A new model for kelp farming as a climate solution in Maine

Cole Roxbury, a marine science student at the University of Maine, holds a rope of kelp at the Darling Marine Center. Photo by Adam St. Gelais of the University of Maine.

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Researchers at the University of Maine have modeled what they say is the cheapest and most efficient way to store carbon in kelp grown deep below the surface of the Gulf of Maine.

The new study, published recently in the journal Frontiers in Marine Science, offers a potential route to what some see as a crucial tool for pulling the world from the brink of climate catastrophe – but the nascent field still has a long way to go.

Kelp farming is a hot business in Maine — at the grocery store, you’ve probably seen products like fruit-flavored frozen kelp cubes from companies like Biddeford-based Atlantic Sea Farms, which received an article praise this summer from the Washington Post. climate and food counter.

The value of this “macroalgae” as a climate solution lies in the speed of its growth and the way it degrades. Kelp quickly extracts carbon from the air through photosynthesis when it grows on rocky coasts like Maine’s – ecosystems that can store up to 20 times more carbon per acre than a terrestrial forest. This kelp gradually breaks down and drifts in pieces to the ocean and to the depths, where it tends to remain intact and unable to re-enter the atmosphere.

It was this process that put kelp farming on the table as a potential carbon storage technique. In their new study, the UMaine researchers wanted to see what it would look like to do this at scale, with the most carbon stored at the lowest cost.

The model they devised involves farming the kelp far offshore and then transporting it even farther to deep-water “sink sites.” Carbon-rich kelp could be deposited in sediments more than 1,000 meters deep, or sent “below the permanent thermocline” – the threshold where ocean water changes from warmer and well-mixed near the surface to cold and calm at depth – “in areas of the ocean where carbon is prevented from returning to the atmosphere,” says UMaine.

This approach would reduce the cost of storing carbon in the kelp from $17,048 per ton of greenhouse gases to $1,257, according to the study. But the university’s press release notes that the industry’s goal for any carbon storage technology to be “economically viable” is closer to $100 a ton.

Experts agree that the world is on track to need as many of these viable solutions as possible. As companies and governments continue to burn and use more fossil fuels, moving towards the goals of the Paris climate agreements, it will not be enough to emit less – we will have to get rid of some of the emissions that we have already caused, using a range of capture and storage methods.

These approaches range from nature (planting trees, restoring wetlands and grasslands, improving soil health on farms) to heavy industry (sucking up carbon with giant fans and injecting it into deep deposits of rocks that can chemically bond to it). ) in between (kelp farming and other biomass-based industries).

For kelp, as in most of these cases, many questions remain about environmental trade-offs.

“We have no experience of disturbing the ocean floor with this amount of carbon,” Steven Davis, an associate professor at the University of California, told MIT Technology Review last year. “I don’t think anyone has a clear idea of ​​what it will mean to actively intervene in the system on this scale.”

And there are practical considerations. Maine’s coastal communities are notoriously skeptical of many forms of industrial aquaculture – see the ongoing debates over fish farming – and other ocean users, such as lobster fishermen, have balked at the idea. idea of ​​offshore wind turbines.

What answer might we expect, then, from farming kelp offshore and disposing of it on the high seas?

To read the full edition of this newsletter, see Climate Monitor: Carbon Storage in Kelp, plus PFAS and the Penobscots.

Annie Ropeik has been handed the keys to the Climate Monitor newsletter while its regular author, Monitor environmental reporter Kate Cough, is on furlough until November. Contact Annie with story ideas at: [email protected]