About 5 miles off the coast of Santa Barbara, California, a vast swath of giant kelp—Macrocystis pyriferia, which can grow nearly 3 feet per day—sways just below the surface of one of the world’s first open-ocean seaweed farms.

Still in its research phase, the 86-acre project is operated by Ocean Rainforest, a company that aims to fight climate change by growing seaweed at scale: 1 million tons a year by 2030. Although an 86-acre terrestrial farm would be considered boutique, the Ocean Rainforest plot, floating in sight of the Channel Islands, represents a significant leap in size from the average U.S. seaweed farm of 1 to 4 acres—and a new frontier for ocean farming.

Supported by $6.2 million in Series A funding, for a total of $22 million from U.S. and European governments, grants, and venture capital, Ocean Rainforest also operates seaweed farms in the Faroe Islands and Iceland that supply the animal-feed, fertilizer, and cosmetic industries. The company’s goal of substantially decarbonizing these industries—with seaweed, instead of petroleum feedstocks, as raw material—depends on the success of this farm. Growing seaweed in the open ocean, with room to exponentially expand, means the Ocean Rainforest team is tackling how to anchor crops in hundreds of feet of water, withstand intense weather, and monitor a farm that lies many miles from shore.

As Ocean Rainforest continues its research, the wider U.S. seaweed industry, still in its infancy, faces significant challenges. Several years of steady investment and scientific breakthroughs have helped it advance, but since 2023, funding has dropped precipitously, and so have retail prices for seaweed-based foods. In the meantime, a lack of government guidance by means of regulation and legislation makes it difficult for farms to gain traction. Seaweed is an extraordinary crop, offering multiple benefits to planetary and human health along with an array of business applications. But it’s fair to say that right now, the industry is having growing pains.

The Investment Slowdown

In 2023, according to Phyconomy, a database that tracks the seaweed economy, seaweed funding in the U.S. abruptly began to sink, dwindling from a peak of about $100 million in 2022 to just $8 million for 2024 so far.

“We are in what I call the ‘valley of disappointment,’” says Steven Hermans, who founded Phyconomy. American investors have become more sophisticated about startup investments, including in seaweed, he says. A few years ago, he adds, “They didn’t know anything, and they were like, ‘OK, we’ll toss a couple of million into this.’ Then, Everyone kept their money in their pockets during high inflation … [and] people realized … it will take a long time to build a market for American-grown kelp. Now they’re asking better questions, and that will ultimately lead to better investments.”

But for some companies, that won’t matter. Since Civil Eats began this reporting project nearly a year ago, two of the largest and most well-known American kelp businesses have gone under: Running Tide, a carbon capture company, and AKUA, maker of kelp burgers.

Founded in 2017 by Marty Odlin, the Maine-based Running Tide was one of the most well-funded kelp companies in the U.S. before it shut down abruptly in June 2024. As its website stated, Running Tide aimed to build “humanity’s operating system for the ocean,” drawing down carbon via seaweed-inoculated wood chips. Seaweed naturally absorbs carbon as it grows, but unless it is harvested, it decomposes and releases carbon back. The chips, on the other hand, would sink to the deep ocean to decay, storing the carbon there for thousands of years, according to Odlin. Running Tide’s revenue goal was to sell carbon removal credits to companies interested in decreasing their carbon footprint.

Running Tide garnered $54 million in Series B investments, including from Lowercarbon Capital, in 2022. In June of that year, an article in the MIT Technology Review questioned Running Tide’s farming and business practices. Meanwhile, the company prepared to relocate to Iceland, having persuaded the Icelandic government to approve its wood-chip sinking.

In fall 2023, Running Tide sank 19,000 tons of wood chips into the ocean, selling the world’s first marine Carbon Dioxide Removal (mCDR) credits to Microsoft and Shopify as part of a voluntary carbon market not regulated by government. In less than a year, the company shut down as criticism about its practices continued to swirl; Odlin cited a lack of American government support for the voluntary carbon market as the reason for the closure.

Although $54 million represented a fraction of the $380 million overall investment in the seaweed industry, some think the carbon-sink goal was too narrow, and overlooked all that seaweed could offer. “The long-term carbon sink potential attracted a swarm of speculators that took the industry in the wrong direction,” says Bren Smith, founder of GreenWave, a forerunner in the ocean farming movement. GreenWave received roughly $6 million in 2021.

