Ocean-based carbon dioxide removal technology is ramping up, with startups and existing companies racing to develop electrochemical techniques that either remove carbon from seawater or prompt oceans to suck up more. Electrochemical marine carbon dioxide removal (mCDR) aims to store carbon in the ocean or strip it from seawater using electricity. Broadly speaking, mCDR is divided into two methods with some overlap: ocean alkalinity enhancement (OAE) and direct ocean capture (DOC), also known as direct ocean removal. OAE electrochemically splits seawater into a base and acid stream. The base stream is added back to the ocean, notching up pH to make the ocean’s surface more alkaline, prompting more CO2 to be absorbed from the atmosphere over time in the form of bicarbonate. The acidic stream can be used by industry or sequestered in the deep sea. “If you think of the ocean like a sponge, adding alkalinity makes that sponge bigger, so it’s able to take up more carbon dioxide,” says Helen Findlay at the Plymouth Marine Laboratory. DOC also uses electrochemical processes to strip carbon dioxide from seawater. One method converts dissolved inorganic carbon within seawater into a gas that is then captured. Low CO2 water is returned to the ocean, where it naturally rebalances as carbon dioxide is drawn down from the atmosphere. The captured carbon can be stored geologically or used in industrial processes, much like direct air capture on land. “Back to the sponge analogy, direct ocean capture is like squeezing the sponge and then allowing…This article was originally published on Mongabay
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