• Kendall Plein

Turning Emissions into Rock: How Researchers are Looking to Scrub Carbon from the Ocean

As ocean acidification continues to worsen from escalating carbon emissions, aquatic life is struggling to adapt. Researches are now exploring one hard way to restore the oceans' natural pH — convert the excess carbon dioxide into rock.

Coastal limestone rock cliff
Credit: Unsplash/Flo P

Carbon sequestration is necessary for mitigating climate change. Although carbon emissions need to be cut, it's not enough to halt climate change. The excessive carbon must be drawn out of the air. Carbon sequestration is the process of taking carbon dioxide from the air and storing it in a carbon sink, where it can stay for an extended period. This can be natural, like planting a tree, or something much more involved, like carbon, capture, and storage (CCS) technology. The technologies range in efficiency and expense, and there is no clear winner in the atmospheric carbon sucking race.

The ocean is also a carbon sink. It can hold 150 times more carbon dioxide than air, and one-quarter of the carbon dioxide in the atmosphere is absorbed into the ocean. At first glance, this may seem like a good thing. If it weren’t for the ocean absorbing atmospheric carbon, climate change’s effects would be much more drastic. However, the dissolved carbon creates conditions for ocean acidification. If we continue to emit carbon dioxide into the atmosphere, the ocean will continue to acidify, and sea life will suffer.

Gaurav Sant, a professor and director of the Institute for Carbon Management at the University of California, Los Angeles, looks to the ocean to sequester carbon, Hakai Magazine reported. Sant’s team proposes that in taking carbon from the ocean, the water will take carbon out of the air to maintain equilibrium. Sant believes capturing carbon from seawater will be more efficient than capturing carbon from the air.

Sant’s team uses electricity to spark a reaction between the carbon dioxide, calcium and magnesium in seawater. The researchers run seawater through the electrically charged mesh, which triggers a reaction that forms carbonate rocks. The carbon, now solid rock, is stored and out of the ocean. The leftover water, without carbon, would be returned to the sea.

Sant is looking to quickly scale up this process to provide a new carbon capture method. His team is currently exploring the rate of carbon removal achievable by researching the system's efficiency, especially concerning the energy needed to run the process.

Planetary Hydrogen is another team based in Nova Scotia, looking at ocean carbon capture. Planetary Hydrogen also traps oceanic carbon into rock, but with hydroxide instead of electricity.

The ocean capture plants would not require much real estate and may require half as much energy as direct air capture. Although large quantities of rock are a byproduct of the process, Sant remains hopeful that he could use his carbonate rocks to produce carbon-neutral cement.

Alan Hatton, a chemical engineer at the Massachusetts Institute of Technology, worries that a plant using Sant’s technology may disrupt the surrounding ocean. Carbonate deposits would result that could hurt plant life and seafloor habitats. The operation of the plant may also disrupt flow patterns in the water near the plant.

Sant’s research and Planetary Hydrogen’s technologies are promising but are in the early stages of development. There is not enough data to show the scalability of these technologies or their adverse side effects. However, the carbon capture from the ocean could be a new useful tool, along with others, to mitigate the present and upcoming impacts of climate change.

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