Smith believes that the dip in carbon-fueled funding will encourage the industry to embrace seaweed’s many uses—as a good food for humans and animals, as a game-changing alternative to chemical- and carbon-intensive industries like fertilizers or plastics, and for its proven ecosystem benefits. Also, seaweed doesn’t need arable terrestrial land, likely to diminish as wildfires and extreme weather events like drought increase. “I don’t know if it’s 100 years or five years, but we’re gonna be growing huge amounts of food underwater,” he predicts.

Lack of Federal Funding

The slump in private investment isn’t the only financial challenge for seaweed. Scant federal funding adds to the struggle. In Europe, many ocean startups receive government support, according to Ronald Tardiff, Ocean Innovation Lead at the World Economic Forum, whereas in the U.S., most government funding goes to research institutions rather than for-profit companies. (The Department of Energy, an important source of research funding dating back decades, contributed some $20 million to seaweed research in the 1970s through its MARINER program, and continues to support science; see “Seaweed Investments by Category” below.)

“The E.U. has spent … . hundreds of millions of euros on R & D related to seaweed, in a way that the U.S. has not. And many startups have benefited from those E.U. projects,” says Tardiff, pointing out that Ocean Rainforest, a for-profit entity, has received extensive E.U. funding. In China and Korea, where seaweed farming first developed into a larger industry, governments provide kelp seed to farmers for free or at a subsidized cost. The lack of state support in the U.S., says Tardiff, also means the American seaweed market is more tied to market fluctuations than its Asian and European competitors.

The paucity of both private and government funding makes it harder for seaweed companies to handle the high cost of farming and processing. “The ocean is uniquely expensive to operate on,” says Tardiff, who also serves as the Lighthouse Lead of 1000 Ocean Startups, a global coalition of incubators, accelerators, competitions, matching platforms, and VCs that have pledged to back at least 1,000 “transformative” startups by 2030.

Basic seaweed farming equipment, like a boat, costs anywhere from $30,000 to $500,000; a single seaweed-line anchor—and a farm needs multiple—can cost $1,000. Also, because kelp is unusually perishable, it requires million-dollar investments in infrastructure equipment, like specialized dehydrators and freezers, to render it shelf-stable. Much of it is custom-built for this new food business.

Retail Slump Meets Inflation

Declining investment has hit kelp food companies particularly hard, since they’re also dealing with shrinking grocery-store revenues, especially for consumer packaged goods (CPG)—which includes most seaweed foods. Also, high inflation rates mean a seaweed snack or seasoning won’t do as well; when food prices are up overall, consumers are less likely to spend on foods that aren’t familiar.

Describing the current CPG market as “brutal,” Courtney Boyd, founder of AKUA kelp burger company, closed her operation this August. Boyd founded her kelp company in 2016, supported by GreenWave, and for a while it was thriving: She raised $4.5 million in funding from 2020 to 2024, according to Phyconomy. Looking back, Boyd regrets not having invested in farming, instead buying kelp wholesale from middlemen. She eventually began working directly with farmers in 2023, but it was too little, too late.

“With an inflationary environment, if you are a consumer-package company and you don’t have a lot of oversight in terms of what’s happening with the supply chain, you’re in trouble when times are challenging,” says Julia Paino of Desert Bloom Foods, a food investing firm.

Boyd’s company will be taken over by the Maine Family Seafarm Coop, run by Ken Sparta, one of Boyd’s partner farmers. The co-op plans to focus on direct-to-restaurant sales and piggyback off their existing oyster-selling infrastructure, avoiding the cost and complication of grocery-store sales entirely.

A Patchwork of Regulations

While investment in seaweed is lagging, so is America’s regulatory framework. Each state has its own rules around seaweed farming. In Maine, for instance, farmers can only operate on leases after a period of public comment followed by approval, and only if the leases do not interfere with existing maritime operations. In Alaska, seaweed farmers can only cultivate seaweed varieties that grow natively within 50 kilometers of their farm. In California, no regulatory pathway even exists for seaweed farming in state waters. All commercial seaweed farms are on land.

Unlike terrestrial farming, no federal laws govern or guide ocean farming. Nor is there any federal tracking of seaweed landings, despite the edible seaweed business being worth nearly $2 billion in the U.S. This stands in stark contrast to terrestrial farming: At any given time, a citizen can look up exactly how much of a crop is grown, to the acre, on the U.S. Department of Agriculture (USDA) website, going back to the 1900s. This information is intimately tied to subsidies like the farm bill, which provides support to American farming industries like corn, soy, or pork. Without the clear picture that tracking provides, it’s harder for money to flow.

