In Halifax, Nova Scotia, efforts to combat global warming are expanding with innovative solutions leveraging the ocean’s capabilities. The idea focuses on using the ocean’s vast capacity to absorb carbon dioxide, potentially mitigating climate change. Numerous companies and academic groups are testing methods like submerging rocks, nutrients, crop waste, or seaweed into the ocean to trap carbon for centuries. Over the past four years, nearly 50 field trials have been conducted, while startups have accrued substantial investment funds. However, there remains a significant debate about the potential repercussions on ocean ecosystems if these strategies were implemented extensively and about the true climate benefits they provide. Critics warn that the pace of development is too rapid, with insufficient regulatory oversight.
Current climate models indicate that merely reducing emissions will not suffice to combat global warming, implicating the need to actively remove carbon dioxide from the atmosphere. On land, strategies such as carbon capture, underground storage, and reforestation are underway but face spatial limitations and potentially affect nearby communities. The ocean, with its inherent ability to absorb heat and carbon, presents a seemingly boundless opportunity. Adam Subhas from the Woods Hole Oceanographic Institution in Massachusetts questions whether utilizing the ocean’s vast surface could help mitigate severe climate change impacts.
Ocean-centered climate initiatives primarily aim to decrease or transform the ocean’s carbon dioxide content. Will Burt, Planetary Technologies’ chief ocean scientist, explains that successful implementation could make the oceans act “like a vacuum,” absorbing more atmospheric gases. Planetary’s approach involves using magnesium oxide to convert carbon dioxide into stable molecules when dissolved in seawater. Similarly, limestone, olivine, and other alkaline rocks are capable of this transformation. Alternative methods include cultivating seaweed and algae to absorb oceanic carbon dioxide similarly to how forests sequester atmospheric carbon. Some strategies even propose utilizing deep-sea areas to sequester organic material that would otherwise emit greenhouse gases on land.
These ventures are largely financed through the sale of carbon credits, representing one metric ton of carbon dioxide removed from the environment. Although widely debated and largely unregulated, carbon credits have gained popularity as a way for companies to seemingly offset emissions. In the past year, the industry sold over 340,000 marine carbon credits, a dramatic increase from 2,000 credits four years prior. While notable, this amount falls far short of the carbon removal volume needed to maintain a habitable planet.
Community response has been mixed, especially among coastal populations. For instance, a project near Duck, North Carolina, aimed to deposit shiploads of olivine but faced enough public concerns to significantly reduce its scale. Fisheries and local communities have also shown resistance to related ocean projects. Sara Nawaz of American University’s Institute for Responsible Carbon Removal acknowledges the challenge scientists face in gaining public support, citing general skepticism towards climate engineering.
The oceanic environment is inherently challenging, with complex interactions affecting the success of carbon strategies. The potential for added materials to either sink, disperse, or migrate complicates tracking and monitoring efforts. Dalhousie University’s Katja Fennel notes the limitations of measurement capabilities in assessing how much carbon is captured. Uncertainty also persists regarding the longevity of carbon storage, especially concerning biodegradable materials like algae or wood chips, which may decompose and release carbon back into the atmosphere. Even proven solutions, when scaled, require immense resources and infrastructure to meet desired climate objectives.
Scaling up to deal effectively with billions of tons of emissions annually raises numerous logistical questions. David Ho of the University of Hawaii suggests considering the consequences of expansion on such a scale. A potential future imagined by Planetary’s Burt involves global shoreline infrastructure for mineral pumping, demanding consistent magnesium oxide supply and energy-intensive processes. Meanwhile, seaweed and algae farming would require an exponential increase. Estimates by the National Academies of Sciences, Engineering, and Medicine suggest that substantial global coastline coverage by kelp would be necessary to make significant progress. Seafields, a company active in the Caribbean, envisions an extensive Sargassum farm spanning over 200 miles between Brazil and West Africa.
These expansions carry risks of unseen environmental damage that small-scale efforts might not reveal, but global ocean currents could propagate such effects worldwide. Nonetheless, some argue that the risk of not attempting to find solutions far outweighs these concerns, as uncontrolled climate change remains the alternative.
