Chemistry-based techniques to capture and store ocean carbon could be part of the solution to our warming climate, according to a group of scientists.
The ocean holds onto about 16 times as much carbon as all of the plants and soil on dry land, according to the World Ocean Review. For instance, experts estimate that seagrass provides about $88.3 billion worth of carbon storage each year.
However, those waters can only hold so much, and excess carbon acidifies the ocean, putting ecosystems and animals at risk, according to Tech Xplore.
That's why a team of researchers recently investigated techniques to capture and store this gas. These included natural methods like sinking carbon-storing seaweed to the bottom of the ocean, which, though economical, has risks like endangering wildlife.
The scientists also analyzed three electrochemical methods, which use electricity and specialized membranes or fine filters to separate seawater into acidic or basic solutions.
While more expensive than other solutions, chemistry-based technologies could help us remove 10 billion tons of this greenhouse gas each year.
Acid-stripping carbon dioxide converts ocean-based carbon into bubbling gas, which can be caught and used to make fuel. The initial chemical reaction turns the ocean water acidic, but the process also produces a basic liquid as a byproduct — this can be returned to the water to balance its pH.
Another electrochemical method helps get rid of some of the excess acid that our oceans store — scientists inject a basic solution directly into seawater to reduce its acidity. A third method transforms the ocean's carbon into carbonate, a chalky substance that can be used in building construction.
The second two techniques permanently remove carbon (the first just captures it), but they also produce a lot of acid that would need to be safely disposed of, according to the researchers.
The team also looked into ways in which these techniques could store the carbon for hundreds — or even thousands — of years. One such strategy would have companies submerging liquid carbon dioxide deep into the ocean, creating liquid carbon lakes. However, this could trap and kill any wildlife located beneath the lake during its formation. That's one reason the scientists encourage more research on the topic.
One other caveat: Ocean carbon removal techniques all require substantial energy to operate. Wave and offshore wind energy could help power future projects, and fields of marine energy and marine carbon removal could form mutually beneficial partnerships, according to the scientists.
"I'm just trying to get people interested in trying this," James Niffenegger, one of the researchers, told Tech Xplore. "There's a lot of potential opportunities for collaborating between these two fields."
Meanwhile, other companies are working on carbon capture and sequestration on land. An Icelandic startup called Carbfix is injecting carbon dioxide mixed with groundwater into basalt rock, condensing a process that normally takes thousands of years into just two.
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