Seaweed Farms Are An Important Carbon Sequestration Strategy – CleanTechnica

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We know that plants sequester carbon dioxide. The Amazon rainforest (what’s left of it), mangrove swamps, and sea grasses all remove carbon dioxide from the air. But a recent study by the Oceans 2050 Global Seaweed Project found that seaweed farming can also be an important source of carbon sequestration. Launched in September 2020, the Global Seaweed Carbon Project aims to harness the power of seaweed farming to mitigate climate change and restore ocean health. The ultimate goal is to create the conditions needed to scale up seaweed farming, potentially removing gigatons of atmospheric carbon dioxide and regenerating our oceans. Oceans 2050 is not just another nonprofit; it is headed by Alexandra Cousteau, granddaughter of the renowned oceanographer Jacques Cousteau.

On its website, Oceans 2050 says, “Our research lays the foundation for integrating seaweed farming into carbon markets, unlocking new opportunities for sustainable aquaculture. By enabling the creation of verified carbon credits, it offers a vital tool to mitigate climate change while benefiting coastal communities. Seaweed farming not only removes atmospheric CO2 but also provides economic opportunities, food security, and resilience for some of the world’s most vulnerable populations, making it a cornerstone of the regenerative Blue Economy.”

This latest research into seaweed farming and carbon sequestration was headed by Oceans 2050 chief scientist  Carlos Duarte, a marine ecologist with a global reputation for conducting research on marine ecosystems from the polar regions to the tropical ocean and from near shore to deep sea ecosystems. His research addresses biodiversity in the oceans, the impacts of human activity on marine ecosystems, and the capacity of marine ecosystems to recover from these impacts. He is also interested in collaborating with scientists and engineers across a broad range of fields to solve problems in the marine ecosystem and society. “We have a narrow window of opportunity to deliver a healthy ocean to our grandchildren’s generation, and to create sustainable enterprises along the way. This study will help accelerate progress by creating evidence-based pathways to restore oceans and the climate through innovative, market-based sustainability solutions,” Duarte says.

The Oceans 2050 Seaweed Study

This study was published January 17, 2025 in the journal Nature Climate Change. Here is the abstract:

Seaweed farming has emerged as a potential Blue Carbon strategy, yet empirical estimates of carbon burial from such farms remain lacking in the literature. Here, we quantify carbon burial in 20 seaweed farms distributed globally, ranging from 2 to 300 years in operation and from 1 to 15,000 ha in size. The thickness of sediment layers and stocks of organic carbon accumulated below the farms increased with farm age, reaching 140 tC ha−1 for the oldest farm. Organic carbon burial rates averaged 1.87 ± 0.73 tCO2e ha−1 yr−1 in farm sediments, twice that in reference sediments. The excess CO2e burial attributable to the seaweed farms averaged 1.06 ± 0.74 CO2e ha−1 yr−1, confirming that seaweed farming in depositional environments buries carbon in the underlying sediments at rates towards the low range of that of Blue Carbon habitats, but increasing with farm age.

Putting aside the scientific jargon, two notable aspects of the research are that one of the seaweed farms covers nearly 58 square miles and that older seaweed farms do a better job of carbon sequestration. According to an email to CleanTechnica, the study not only underscores the ability of seaweed farming to combat climate change, but also its capacity to drive food security, gender equity, and local economic resilience in coastal communities. As Cousteau pointed out, “Seaweed farming offers a scalable, nature based solution for carbon removal while delivering co-benefits such as biodiversity enhancement, economic opportunities, and food security.” The research was supported by the Bezos Earth Fund and WWF, along with the Grantham Foundation, and Climateworks Foundation, and is enabling groundbreaking research and impactful initiatives.

The study, entitled “Carbon burial in sediments below seaweed farms matches that of Blue Carbon habitats,” marks the first comprehensive, empirical assessment of carbon burial rates beneath seaweed farms globally. It was conducted across 20 seaweed farms on five continents, and confirms that seaweed farming can sequester carbon in the sediments beneath them at rates comparable to vegetated coastal ecosystems like mangroves, salt marshes, and sea grasses. Key findings of the study include:

• Seaweed farms bury carbon at rates similar to mangroves and seagrasses, two ecosystems already known for their climate benefits.
• Older and larger seaweed farms store more carbon, showing that sustainable farming can have lasting impacts.
• If expanded worldwide, seaweed farming could remove up to 140 million tons of CO2 from the atmosphere every year by 2050.

“This research provides compelling evidence of the critical role that seaweed farming can play in addressing the climate crisis,” said Cousteau. “By quantifying its carbon sequestration potential, we hope to unlock new avenues for investment in sustainable aquaculture as a climate solution.” The findings also underscore the need for robust frameworks to develop carbon credits for seaweed farming, ensuring that this promising Blue Carbon strategy can be integrated into carbon markets. By prioritizing marine spatial planning and sustainability, seaweed farming has the potential to become a cornerstone of the regenerative Blue Economy.

The Global Seaweed Project

The research is part of Oceans 2050’s Global Seaweed Project, launched in September 2020, and marks a pivotal milestone in the advancement of the seaweed industry, providing a robust scientific foundation for the creation of a verified carbon credit methodology. By quantifying the carbon sequestration potential of seaweed farms, the Global Seaweed Project demonstrates the feasibility of creating a new blue carbon market that can support both climate mitigation and the development of a sustainable Blue Economy. Additionally, the project highlights the significant social impact of seaweed farming, with over 99% of participating farmers, most of whom are women, coming from coastal communities in developing countries. In 2021, the Global Seaweed Project was awarded the prestigious Keeling Curve Award that recognizes outstanding initiatives to reduce greenhouse gas emissions.

The study incorporated scientific research conducted at 20 seaweed farms in countries including Japan, Indonesia, Norway, and Chile. The researchers partnered with leading scientific laboratories in Spain, Australia, and Monaco to analyze data and develop robust methodologies. “We are proud of our global network of seaweed farms, involving about 27,000 farmers; the first ever of this nature, which has allowed us to assess carbon sequestration benefits but has also provided evidence of the huge positive social impact seaweed farming brings to coastal communities, empowering the role of women who make up the majority of seaweed farmers,” said Alexandra Cousteau.