Should We Use the Ocean to Capture Carbon?

Even as world leaders convene in Azerbaijan for COP29 to chart a path forward to avoid a climate catastrophe, the fact is that the world has waited too long for emissions reduction alone to solve the climate crisis. 

Climate change is here, and nowhere is this more immediately apparent than in our ocean. In the last year alone, we’ve seen historic marine heatwaves, intense hurricanes fueled by warming waters, and a generational coral-bleaching event. 

It makes sense that our ocean would bear the most immediate impacts because it is on the front line of actually absorbing and storing the carbon that causes climate change to begin with. Since the beginning of the Industrial Revolution, the ocean has absorbed about 31% of manmade CO₂ emissions. On a yearly basis, that’s more than the global emissions from the largest greenhouse gas-emitting sector, electricity and heat production. 

What if we could harness the power of the ocean to store enough carbon, more than it already is, and buy us more time to meet our emission-reduction goals? This is a question that more and more scientists, policymakers and entrepreneurs are asking. The growing field of marine carbon dioxide removal (mCDR) is exploring ways that we can augment the ocean’s ability to absorb and store the most prolific greenhouse gas warming our atmosphere. 

But not all mCDR is created equal. There are a variety of methods proposed, and they differ in their potential to be effective at storing carbon and the potential impacts that might result. Any amount of engineering in the ocean has risks, and we cannot afford to trade one problem for another: mCDR that significantly harms the ocean, and its biodiversity would only set us back in our goals of tackling climate change. 

Researchers are still evaluating mCDR methodologies to understand how much carbon they can draw down from the atmosphere, how long the ocean will store planet-warming emissions and what benefits or negative effects various methods may have on ecosystems and communities that depend on the ocean. For example, ocean alkalinity enhancement—a proposed form of mCDR that involves adding alkaline substances to the ocean to increase the ocean’s natural ability to absorb CO₂ from the air—has the potential to sequester as much as 15 gigatons of CO₂ a year. That’s slightly less than half of the world’s total CO₂ emissions. But it would also require extensive mining and processing of raw materials on land, which raises local environmental and health concerns and has unknown consequences for the pH and the natural carbon cycle of the ocean. 

Insert quote block: “We need to make sure that marine carbon dioxide removal (mCDR) does not turn into an unregulated, unverifiable boondoggle” – Anna-Marie Laura

With so many unknowns and the clock running down to address the climate crisis, we need to know which mCDR methods might work, and at the same time, we need to make sure that mCDR does not turn into an unregulated, unverifiable boondoggle. Last year, the White House Office of Science and Technology Policy recognized the urgency of the need for policy and research guidance and announced a Fast-Track Action Committee tasked with evaluating the merits of and concerns about different types of marine CO₂ removal and developing relevant guidelines for research.

Federal oversight, coordination and scientific support are critical to ensuring mCDR projects are effective and safe. At this early stage, government involvement is especially needed to provide the monitoring, reporting and verification all parties desire to ensure any mCDR approach is not simply a greenwashing exercise. With mCDR investors and practitioners eyeing the carbon market to make projects profitable, federal oversight can ensure that the public doesn’t shoulder the long-term social and environmental impacts while private companies capture the financial benefits. 

Last week, the White House’s Fast Track Action Committee on Marine Carbon Dioxide Removal released a report outlining a national research strategy for mCDR that charts a path toward responsible mCDR research to guide future decision-making. In the past, Ocean Conservancy has helped draft a code of conduct for mCDR research to set baselines for environmental practices and social consent, so we were glad to see the report recommend that federal agencies consider how adherence to one and other safeguards should be a part of requirements to receive federal funds . In particular, the FTAC strategy emphasizes the need to involve Tribal and Indigenous groups, local communities and ocean users who might be affected by the projects early and often during all project phases. Participation by relevant groups will be crucial to ensuring projects are operated in an environmentally responsible and just manner. It also recommended that an interagency working group be formed so the federal government can provide consistent and coordinated guidance on all these future endeavors, including a prioritization of research on the most promising mCDR approaches. The guidance laid out in the report should serve as a roadmap for federal agencies, and Congress should provide comprehensive legislation to execute and properly fund this work. 

Some additional areas that should be considered as responsible mCDR research advances are offramps for methods as we learn more about effectiveness or potential impacts. It’s unlikely that all mCDR methods will be similarly effective, so parameters or criteria for how to determine which methods should continue to be researched and which should be deprioritized will be important in the future. We cannot afford to invest endlessly in solutions with little potential when climate finance and investment is already limited.

Tackling climate change is the number one action we can take to protect our ocean, and we need to understand if and how mCDR can be a part of the solution set. Implementation of the national mCDR strategy will make sure the research to help us answer those questions is done responsibly. For the sake of our ocean and all the communities that depend on it, we cannot afford to trade one existential threat for another. Join Ocean Conservancy in our effort to ensure that mCDR research is conducted responsibly.