Taking carbon farming out to sea

The untapped potential of seaweed

5 min readAug 12, 2020


An image of seaweed in the ocean.
Scientists are uncovering the important role that seaweed plays in the global carbon cycle. (Photo: Flickr).

by Maya Glicksman, agriculture and soil science intern and Olivia Hemond, blue carbon science intern

The fight against climate change is often waged on land, where we live, work, and breathe. But to fully take action, we need an approach that is truly global — and that means including our oceans. Just like land agriculture, ocean-based farming can become a climate mitigation tool. Its potential relies on one key crop: seaweed.

Seaweed accounts for half of all food farmed in the ocean and is used for a range of biomedical and industrial purposes. Many countries, most notably China and Indonesia, already harvest millions of tons of seaweed every year. While seaweed is a staple around the world, scientists are only beginning to evaluate its potential to remove carbon from the atmosphere and help combat climate change.

Seaweed’s carbon storage potential

Natural seaweed carbon sequestration processes can be harnessed by specially designed farms. (Image: Harvard University)

Recent research has discovered that seaweed plays a huge role in oceanic carbon sequestration. Wild, uncultivated seaweed is responsible for sequestering over a hundred million metric tons of carbon in the deep ocean every year. They live and grow, then die and decompose into bits and pieces that slowly make their way down to the ocean floor, taking their carbon with them. Once locked in the deep ocean, this carbon can be stored for hundreds or thousands of years.

Scientists are exploring if seaweed farming practices could mimic this natural sequestration process to draw down and store more carbon in the deep ocean. Preliminary models have estimated that no-harvest seaweed farms on just 3.8% of US West Coast waters could store 34.4 million metric tons of CO2 — an amount equal to all direct emissions from California’s agriculture industry. Kick-starting pilot projects could help us better demonstrate how much carbon this strategy could remove in practice. Since the US does little seaweed farming now, to reach this scale, policy is needed to support research, development, and deployment.




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