Hold Your Sargassum: Seaweed is No Joke When it Comes to Carbon Capture
Seaweed may be known for sometimes tangling up swimmers along coastlines, but clearly its real-world secret power is capturing carbon.
Nonprofit group Oceans 2050 has released a new study highlighting the potentially significant climate mitigation benefits in seaweed farming. Oceans 2050, co-founded by environmental filmmaker Alexandra Cousteau and Chief Scientist Carlos Duarte, published its findings in Nature Climate Change.
The study, titled “Carbon burial in sediments below seaweed farms matches that of Blue Carbon habitats,” marks the assessment of carbon burial rates beneath seaweed farms globally. The study, conducted across 20 seaweed farms covering five continents, confirmed that seaweed farming has the potential to sequester carbon in the sediments below at rates comparable to vegetated coastal ecosystems like mangroves, salt marshes, and seagrasses.
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“This research provides compelling evidence of the critical role that seaweed farming can play in addressing the climate crisis,” Alexandra Cousteau, French environmentalist, president of Oceans 2050 and granddaughter of oceanographer and filmmaker Jacques-Yves Cousteau, said in a statement. “By quantifying its carbon sequestration potential, we hope to unlock new avenues for investment in sustainable aquaculture as a climate solution.”
The study touted that the “dual benefits” of seaweed farming includes food security and climate change mitigation. Many types of seaweeds are consumed as food.
Among the key environmental findings in the Oceans 2050 study include that seaweed farms bury carbon at rates similar to mangroves and seagrasses, which are known for their climate benefits. The older and larger the seaweed farm, the more carbon it can store, according to the report.
A 2022 Environmental Defense Fund report on carbon sequestration by natural seaweed stands quoted earlier data that dissolved carbon removed by seaweed is slowly replaced by atmospheric CO2 resulting in a migration from carbon from the air into the ocean. Different types of seaweed process carbon differently, such as calcifying algae which releases a molecule of CO2 for every molecule of calcium carbonate that is produced, according to the EDF.
Seaweed farming globally could remove up to 140 million metric tons of carbon dioxide annually by 2050. That amount of removed C02 is equivalent to cutting emissions from 42 million passenger vehicles or more than 300 million barrels of oil consumed, according to the greenhouse gas equivalencies calculator of Natural Resources Canada.
“Seaweed farming offers a scalable, nature-based solution for carbon removal while delivering co-benefits such as biodiversity enhancement, economic opportunities, and food security,” added Duarte, lead author of the Oceans 2050 study. “This research is a pivotal step towards integrating seaweed aquaculture into global climate strategies.”
The Oceans 2050 group believes the study findings highlight the need for robust frameworks to develop carbon credits for seaweed farming, ensuring that this “Blue Carbon” strategy is allowed to be integrated into carbon markets. Seaweed farming has the potential to become a foundation of the regenerative Blue Economy by prioritizing marine spatial planning and sustainability.
Expanded seaweed farming also could benefit economic balance considering that many participating farms are operated by women from coastal communities in developing countries, according to Oceans 2050.
The Global Seaweed Project has been funded by the World Wildlife Fund (WWF), the Bezos Earth Fund through WWF, the Grantham Foundation, and Climateworks Foundation, to enable research and impactful initiatives.
Blue carbon is a term for carbon captured by the world’s ocean and coastal ecosystems, according to the U.S. National Oceanic and Atmospheric Administration.
“The bigger picture of blue carbon is one of coastal habitat conservation,” reads the NOAA definition of blue carbon. “When these systems are damaged, an enormous amount of carbon is emitted back into the atmosphere, where it can then contribute to climate change. So protecting and restoring coastal habitats is a good way to reduce climate change.”
Many strains of algae also are the focus of long-term research for carbon capture and utilization (CCU) benefits. A report in Science of the Total Environment contended that algae-driven CCU was promising as a tool for achieving carbon-neutrality goals such as net zero.
For several decades, oil and gas producer Exxon Mobil worked on ways to cultivate algae and convert it into a feedstock for biofuel. In 2023, however, Exxon Mobil dropped out of the longtime research, while its former partner Viridos found other investors in United Airlines, Chevron and Breakthrough Energy Ventures.
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