Carbon dioxide in oceans is a hazard to the environment, but a new technique to sequester the gas has been developed that produces super-clean hydrogen fuel as a by-product.

Lawrence Livermore National Laboratory researchers developed the new method that removes carbon dioxide from water and stores the gas as environmentally friendly seawater bicarbonate. This transforms carbon dioxide gas from a substance dangerous to the environment into one that will help repair damage to coral reefs and other marine life.

"[S]uch systems at scale might provide a relatively efficient, high-capacity means to consume and store excess atmospheric CO2 as environmentally beneficial seawater bicarbonate or carbonate," Greg Rau of UC-Santa Cruz, lead author of the article on the findings, said. "But the process also would produce a carbon-negative 'super green' fuel or chemical feedstock in the form of hydrogen."

The National Oceanic and Atmospheric Administration (NOAA) estimates that oceans take up about 25% of the carbon dioxide that humans put in the air. When that CO2 dissolves in water, it forms carbonic acid. As the amount of CO2 in the air increases, so does the amount of carbonic acid and gas dissolved in the Earth's waters, which can prove dangerous to marine life.

The new process uses electrolysis to create a solution from salt water that absorbs much larger quantities of carbon dioxide than ocean water alone. Carbonate and bicarbonates similar to soda ash and baking soda are produced by this method. By returning the salt water, now in the form of bicarbonate solution, to the ocean, it could help lower the acidity of treated water bodies, benefiting marine life. The chemical reactions that help stabilize the acidity of seawater in this scenario - carbonic acid and bicarbonates - are the same ones that moderate the acidity of your blood.

Now tested successfully in the laboratory, field tests still remain. This new method of carbon sequestration is less expensive than chemical methods, making it more economical for long-term use.

"Our process avoids most of these [price] issues by not requiring CO2 to be concentrated from air and stored in a molecular form, pointing the way to more cost-effective, environmentally beneficial, and safer air CO2 management with added benefits of renewable hydrogen fuel production and ocean alkalinity," Rau said.