Seaweed to Remove 550 Million Tons of Carbon Dioxide From the Atmosphere Every Year

Researchers from the Max Planck Institute for Marine Microbiology in Bremen, Germany have found that brown algae take up large amounts of carbon dioxide from the air and release parts of the carbon contained therein back into the environment in mucous form.

This mucus, called fucoidan, is hard to break down for other ocean inhabitants, thus the carbon is removed from the atmosphere for a long time, the researchers estimate that brown algae could thus remove up to 550 million tons of carbon dioxide from the air every year – almost the amount of Germany's entire annual greenhouse gas emissions.

Brown algae are true wonder plants when it comes to absorbing carbon dioxide from the air and even outcompete forests in this, and thus play a decisive role for the atmosphere and climate. Brown algae can remove large amounts of carbon dioxide from the global cycle in the long term and thus can counteract global warming.

Algae take up carbon dioxide from the atmosphere and use the carbon to grow. They release up to a third of the carbon they absorb back into the seawater, for example in the form of sugary excretions. Depending on the structure of these excretions, they are either quickly used by other organisms or sink towards the seafloor.

“The excretions of brown algae are very complex and therefore incredibly complicated to measure,” says first author Hagen Buck-Wiese from the Max Planck Institute for Marine Microbiology in Bremen. “However, we have managed to develop a method to analyse them in detail.” With this method, the researchers scrutinised a large number of different substances. The so-called fucoidan turned out to be particularly exciting. “Fucoidan made up about half of the excretions of the brown algae species we studied, the so-called bladderwrack,” says Buck-Wiese. Fucoidan is a recalcitrant molecule.

“The fucoidan is so complex that it is very hard for other organisms to use it. No one seems to like it.” As a result, the carbon from the fucoidan does not return to the atmosphere quickly. “This makes the brown algae particularly good helpers in removing carbon dioxide from the atmosphere in the long term – for hundreds to thousands of years.”

The recognition of seaweed in reducing CO2 emissions is already being recognised in Asia. ESGnewsasia recently reported that after quantifying the amount of CO2 absorbed by seaweed growing on the seawall around the Kansai International Airport, Kansai Airports had obtained J Blue Credit certification, a credit certified, issued and managed by Japan Blue Economy Association.

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