The start-ups taking on climate change by extracting carbon dioxide from the sea

At the Port of Los Angeles in California, two barges filled with tanks and pipework provide an unlikely setting to open up a new frontier to tackle the climate crisis. The start-ups running them are part of a growing effort to harness the power of the ocean to capture carbon dioxide from the air.

The ocean is a massive carbon sink, having absorbed around 30% of the carbon dioxide we’ve pumped into the atmosphere. Marine life is already paying a terrible price for the resulting changes in ocean chemistry though. Carbon dioxide reacts with seawater forming carbonic acid, which in turn dissociates into bicarbonate and hydrogen ions. The more dissolved carbon dioxide, the more positively charged hydrogen ions. This results in increased acidity that in turn can dissolve the shells and skeletons of sea creatures.

Both Captura, a spin-out from the California Institute of Technology, and Equatic, from the University of California, Los Angeles, have bold plans to address climate change by removing carbon dioxide from the world’s oceans and sequestering it. They are confident that their electrochemical systems will eventually remove carbon dioxide for less than $100 (£80) a tonne. The US Department of Energy is targeting $100 a tonne for carbon removals by 2032. How quickly that milestone can be reached will depend on how fast the technology can scale and the future costs of renewable energy, but Equatic anticipates it can achieve this by 2028. For comparison, Climeworks, which has a 4000 tonne-a-year direct air capture plant running in Iceland, expects it can get costs down to around $250–$300 a tonne by the end of the decade.