Hawaii Startup Launches World’s First Ocean-Assisted Carbon Removal Plant

While most are aware that the ocean has borne the brunt of our climate crisis, few know how greenhouse gasses specifically pose a danger to marine life. The ocean—specifically a layer of the ocean called the twilight zone—absorbs approximately 6 billion metric tons of carbon every year, helping to decrease the negative effects of carbon pollution in our atmosphere. But this absorption comes at a cost: all that extra carbon results in ocean acidification, which limits coral growth, wears down crustaceans’ exoskeletons, and kills off plankton, among other things. There also might be a limit to how much carbon the ocean can absorb, leaving us with one less mitigation method (if you can call it that) as we learn to effectively manage climate change.

Heimdal, a startup founded by two Oxford University graduates, seeks to buy us time by giving the ocean a carbon-capturing restart. Heimdal’s plant uses reverse osmosis (a filtration method used in some drinking water systems) to desalinate batches of saltwater brine. After that, an electrochemical cell performs a process called electrolysis, in which hydrochloric acid is removed from the brine via molecular rearrangement. The desalinated solution can then be returned to the ocean, helping to locally neutralize the water’s pH. The removal of excess acidity also allows the seawater to begin capturing carbon all over again.

While “direct air capture” organizations operate machines that chemically pull carbon out of the atmosphere, Heimdal co-CEO Erik Millar tells FastCompany there are benefits to focusing on the ocean. Thanks to the rapid absorption described above, seawater contains more carbon than the air. Ocean-assisted carbon removal also requires less energy and space than direct air capture facilities, making the process much cheaper and easier to scale than its slightly more conventional alternative.

Heimdal can offset the costs of its method by selling its byproducts, too. The hydrochloric acid produced during the electrolysis stage of Heimdal’s process can be sold to textile, battery, metal, and even food manufacturing facilities. This reduces the startup’s already-low cost of carbon removal, which sits at about $475 per ton.

As the climate crisis becomes more severe, Heimdal is focused on expanding its number of facilities. Millar has high hopes for the company: “We’re projecting that we’re going to be capturing five million tons per year within three years,” he told FastCompany.