Seaweed as a climate solution: Sink or swim?
Imagine an epic drought is coming. You only have a few hours to store water for your family.
You have a swimming pool connected to a garden hose. You also have a bathtub connected to a fire hose. Which do you choose?
Those are the analogies I use to compare two natural carbon storage reservoirs available to solve the climate emergency. A tree forest on land is your swimming pool, and a seaweed farm in the ocean is your bathtub.
Both can absorb and store carbon (carbon dioxide is the water in this analogy), but they are very different when it comes to 1) the rate at which they can store carbon and 2) how much carbon they can hold.
Of course the answer to the first question is “both.” Photosynthesis is our most scalable, cost effective, and self-sustaining solution to moving carbon out of the atmosphere, and we should employ both land and sea to do it.
A tree forest can lock up carbon and direct it to long-term storage in the wood of its trunks and roots. Below ground, thick layers of soil can hold even more tons of carbon. It takes decades for a forest to pack all that carbon into its three dimensional lockbox.
By contrast, a seaweed forest doesn’t have wood. It doesn’t have soil. But it grows really, really fast — a photosynthetic overachiever, it converts carbon dioxide into plant matter at a phenomenal rate. Hence the fire hose analogy.
The high rate of photosynthesis combined with the smaller size of the reservoir means a seaweed forest reaches its storage capacity quickly — in only a matter of months. To maintain its ability to keep hoovering up carbon at fantastic rates, the best thing we can do with seaweed is to continuously harvest it and put that carbon to work.
We have two options. The first, which is increasingly gaining attention as a massively scalable climate strategy, is to sequester it in a permanent lockbox, like burial in deep ocean trenches. The second, which my company is working on, is to employ seaweed as a replacement for products with big climate footprints. Specifically, a better alternative to animal protein.
We can do this without touching natural seaweed forests, and by building seaweed farms. The extent of naturally occurring seaweed forests is limited by a need to hold on to something solid, while also getting sunlight. That’s why we find them in shallow waters with rocky bottoms. We can expand seaweed forests by building artificial seaweed farms in deeper water. On top of providing climate solutions, seaweed farms will provide expanded habitat for ocean ecosystems, since they act as nurseries for important species in the ocean food web.
The bottom line is the best way to use seaweed to mitigate climate change is summed up as: build it, sink it, or (if I have a say): eat it.
