Seaweed farms show potential for carbon storage that gets better with age

Location of sampled seaweed farms, time elapsed (years) since the start of farming and the size of the harvested area (HA). Credit: Natural Climate Change (2025). doi:10.1038/s41558-024-02238-1
A large team of researchers from diverse backgrounds has found evidence that carbon storage beneath seaweed can accumulate as much carbon as some blue carbon habitats. In their study, published in Nature Climate Change, the group analyzed data from multiple seaweed farms around the world.
As climate change advances, scientists are seeking new ways to remove carbon from the atmosphere. Many in the field point out that natural or at least semi-natural approaches are likely to become more acceptable due to lower costs. For example, planting trees is cheaper than building millions of carbon-seating machines.
In this new study, researchers looked at the possibility of using seaweed farms to extract carbon from seawater.
The work involved analyzing data collected by operators of 20 seaweed farms around the world. The researchers note that the farms they studied ranged in age from 2 to 300 years old and ranged in size from 1 to 15,000 hectares.
Data, including measurements of carbon sequestered under seaweed, showed that newer farms sequestered more carbon than older farms. Researchers found that some of the oldest farms sequestered 140 meters of carbon per hectare. They also found that the average amount of carbon buried beneath all the farms they studied was about twice as much as the layer of sediment near the farms.
Researchers suggest that seaweed farming, especially where sediment naturally accumulates, can sequester carbon at rates close to those of some coastal environments, such as mangrove forests.
Details: Carlos M. Duarte et al. Carbon burial in sediments beneath seaweed farms matches that of blue carbon habitats, natural climate change (2025). doi:10.1038/s41558-024-02238-1
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