How Kelp and Seaweed Farming Can Help Capture Carbon Dioxide and Support Ocean Health

Our oceans have an important role to play in helping restore our climate.  Scientists agree that in order to curb the effects of heat-trapping gases, the world needs to innovate and find new ways to speed up carbon dioxide removal from the atmosphere. Since oceans cover two-thirds of the Earth’s surface, and already accumulate and store a large amount of carbon dioxide, they have an important role to play. Each year, the ocean naturally exchanges with the atmosphere almost a hundred billion tonnes of carbon as carbon dioxide. 

Our oceans absorb carbon dioxide through diffusion. Diffusion occurs when molecules in an area of high concentration move to areas with a lower concentration. Since our atmosphere contains more carbon dioxide than the ocean, carbon dioxide diffuses from the atmosphere into the ocean. As long as the concentration of carbon dioxide in the atmosphere is higher than it is in the oceans, the ocean can capture carbon. 

When carbon dioxide diffuse from the atmosphere into the ocean, it  dissolves. And when it dissolves, it combines with the water to form carbonic acid. As the amount of carbon dioxide in our atmosphere has increased, so has the amount of carbon dioxide taken up by the ocean. Greater amounts of carbon dioxide dissolving into the water is causing the ocean to become more acidic.  

An increasingly acidic ocean in turn is making it harder for ocean species, such as oysters and corals, to form their hard shells and skeletons. While some species will be harmed by ocean acidification, algae and seagrasses may benefit from higher carbon dioxide conditions in the ocean, as they require carbon dioxide for photosynthesis just like plants on land.  In the 200 years since the Industrial Revolution began, ocean acidity has increased about 30 percent. 

Recently, at a California oyster hatchery, farming native seaweed was shown to improve water quality. ​​The study showed that native kelp farms helped reduce harvesting pressure on wild seaweeds, as well as absorbing carbon and nitrogen pollution. 

Travel journalist, photographer and Tomorrow's Air supporter Jonny Bierman recently shared with us some of the places he has found most inspiring and motivating for his own climate action, including a kelp farm in San Luis Obispo, California. He shared this in a recent article: “Outside the city, farms of all kinds toil away at the rich soils and waters of San Luis Obispo to bring fresh produce to the markets, and to make some of the best wine in the nation. To invite visitors to experience both, winemakers rooted in sustainable and organic winemaking, marked by SIP (Sustainability in Practice) Certification, have joined forces with regenerative farming businesses to create a self-guided tour on the SLO County Farm Trail

As a result you can try your hands at harvesting kelp, or simply purchase kelp products, with Kelpful–a worker-owned, women-run cooperative with the goal of bringing regenerative sea vegetables and shellfish to the Central Coast community.”  Learn more about the this remarkable spot in his Conde Nast Traveler article

In another project in California, this one in Tomales Bay, north of San Francisco, the Salt Point Seaweed Company is working with a similar goal of cultivating seaweed to support ocean health and capture carbon dioxide. In a pilot project funded by NOAA SeaGrant the company’s small team grew native red algae Gracilariopsis andersonii in Tomales Bay. Analsysis showed the seaweed successfully removed carbon and nitrogen from the surrounding water.Their  long-term vision is to create food products sourced solely from farmed seaweed.

Before the industrial age, the ocean vented carbon dioxide to the atmosphere in balance with the carbon the ocean received during rock weathering. Since carbon concentrations in the atmosphere have increased, the ocean now takes more carbon from the atmosphere than it releases. 

Exploring ways to increase the amount of carbon dioxide stored in the ocean without increasing ocean acidification is an important and ongoing field of study. Learn more about what the National Academies for Science, Engineering and Medicine are recommending for research and development in this area of carbon removal.

Photo courtesy Jonny Bierman

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