Off the coast of Portland, Maine, an aquaculture startup that raises shellfish is also working on a more radical project: raising kelp in the open ocean, then sinking it to the seafloor to sequester the carbon inside.
The company, called Running Tide, argues that the approach could be essentially a permanent way to deal with the excess carbon in the atmosphere. Like trees, seaweed forests suck in carbon from the air as they grow. But while carbon in forests on land can sometimes be lost—as in California, where more than 2 million acres of trees have burned so far this year—kelp that sinks to the bottom of the ocean can stay there for centuries.
“Once it goes down below 1,000 meters, it’s not coming back up, because the pressures are so great,” says Marty Odlin, the founder of Running Tide. “So you can get at least 1,000 years of sequestration. More likely, it will turn into oil or sediment and be sequestered on the geologic timescale—millions of years.”