Around the globe, approximately 12 million tonnes of seaweed are grown and harvested annually. The cultivation of seaweed is a $5-5.6 billion industry, which continues to expand. China alone grows about three-quarters of the global total. About $5 billion of the current market value is from the sale of human consumption. Apart from the health benefits that seaweed gives humans, it has also been found to de-acidify seawater and enhance the growth of shellfish. Studies have found that seaweed farming has the potential to help mitigate climate change because of its capacity to absorb carbon dioxide from the atmosphere.
The Rise of Seaweed Farms
In China’s Yellow Sea, large scale seaweed farming has long been practiced to grow seaweed and enhance shellfish cultivation. Some farms in China grow over 500 square kilometers of seaweed. In the United States, kelp cultivation is becoming integrated in sustainable marine farms. Although seaweed farming is in its early stages of development, the methodology is seen as a feasible way to buffer the ocean’s increasing acidity levels and to boost seafood production.
One example of a successful seaweed farm is Bren Smith’s 3D Ocean Farming located in Long Island South, near New Haven, Connecticut. His farm consists of floating ropes, where he grows kelp and mussels. Hanging from the ropes are baskets filled with oysters and scallops. Smith’s enterprise produces about a million bivalves and 40 tonnes of kelp per hectare annually. Although his farm took some hard hits from hurricanes Irene and Sandy, Smith’s persistence has turned into a profitable enterprise.
Like terrestrial plants, kelp can absorb large amounts of carbon dioxide from the atmosphere, which also helps to de-acidify the ocean. As the water becomes less acidic, shellfish are able to thrive. Seaweeds can grow at a faster rate than land plants, sometimes 30 times faster! Farmed seaweed is also used for various industrial purposes, such as feedstock in agriculture. Because of the productivity potential of seaweed farms, Smith and his team established a non-profit called Green Wave to help others establish their sustainable farming models.
Potential to Offset Climate Change
A study published in 2012 by the University of the South Pacific looked at the potential of seaweed farms to combat climate change. Dr. Antoine De Ramon N’Yeurt and his team found “that if 9% of the ocean were to be covered in seaweed farms, the farmed seaweed could produce 12 gigatonnes per year of biodigested methane which could be burned as a substitute for natural gas.” 9% seems like a small percentage, but 9% of the ocean equates to about four and a half times the area of Australia. Growing seaweed at this scale could capture up to 19 gigatonnes of carbon dioxide.
Researchers of the study also said that seaweed farming “could produce sufficient biomethane to replace all of today’s needs in fossil-fuel energy, while removing 53 billion tonnes of CO₂ per year from the atmosphere… This amount of biomass could also increase sustainable fish production to potentially provide 200 kilograms per year, per person, for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity.”
Although large scale seaweed farming has yet to gain momentum, researchers believe that small scale kelp farming still has the potential to absorb significant amounts of carbon dioxide from the atmosphere. Even though seaweed farming has the potential to help combat climate change, more people are driven by the potential it has to sustainably produce high-quality protein. But regardless of which of these benefits is held to a higher esteem, both have driven research initiatives and commercial development of sustainable agriculture.