Pulling CO2 Out of Our Oceans: Combating Climate Change Through Carbon Dioxide Removal

Jun 08 2023

Cat Kutz

Article cover image

Nearly three-quarters of our “blue planet” is covered by vast expanses of the oceans, which play a crucial role in regulating the climate and weather patterns on Earth. However, the rise of greenhouse gas emissions in the Anthropocene era have had devastating impacts on  our environment, in particular the oceans, which have directly absorbed almost 30 percent of carbon dioxide pollution.  


A growing area of research and innovation known as ocean-based carbon dioxide removal (CDR) offers the potential for both. This is one of the main focus areas of the $100M XPRIZE Carbon Removal, a competition to remove CO2 from the air or oceans and store it durably and sustainably. Many of the teams competing in the prize are developing novel approaches to removing carbon dioxide from the oceans that are explained in more detail below. 

Similar to planting trees on land, marine ecosystem restoration involves revitalizing ecosystems like mangrove forests, tidal salt marshes, and seagrass meadows to trap and store carbon. Many marine mammals and plants have the remarkable ability to store significant quantities of carbon, but according to the IUCN Red List, approximately 30 percent of marine mammal species are at risk of extinction. By addressing the issues of biodiversity loss and habitat degradation, ecosystem restoration offers a powerful avenue for ocean-based CDR. 

Seagrass in an ocean. The camera is pointed towards the surface, with sunlight being refracted in the upper right corner.

Seagrass plays a powerful role in helping trap and store carbon in our oceans. 

Another method of ocean-based CDR involves the cultivation of microalgae and macroalgae (also known as kelp and seaweed). This approach is akin to farming the sea and holds immense potential. Algae possess the ability to absorb large quantities of carbon dioxide during photosynthesis, making them an efficient carbon sink. For example, brown algae are estimated to remove up to 550 million tons of carbon dioxide per year. By expanding algae cultivation, we can enhance the ocean's capacity to capture and store carbon.

Ocean alkalinity enhancement is a fascinating method that involves adding alkaline substances, such as crushed limestone or silicate minerals, to the ocean. These substances increase the ocean's alkalinity, which aids in the absorption and storage of carbon dioxide. By manipulating the ocean's chemistry, we can effectively enhance its ability to sequester carbon. Due to the mining involved in this process, it could potentially have adverse environmental and social impacts, which new studies are taking into consideration.

Particles and gas bubbles under the surface of the ocean, with algae and seaweed covering rocks on the ocean floor through the blue water

Adding minerals that dissolve into the ocean enhances absorption and storage of carbon dioxide. 

Finally, we can take advantage of the vast depth and varying layers that compose the ocean. Deep sea storage involves injecting carbon dioxide into the deepest layers of the ocean, where it can remain sequestered for extended periods. Artificial downwelling creates vertical currents to transport surface water, rich in carbon dioxide, to the deep ocean. Artificial upwelling, conversely, transports nutrient rich water from the oceans’ depths up to the surface to stimulate the growth of phytoplankton. All of these methods enable the ocean to store carbon dioxide in its depths, preventing its release into the atmosphere.

For all of these solutions, it is imperative that they are deployed safely and equitably. There is still a great deal of work to be done by scientists, technology developers, policy makers, and local communities to ensure that these solutions are brought into the field responsibly, with careful and well considered field tests designed to showcase the efficacy and sustainability of these solutions while moderating their risks.

As we grapple with the challenges posed by climate change, it is essential that we explore innovative solutions that harness the power of the oceans. With their ability to store vast amounts of carbon dioxide, our oceans present an opportunity to remove and store carbon dioxide at significant scale. By actively pursuing these ocean-based CDR methods, and possibly others that have not yet been conceived, we can leverage the seas as a vital climate solution and work towards a more sustainable future for our blue planet.

Teams participating in XPRIZE Carbon Removal are using a variety of these methods in the competition. To learn more about ocean CDR, check out the video below.

WhaleX, a competing team from Sydney, Australia, uses a technique developed to mimic whales and their carbon-removing role in the ocean ecosystem.

Cat Kutz