Another Ocean Climate Solution Attempted by California Researchers - Slashdot

The Associated Press visited a 100-foot barge moored in Los Angeles where engineers built "a kind of floating laboratory to answer a simple question: Is there a way to cleanse seawater of carbon dioxide and then return it to the ocean so it can suck more of the greenhouse gas out of the atmosphere to slow global warming?"

The technology, dubbed SeaChange, developed by the University of California Los Angeles engineering faculty, is meant to seize on the ocean's natural abilities, said Gaurav Sant, director of UCLA's Institute for Carbon Management. The process sends an electrical charge through seawater flowing through tanks on the barge. That then sets off a series of chemical reactions that trap the greenhouse gas into a solid mineral that includes calcium carbonate — the same thing seashells are made of. The seawater is then returned to the ocean and can pull more carbon dioxide out of the air. The calcium carbonate settles to the sea floor.

Plans are now underway to scale up the idea with another demonstration site starting this month in Singapore. Data collected there and at the Port of Los Angeles will help in the design of larger test plants. Those facilities are expected to be running by 2025 and be able to remove thousands of tons of CO2 per year. If they are successful, the plan is to build commercial facilities to remove millions of tons of carbon annually, Sant said...

Scientists estimate at least 10 billion metric tons of carbon will need to be removed from the air annually beginning in 2050, and the pace will need to continue over the next century... According to the UCLA team, at least 1,800 industrial-scale facilities would be needed to capture 10 billion tons of atmospheric carbon dioxide per year, but fewer could still make a dent.
The article notes alternate ideas from other researchers — including minerals on beaches that increase the ocean's alkalinity so it can absorb more carbon dioxide.

But this SeaChange process also produces hydrogen. So the director of UCLA's Carbon Management institute also founded a startup that generates revenue from that hydrogen (and from "carbon credits" sold to other companies) — hoping to lower the cost of removing atmospheric carbon to below $100 per metric ton.