Using bacteria to accelerate CO2 capture in oceans

Berkeley Lab researcher proposes novel scheme for capturing carbon dioxide and combating climate change

Berkeley Lab researcher Peter Agbo was awarded a grant for a carbon capture project under the Lab’s Carbon Negative Initiative. (Credit: Marilyn Sargent/Berkeley Lab)

You may be familiar with direct air capture, or DAC, in which carbon dioxide is removed from the atmosphere in an effort to slow the effects of climate change. Now a scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) has proposed a scheme for direct ocean capture. Removing COfrom the oceans will enable them to continue to do their job of absorbing excess CO2 from the atmosphere.

Experts mostly agree that combating climate change will take more than halting emissions of climate-warming gases. We must also remove the carbon dioxide and other greenhouse gases that have already been emitted, to the tune of gigatons of CO2 removed each year by 2050 in order to achieve net zero emissions. The oceans contain significantly more CO2 than the atmosphere and have been acting as an important carbon sink for our planet.

Peter Agbo is a Berkeley Lab staff scientist in the Chemical Sciences Division, with a secondary appointment in the Molecular Biophysics and Integrated Bioimaging Division. He was awarded a grant through Berkeley Lab’s Carbon Negative Initiative, which is aiming to develop breakthrough negative emissions technologies, for his ocean capture proposal. His co-investigators on this project are Steven Singer at the Joint BioEnergy Institute and Ruchira Chatterjee, a scientist in the Molecular Biophysics and Integrated Bioimaging Division of Berkeley Lab.

Q. Can you explain how you envision your technology to work?

What I’m essentially trying to do is convert CO2 to limestone, and one way to do this is to use seawater. The reason you can do this is because limestone is composed of magnesium, or what’s called magnesium and calcium carbonates. There’s a lot of magnesium and calcium naturally resident in seawater. So if you have free CO2 floating around in seawater, along with that magnesium and calcium, it will naturally form limestone to a certain extent, but the process is very slow – borderline geologic time scales.

It turns out that the bottleneck in the conversion of CO2 to these magnesium and calcium carbonates in seawater is a process that is naturally catalyzed by an enzyme called carbonic anhydrase. It’s not important to know the enzyme name; it’s just important to know that when you add carbonic anhydrase to this seawater mixture, you can basically accelerate the conversion of CO2 to these limestones under suitable conditions.

And so the idea is to scale this up – drawing CO2 out of the atmosphere into the ocean and ultimately into some limestone product that you could sequester.

Julie Chao, Berkeley Lab, 16 May 2022. Full article.

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