Path to Zero
Path to Zero
3.04 - Ocean-Based Carbon Removal with Northwestern University’s Dr. Wil Burns

Developing methods to enhance ocean-based carbon dioxide removal is one of the topics Tucker explores with an expert who has been studying climate change for more than 30 years.

Dr. Wil Burns is a visiting professor at Northwestern University’s Environmental Policy and Culture Program and emeritus co-founding director of the Institute for Carbon Removal Law & Policy at American University. He also served as the Director of the Energy Policy & Climate program at Johns Hopkins University in Washington, DC.

The role oceans play in absorbing carbon

The oceans cover more than 70% of the Earth’s surface and play a crucial role in taking up CO₂ from the atmosphere. Scientists believe that the oceans currently absorb 30-50% of the CO₂ produced by the burning of fossil fuel.

Tucker asks Dr. Burns about the potential for the oceans to absorb even more carbon.

Burns emphasizes that scientists are in the early stages of evaluating carbon removal approaches and in addition to looking at the potential, it’s important to evaluate the risks.

“These are very sensitive ecosystems,” says Burns. “We know less about the world’s oceans than we know about the moon, so we have to be very careful. If we’re going to be engaged in large scale interventions trying to protect the climate, we potentially could wreak havoc with the oceans.”

Ocean-based Ways to Remove CO2 from the Atmosphere

The first ocean-based carbon removal method Dr. Burns discussed is a chemical approach known as ocean alkalinization. It involves adding alkaline substances to seawater to enhance the ocean’s natural carbon sink. These substances could include minerals, such as olivine, or artificial substances, such as lime or industrial byproducts. Adding alkalinity to the ocean removes carbon from the atmosphere through a series of reactions.

Burns says there are scientists that are making proposals to do experiments with ocean alkalinization and some believe the method has the potential to remove a significant amount of CO₂ from the atmosphere.

“We don’t know about the risks yet of doing this and some are worried about releases of heavy metals associated with some of these minerals,” says Burns. He also points out this method might involve a substantial increase in mining operations, which could reduce the CO₂ benefits.

Another carbon removal method that is further along is kelp farming. Burns says there are a couple of companies that have started doing this, including Running Tide, based in Maine. Running Tide captures CO₂ using kelp microforests. As the microforests float, the kelp grows and absorbs CO₂. In a matter of months, growth will peak and the microforest sinks deep to the ocean floor where it is either buried in sediments or consumed by deep-sea marine life.

“It’s an approach being looked at in earnest and receiving quite a bit of funding,” says Burns. “We don’t know ultimately how much of the CO₂ is sequestered for the long term in the sediments and we don’t know if there are negative impacts of creating huge amounts of additional biomass.”