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Carbon Sequestration: Seaweed

A quick fact check.

I hope all are well during these difficult times.

I am often surprised by some of the claims about seaweed and carbon sequestration. So, I figured it was worth a quick fact check.

Kelp forests can sequester up to 20 times more carbon than terrestrial forests. A truly amazing figure. Like land forests, this carbon sequestration depends on these forests being healthy and undisturbed. Harvesting seaweed like harvesting forests releases its carbon into the atmosphere, i.e., it is no longer sequestered.

Seaweed can help sequester carbon if we eliminate or reduce the wild harvest of seaweeds, and increase our efforts to protect kelp forests and to increase our kelp reforestation efforts.

Farmed seaweed for food, like farmed vegetables, does not significantly sequester carbon. Once land or terrestrial plants are used as a food it returns to the atmosphere through the carbon cycle. The benefit of seaweed farming to the environment is potentially its significant capacity to reduce ocean acidification. This effect tends to be localized, but can still be important.

A truly impressive carbon sink is in our soils. Regenerative farming practices such as "no-till" and the reduced use of synthetic fertilizers can potentially sequester up to 30% of our current carbon gas emission increases. Seaweed fertilizers from farmed seaweeds can play a significant role in the sequestration of carbon in our soils by displacing synthetic fertilizers in the marketplace.

In summary, we should:

  • Cease or dramatically reduce the harvesting of wild seaweeds;
  • Invest in the reforestation of our kelp forests;
  • Eat farmed seaweeds to help reduce ocean acidification; and
  • Produce farmed seaweed based fertilizers to support soil based carbon sequestration.

Note, the MSE "EFOS" (Eat Farmed Organic Seaweed) initiative is part of our effort to encourage the utilization of farmed versus wild harvested seaweeds for food.

 

The MSE is also supporting research to create high value seaweed based fertilizers from farmed seaweed.

In summary, we should:

  • Cease or dramatically reduce the harvesting of wild seaweeds;
  • Invest in the reforestation of our kelp forests;
  • Eat farmed seaweeds to help reduce ocean acidification; and
  • Produce farmed seaweed based fertilizers to support soil based carbon sequestration.

Note, the MSE "EFOS" (Eat Farmed Organic Seaweed) initiative is part of our effort to encourage the utilization of farmed versus wild harvested seaweeds for food.

ADDENDUM: In a recent conversation I was asked how seaweed can sequester carbon? Thus this post!

Expanding on my comments above, it is worth discussing how seaweed sequesters carbon.

First, carbon is sequestered in the living tissue of the seaweed similar to a land forest.

Second, seaweed breaks off in storms and through other processes. This seaweed either washes ashore or settles to the ocean floor. The seaweed that settles to the ocean floor becomes incorporated into sea floor sediments. Depending on the nature of this sediment the seaweed carbon is sequestered for either a short period or possibly permanently if the depth is great enough.

Farming seaweed releases up to 10% or more of the biomass cultivated to the sea. This seaweed is subject to sequestration similarly to wild seaweeds. So a small percentage of farmed seaweed will contribute some carbon sequestration. This is good, especially as it helps offset the fossil fuels utilized to grow and process farmed seaweed.

The MSE is seeking funding to do research on the real carbon footprint of seaweed farming, as well as explore the potential of growing seaweed specifically to be sunk to the ocean floor to sequester carbon. Currently the cost of farming exceeds the value of the carbon that can be sequestered by intentional release, however the MSE's work on growing year round seaweed crops may change this equation.

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