work well only in certain places where the ocean chemistry is right. That could include areas where the waters are low in salinity but rich with organic sediments, which will increase acidity.

Fuhr and others say that additional lab experiments and fieldwork will be needed to determine how well this method works in the real world, what the ideal conditions are, or whether other materials are more promising.

Maria-Elena Vorrath, a researcher at the Alfred Wegener Institute for Polar and Marine Research, said in an email that the study shows the olivine process does not work the way we assumed. But she stressed that the mineral remains “one of the most permanent and promising methods nature gives us.”

“We just need to understand and read the manual,” she wrote, noting that water mixing and other variables in the actual oceans could alter results seen in the lab.

One company, Project Vesta, has been planning to conduct a field trial in the Caribbean for several years, which would entail spreading olivine sand along beaches or in shallow waters. It’s also been carrying out lab experiments, toxicology testing, and planning for field trials on the east coast of the US, says Tom Green, the company’s chief executive officer.

Project Vesta began as a nonprofit but is now a so-called public benefits corporation, which means it has the twin goals of making a profit and achieving social good. The hope is to eventually sell carbon credits for any greenhouse gas removed with olivine, Green says.

A handful of additional startups are working on other ways of boosting ocean alkalinity, through approaches including electrochemical processes. Those include Ebb Carbon, Planetary Technologiesand Seachangeall of which have pre-sold tons of carbon removal they expect to achieve to companies including Shopify and Stripe.

Meanwhile, the National Academies panel called for setting up a $ 125 million US research program to study whether we could develop ways to scale up or accelerate these processes, identify environmental side effects, and figure out how to reliably measure and verify whether carbon removal is occurring. .

“Ocean geochemistry is fraught with complexity,” says Wil Burns, a visiting professor at Northwestern University who focuses on carbon removal. “We’re going to need to do a lot of iterations of this research, under very different conditions and different scales, to draw conclusions that we could do these at large scales and monetize them.”