Researchers now more than ever are delving deeper into the ability of the ocean to remove and sequester CO2 from the air and are trying to amplify it. They are examining the possibility of artificially redistributing surface acidity in the oceans by making use of sedimentary carbonates naturally found on the ocean floor.
The process involves just seawater and energy. The energy could be in the form of an open-ocean power source that runs on waves, wind, or ocean thermal energy. The energy could be used to electrochemically split seawater into acid and base. The acid would be pumped into the deep ocean and the base would go to the surface to enable pH stabilization and maintain the flux of CO2 from the atmosphere.
Releasing the acid in the deep ocean would encourage the dissolution of carbonate sediments, which would produce HCO3⁻ ions. They would eventually circulate to the ocean’s surface and promote CO2 uptake from the atmosphere.
The HCO3⁻ ions react with the atmospheric CO2 at the surface to form calcium carbonates that end up at the bottom of the ocean and lock away the CO2 they capture from the air.
According to simulations, up to 3 gigatons of carbon could be removed annually over 50 years, with the surface water becoming more alkaline and the pH of deepwater increasing by no more than 0.2.
“While the deep ocean becomes more acidic in their model, the surface ocean pH increases, which may be good news for surface dwelling organisms and ecosystems sensitive to ocean acidification,” comments Phil Renforth, an engineer and geochemist at Heriot-Watt University in the UK.
Researchers also have estimated a minimum cost per ton of CO2 captured of $93 – $297 (£67 – £218) via this method – still lower than costs of other CO2 removal strategies like CO2 extraction ($373 – $604), direct air capture ($89 – $506) and terrestrial weathering ($24 – $578).
Another team of scientists is also looking into the ability of the ocean to remove and store CO2 and have founded a startup called Seachange. A technology – machine pulling in water from the ocean, is used to essentially speed up the natural CO2 sequestration into minerals.
Natural carbon sink methods like the ones proposed above, enhanced by technology are a concept that attracts a lot of attention. They also make the world reconsider our relationship with the ocean and come up with ways how it could be harnessed to mitigate climate change.