Startups aim to curb climate change by pulling carbon dioxide from the ocean—not the air

https://www.science.org/content/article/startups-aim-curb-climate-change-pulling-carbon-dioxide-ocean-not-air

By ROBERT F. SERVICE, Science. 

Excerpt: ...one long gray barge docked at the [Port of Los Angeles] is doing its part to combat climate change. On the barge, which belongs to Captura, a Los Angeles–based startup, is a system of pipes, pumps, and containers that ingests seawater and sucks out CO₂, which can be used to make plastics and fuels or buried. The decarbonated seawater is returned to the ocean, where it absorbs more CO₂ from the atmosphere, in a small strike against the inexorable rise of the greenhouse gas. After a yearlong experiment with the barge, which is designed to capture 100 tons of CO₂ per year, Captura is planning to open a 1000-ton-per-year facility later this year in Norway that will bury the captured CO₂ in rock formations under the North Sea. Equatic, another Los Angeles–based startup, is launching an even larger 3650-ton-per-year ocean CO₂ capture plant this year in Singapore, and other companies are planning demos as well. ...Proponents say capturing CO₂ from the ocean should be easier and cheaper than a seemingly more direct approach: snagging it directly from the air. Direct air capture, which relies on fans to sweep air past absorbent chemicals, currently costs between $600 to $1000 per ton of CO₂ removed, largely because atmospheric CO₂ is so dilute, making up less than 0.05% of the air by volume. Earth’s oceans, in contrast, hold the gas at a concentration nearly 150 times higher, and absorb roughly 30% of all CO₂ emissions each year....