Ocean-based experiments for carbon removal are on the rise, but remain controversial
As part of The World’s ongoing series The Big Fix, Host Carolyn Beeler speaks with Susanna Lidström, a researcher at the KTH Royal Institute of Technology in Stockholm, Sweden, about the tension between the swell of interest in marine geoengineering and the lack of scientific consensus about its role as a climate solution.
Marine geoengineering projects are on the rise: In Nova Scotia, one start-up is pumping a bright pink slurry of magnesium oxide into the ocean. Off the coast of North Carolina, another company deposited enough olivine-rich sand to fill two Olympic-sized swimming pools. And in Singapore, a company plans to suck up sea water and run electric currents through it.
Dozens of projects have launched in the last few years — all aiming to increase the ocean’s capacity to store carbon dioxide.
“The ocean is so vast, and the volumes of water [are] so big that the ocean can hold a lot more carbon dioxide than the atmosphere,” said Susanna Lidström, a researcher at KTH Royal Institute of Technology in Stockholm, Sweden and the Scripps Institute of Oceanography. “The idea is to enhance the ocean’s ability to take up [more] carbon dioxide, and thereby lower the levels of carbon in the atmosphere.”
But the idea of experimenting with the ocean is highly controversial, especially as the technologies have not been proven at scale. As part of The World’s ongoing series The Big Fix, Host Carolyn Beeler spoke with Lidström about the tension between the swell of interest in marine geoengineering and the lack of scientific consensus about its role as a climate solution.
Carolyn Beeler: What are the major kinds of projects we are seeing that are being tested around the world right now?
Susanna Lidström: There are a few different approaches. One is that you add material to the ocean that increases the ocean’s production of organic matter. You can do this through adding iron to the ocean, or you can add other alkaline materials that increase the ocean’s uptake of carbon. You can also sink organic matter, [which] you take either from the ocean in the form of algae, or from land such as wood chips, and you just sink all this matter to the bottom of the ocean. You can also extract carbon directly from the seawater through chemical processes. Then, [you] pair [all this] with this idea that it will be possible to then store the carbon that you collect at the bottom of the ocean.
How much evidence is there that that actually works?
It’s hard to say exactly, because you can demonstrate a chemical reaction that works. You can do this. But none of these technologies have been demonstrated at scale. Once you move to scale, there are so many “unknown unknowns,” so to speak. If you sink a lot of organic matter to the seafloor, you will smother all the life that lives there. If you add a lot of particles to the water column, that will affect all the organisms that live there. In the worst-case scenario, you will disturb the existing cycles that take up carbon from the atmosphere and store it in the ocean. But then there are a lot of social concerns, as well, when the people driving these ideas are basically private actors who are looking to benefit. There’s no governance of these activities. There’s also no mechanism to monitor what’s going on. There is a high risk that you do experiments in a place where the local and regional environment and the people who live there may suffer from impacts on fisheries and other things.
There are a lot of concerns even if these projects could be scaled up to an effective size. But lots of new projects are being launched. Some governments are backing experiments into this approach. Carbon credits are already financing some of these projects. And there’s money from accelerators and things like that. So, why is there this big interest in this idea right now if it is still in it’s very early stages and has yet [been] unproven?
I think the main reason is people are getting increasingly desperate, as we’re failing to lower emissions significantly. People are looking for other ways to address the climate crisis. But I think if you take a more holistic view of all the other environmental crises that are ongoing as well — like biodiversity loss and the state of the ocean — the argument for marine carbon dioxide removal becomes much weaker.
Are there scientists who don’t have an active stake in one of these companies doing this that would disagree with what you just said? That we have not reduced carbon emissions, and so, we need to explore other possibilities for removing carbon from the atmosphere?
Yes, I mean, scientists are just people and they have a lot of different opinions about this. I wouldn’t say that there’s any consensus among the scientific community. People have a lot of different opinions. But I think the one thing that most scientists would agree on is that a lot more research is needed and a lot more governance frameworks are needed.
What would it take for this to become a meaningful climate solution? What would it take for you to be convinced that this could be, or has become, a meaningful climate solution?
One of my main concerns at the moment is that not much is said about the final storing of the carbon. Often it’s just added as a footnote or something that says “we will then store this in the deep ocean,” as if that’s a place that you can just store things and that doesn’t have life. So … where is it going to go? The estimates are that you can store this carbon [for] as little as 50 years. And I mean, if we can’t store it for a longer time than that, it’s just not meaningful.
This interview has been lightly edited for clarity.
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