Seaweed farmers David Leith, left, and Stewart Hunt haul in a line of kelp for harvesting off the coast of Cumberland. Maine seaweed farmers are taking aim at the $6 billion global industry, harvesting 1 million pounds in 2022. Robert F. Bukaty/Associated Press

Three kelp farms operating off Long Island harvested more than 200,000 pounds of seaweed in 2022, which is about one-quarter of nearly 1 million pounds produced last year by some 40 growers along the Maine coast.

For Nathan Johnson, it’s a point of pride that Long Island produced more kelp than any other seaweed-farming community in the United States. His family has lived on the island and fished the waters of Casco Bay for centuries, and he sees kelp farming as a way to keep them there.

He’s also happy to promote his product as being harvested from the “pristine” waters of the Gulf of Maine, under strict regulations overseen by the state Department of Marine Resources.

It sets Maine’s farm-raised kelp apart from seaweed grown in Asia, which accounts for 97% of cultivated seaweed worldwide, according to the Food and Agriculture Organization of the United Nations. The farms overseas are massive and largely unregulated, with product that is untraceable and possibly polluted with heavy metals and other harmful materials, he said.

“Having a clean, high-quality product, Maine has an opportunity to capitalize on the comparison to other areas with lower water quality,” Johnson said. “It’s part of the Maine brand that you can build a business around.”

Johnson was among 300 attendees at “Seagriculture,” the second annual International Seaweed Conference USA, held this week at the Westin Portland Harborview Hotel. The two-day event featured presentations by global leaders in seaweed innovation exploring its production and various uses, including food, bioplastics, medicine and sustainable economic development.


International seaweed production is now a $6 billion industry, with output increasing from 34,700 tons in 1950 to more than 34.7 million tons today, according to the U.S. Department of Agriculture. Although Europe and Asia have outpaced the United States, seaweed farming is the fastest-growing sector of American aquaculture. Dozens of farms have taken off recently in the Pacific Northwest, Alaska and New England.

With a 50-year history of harvesting wild seaweed, Maine has quickly become the largest U.S. producer of farmed kelp, harvesting just under 1 million pounds, or 453 wet tons, in 2022, up from just under 53,000 pounds, or 24 tons, in 2018, according to various sources.

“Maine’s seaweed industry is experiencing tremendous growth, with farmers, producers, and researchers making contributions to this important economic sector,” said Heather Johnson, head of the Maine Department of Economic and Community Development, a conference sponsor.

The Maine Technology Institute, another sponsor, is investing in the state’s “seaweed economy,” offering grants, loans and equity investments to companies that are innovators in the industry, said Brian Whitney, institute president.

“Maine is already a leader in kelp farming and well-positioned to be at the forefront of advanced processing of seaweed,” Whitney said. “(That) will allow the industry to scale up and bring high value jobs to Maine.”

Briana Warner, chief executive officer of Atlantic Sea Farms, which partners with about 30 Maine fishermen, at Pine Point Beach in Scarborough. The company has drawn significant investment recently and has seen revenues increase 70% over the past year. Ben McCanna/Staff Photographer

Leading that growth is Atlantic Sea Farms in Biddeford. The company provides free seed to 30 kelp farmers – mostly lobstermen working their lines off-season – and buys everything they harvest, CEO Briana Warner said in her keynote presentation Thursday.


Atlantic transforms the kelp into frozen veggie burgers, Korean-inspired fermented seaweed salads and other food products, which are now sold in 2,600 stores, including Hannaford, Whole Foods and Albertsons. As a result, Atlantic is now responsible for producing about 85% of line-grown seaweed in Maine, Warner said.

To fund the expansion, Atlantic has raised $9.5 million from investors in the last five years and expects to become profitable within two to three, Warner said. Company revenues increased 70% in the last 12 months, she said.

But while the growth potential of Maine’s seaweed industry has drawn a lot of attention lately, it also has raised concern that expanded aquaculture could damage the marine environment.

“Maine has a strong, well-considered regulatory system that’s set up to keep out bad actors,” Warner said. But it can take up to three years to get state approval for a 4-acre kelp aquaculture site, she said. An effort is underway to streamline the review process without diminishing the regulations, she said.

Concern about the industry’s rapid growth cropped up repeatedly at the conference as speakers from Maine and other states shared the stage with experts from the Netherlands, Norway, Kenya and South Korea. At the same time, a conference banner posed the question, “Why Maine? Pristine Waters. Innovative Spirit. Sustainability Culture.”

Mitchell Lench, founder and CEO of Ocean’s Balance, discussed his recent purchase of a massive kelp drying machine that he said may allow Maine seaweed companies to triple production. Several speakers discussed using technology to develop “smart seaweed farming.”

“Growth is not necessarily the answer if your interest is sustainability,” said Shep Erhart, co-founder and president of Maine Coast Sea Vegetables in Hancock. He advised against farming nonnative species, overharvesting seed beds, negative impacts of large-scale farms and the use of non-biodegradable rope.

For Johnson, the Long Island kelp farmer, preserving Maine’s marine resources is the same as preserving his family’s heritage. His father and oldest son are lobstermen.

“The biggest challenge facing kelp farmers is ensuring the responsible growth of the industry,” he said. “We need to make sure we have all stakeholders engaged in the process.”

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