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Can Seaweed Save The World?

It’s no secret that the ocean can do amazing things, from providing a home to nearly 230,000 known species to creating gnarly waves for amped-up surfers. The ocean might also be a key to battling climate change by reducing the earth’s excess carbon. One company working to harness the ocean’s power to help offset climate change is Running Tide of Portland, Maine.

Running Tide, a startup that raises shellfish as its primary business, is also working on a project to raise kelp in the open sea and then sink it to the ocean floor to sequester the carbon inside. Kelp are a type of seaweed composed of large brown algae that live in cool, shallow waters near the shoreline. Like trees and other land plants, seaweed use photosynthesis to turn carbon dioxide (CO2) into a biomass that can quickly suck up carbon. When the CO2 is locked up in seaweed biomass, it can either be harvested for food or other uses or sink to the seafloor where the carbon is returned to the earth.

The advantage of using seaweed to store carbon is that it’s less vulnerable to devastation than land plants. Trees can burn down at a rapid rate — as evidenced by the 2 million acres of California forestland that have been lost to fires this year alone. But seaweed that finds the ocean floor can remain there for centuries.

“Once it goes down below 1,000 meters, it’s not coming back up because the pressures are so great,” Running Tide founder Marty Odlin recently told Fast Company. “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.”

The impact on global warming could be significant. A 2019 study found that growing and sinking macroalgae in a tiny fraction of the federal waters off of California’s coast could fully offset emissions from the state’s huge agriculture industry.

As noted in National Geographic, scientists call these kelp forests the “sequoias of the sea” for their ability to store large amounts of carbon dioxide. In ideal conditions, kelp can grow up to 18 inches per day, providing food and shelter for thousands of organisms. Around 800 marine species, including sea otters, depend on kelp forests to survive.

The challenge now is figuring out how to make carbon sequestration of seaweed a viable economic option.

“For a seaweed carbon sequestration market to exist there must be someone willing to pay to store carbon in seaweed,” marine biologist Heather Kramp wrote in an article for the California Sea Grant website. “Presently, there’s no carbon credit exchange market for seaweed. Government policies need to support industry development. Policies that encourage aquaculture, a streamlined permitting process, and no overly strict regulations can help new farmers and investors enter the industry. Unfortunately, many agencies have no framework for seaweed aquaculture and are tripping over out-of-date, restrictive policies.”

Strides are being made, however. For example, four years ago the Port of San Diego launched its Blue Economy Incubator to support emerging aquaculture and so-called “blue technology” businesses.

“Having a state agency support development of the seaweed aquaculture industry is a much-needed asset,” Kramp noted. “Keep your eyes on the coast, because seaweed aquaculture may soon be tackling climate change.”


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