Scientists are tricking oceans into absorbing more CO2 for us

Efforts to remove carbon dioxide (CO2) from the atmosphere have gained momentum in recent years, with innovative strategies emerging to complement land-based approaches like direct air capture. Iceland, known for pioneering climate solutions, is now the site of new marine carbon dioxide removal (mCDR) techniques, including the dumping of wood waste into the ocean to stimulate carbon sequestration. These strategies aim to enhance the natural ability of oceans to absorb CO2, which already soak up about 30% of all emissions, far surpassing the atmosphere's capacity.

For billions of years, the ocean has played a critical role in regulating atmospheric CO2, converting it into various carbon forms that circulate via currents or settle on the seafloor. The Yale School of Environment has shined the spotlight on a new mCDR method which aims to amplify this natural process. A U.S.-based company, Running Tide, is testing the use of timber industry wood waste in Icelandic waters which is otherwise often sold as feedstock to be burned for bioenergy or simply left to rot. This, in turn, usually releases the wood’s stored carbon back into the air. Running Tide coats the wood chips with alkaline material, seeking to combat this process by transfering CO2 to the ocean and mitigate acidification simultaneously.

The Intergovernmental Panel on Climate Change (IPCC) underscores the need for carbon dioxide removal (CDR) to meet global climate goals. It estimates that removing up to 15 gigatons of carbon annually may be necessary to limit warming to 1.5–2°C, a threshold critical for avoiding catastrophic ecological and social impacts. Achieving this requires a diverse “tool bag” of solutions, according to experts like Nicholas Ward from the Pacific Northwest National Laboratory (PNNL), who advocates for deploying multiple smaller-scale solutions to collectively meet this target.

Running Tide are not the only active player in the field of mCDR research. A wide range of other marine techniques are being explored globally:

1. Kelp and Algae Cultivation: Some companies grow aquatic plants that absorb CO2 and then sink them to the deep ocean or bury them on land.

2. Ocean Alkalinity Enhancement (OAE): This approach reduces seawater acidity to increase its CO2 absorption capacity. Companies like Ebb Carbon use electrodialysis to extract acid from seawater, raising its alkalinity. Ebb Carbon's process, operational at PNNL's Sequim campus, has also been applied to brine from desalination plants, which produce 40 billion gallons of brine daily. If converted to alkalinity, this brine could sequester over 1 billion tons of CO2 annually.

3. Enhanced Rock Weathering: Alkaline rocks like basalt or olivine are mined, pulverized, and added to oceans to accelerate natural processes that sequester carbon over thousands of years. Proponents argue that such “open systems,” leveraging Earth's natural carbon cycle, offer scalable and cost-effective solutions compared to closed systems like direct air capture.

4. Electrodialysis Systems: Companies are also developing filtration systems that boost water’s carbon sequestration ability while addressing acidification, a harmful byproduct of excess CO2.

Marine carbon removal is a form of geoengineering, a polarizing concept in climate science. While atmospheric geoengineering, such as altering the sky's reflective capacity with sulfur dioxide injections, draws significant criticism, mCDR faces skepticism primarily due to limited understanding of its impacts. However, Iceland’s proactive stance and the urgency of the climate crisis make it an ideal testing ground for these experimental technologies.

Governments are beginning to recognize the potential of mCDR. The U.S. Department of Energy’s ARPA-E program, for instance, launched the SEA-CO2 initiative to enhance monitoring and measurement technologies for oceanic carbon storage. The program recently allocated $36 million to 11 labs, academic institutions, and private companies, including PNNL, to refine OAE and other mCDR techniques.

Scaling mCDR to gigaton levels requires addressing technical, ecological, and regulatory challenges. Advocates like Matthew Eisaman, cofounder of Ebb Carbon, emphasize the potential of “open systems” that integrate seamlessly with Earth’s carbon cycle, offering scalable, low-cost solutions. Iceland’s experiments, supported by international efforts, underscore the importance of diversifying CDR approaches to tackle the climate crisis effectively.

By Nazrin Sadigova