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Scientists extract carbon dioxide from the ocean by turning it to rock

Human-induced climate change is one of the most prevalent threats we are facing as a species, and to combat this, we must change our way of living and innovate new solutions to temper the damage that has already been done.

For instance, carbon emissions in the atmosphere need to be reduced at a much faster rate than nature allows. For every ton of carbon dioxide, we pump into the air, approximately a quarter of it gets absorbed by the ocean like a sponge. The excess carbon dioxide present in these bodies of water acidifies it and threatens biodiversity.

Most of the efforts to pull carbon dioxide from the environment focus on pulling the gas directly from the atmosphere, which has proven to be challenging and expensive. In contrast, Gaurav Sant, a civil and environmental engineering professor and director of the Institute for Carbon Management at the University of California, Los Angeles, is leading a team that is researching new, innovative ways to more efficiently extract CO2 from the environment.

Large bodies of water, like oceans, hold more than 150 times more carbon dioxide than the air. Instead of focusing on extracting gas from the air, Sant and his colleagues propose removing carbon from the ocean, allowing the ocean to absorb more gas from the atmosphere to maintain the balance. How do they want to do this? By turning the carbon extracted from the ocean into rock.

There is a lot of calcium and magnesium present in seawater, and when calcium and magnesium ions combine with carbon dioxide, they form calcite or magnesite. This is how many marine organisms build their shells. Sant and his team figured out how to trigger a similar chemical reaction quickly and efficiently by jolting the water with electricity. The team has developed a new technology that will run seawater through an electrically charged mesh, using electrolysis to spark the required chemical reactions to make carbonate rocks.

Right now, the team has constructed a small prototype that they flood with simulated seawater to demonstrate the concept and to study how much carbon dioxide can be removed over varying periods of time. They will also be using the model to determine which operational variables would impact the process — a “formative step towards building larger systems and proving the process at a larger scale.”

The proposed facility for this process would look like a water treatment plant, but instead of sifting impurities out of the water, the systems would use electricity to force carbon, calcium, and magnesium to react and become solids. The carbon-free water would then get put back into the ocean.

A wonderful side effect of returning the water to the ocean is that what gets returned is actually a bit more alkaline than what was extracted. This more alkaline water may mitigate the effects of ocean acidification in its immediate vicinity.

Another useful byproduct of Sant’s electrolysis method is hydrogen gas. According to Sant, even if the entire facility were powered by natural gas rather than renewable energy, the entire process could still be carbon negative simply because of the hydrogen gas byproduct.

The concept is still in its early stages of development, and there are a lot of potential issues that the team may have to face. For example, there should be a plan for the carbon-neutral limestone that is produced through this method of carbon capture. Also, how will the process affect marine ecosystems in the real world? The team realizes that despite the enormous potential of their innovative idea, there are likely to be unintended and unknown consequences. Still, Sant hopes that their work will inspire others to investigate carbon capture and its immense potential to positively impact the fight against climate change.

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