In the case of seaweed, four federal agencies touch seaweed, but only lightly: the U.S. Army Corps of Engineers, whose regional offices are responsible for permitting every single seaweed farm in the U.S., but not for following up once those farms are established; the National Oceanographic and Atmospheric Administration (NOAA), which funds seaweed projects and education and tracks landings for fish and aquaculture, but not seaweed; USDA, which helps fund seaweed farms, on a limited basis, but doesn’t regulate them; and the U.S. Food and Drug Administration (FDA), which regulates imported seaweed products and domestic seaweed—but only if it’s part of a pharmaceutical product. The U.S. Coast Guard, responsible for mapping fisheries and other structures in the water, does not yet map seaweed farms.

With no single federal agency having oversight, and few guidelines on either the state or federal level, seaweed companies and farmers are left in limbo.

Sunken Seaweed, one of California’s two commercial seaweed farms, has dealt with limbo for years now. Farmer Torre Polizzi raises dulse—a rich, meaty-tasting red seaweed favored by health-conscious consumers for its nutritional properties—in tanks on Humboldt Bay, in Northern California. California has no permitting process for seaweed farms in state waters, which extend anywhere from 3 to 12 nautical miles from land—an unsurmountable distance for most farmers. So, Polizzi is unable to grow his seaweed in the ocean, although dulse is native to the nutrient-rich, cold Pacific.

“That is where 99.9 percent of companies hit a wall in this industry in California,” says Polizzi, the rush of pumped seawater humming in the tanks behind him. Each of his 10 tanks holds 1,200 gallons of constantly bubbling seawater, which tumbles the seaweed so it photosynthesizes more evenly.

Polizzi considers himself lucky to have found a home for his seaweed at all. He and his wife spent five years trying to find a location in California for their farm. They are able to pump saltwater from the ocean, crucial for a land-based seaweed company, through a relationship with Hog Island, the Northern California oyster restaurant and market, which already has a salt-water pumping permit for its oyster operation.

The California Coastal Commission, which oversees the permits, has not issued any new pumping permits in many years. In exchange for the seawater, Polizzi helps oversee a research bull kelp site for Hog Island, Greenwave, and The Nature Conservancy (permitted in the bay because it not commercial).

Even selling his fresh dulse and dried seaweed flakes at the local farmers’ market was a battle: It took Polizzi six months of petitioning California’s legislature to allow seaweed as a “cottage food,” saleable at farmers’ markets.

“We are here in California. We have some of the best marine science institutions in the world,” says Polizzi. “We have the ability and tech to create the cleanest [seaweed farms] in the world. But we can’t implement them.”

Seaweed at Scale

Most of America’s seaweed growers are small operations near the shore. Ocean Rainforest’s “seaweed island” is miles from land and dwarfs them by several degrees of magnitude. It does share a similar growing technique with smaller farms, setting out buoys that support horizontal lines, inoculated with kelp, that then sprout fronds and grow under the sunlight. Instead of a few lines, though, there are hundreds here, arranged in immense grids under the ocean surface.

As a research farm, Ocean Rainforest is testing various seeding methods, grow depths, and length and spacing of lines to create a model that’s efficient, economical, and replicable. They need to be able to monitor the site from shore and created an intricate buoy system so that they can see from the coast if anything disturbed their seaweed lines overnight or after bad weather. The company is also developing a harvesting machine that will reap the seaweed “using minimum cost and time.”

If this project, set in a federal Exclusive Economic Zone (EEZ)—a strip of water that can stretch from 3 to 200 miles offshore—is successful, other farms could begin putting buoys in EEZs as well. The U.S. boasts the most EEZs in the world, a whopping 3.4 million square miles. That’s a lot of ocean to potentially cultivate.

“There is no silver bullet when it comes to climate change, but seaweed can be part of that solution,” says Eliza Harrison, until recently the director of California operations at Ocean Rainforest. Proponents of open-ocean farming say large-scale operations in EEZs could fulfill sustainability goals that smaller farms closer to shore can’t: namely, substantial water bioremediation and enough raw material to supplant petroleum products in plastics and fuel. “Can you take this biomass that is naturally growing, can you cultivate it and then use it as a food and feed product, or use it as a way to improve people’s well-being?” says Harrison.

While smallholder seaweed farms can boost maritime economies and provide job alternatives to commercial fishing, the lower quantities they yield makes it difficult to justify millions of investment in infrastructure. Additionally, seaweed from smaller farms wholesales at around $1 to $2 a pound, according to industry experts, a price that’s not competitive in industries like plastics or textiles, where raw materials can start at $.70 (for PET polyethelene) or $.67 (for cotton) per pound. Large-scale farmed U.S. seaweed has yet to be marketed, but experts say that larger, automated-harvest farms could price their raw kelp more competitively, hitting below the $1 mark.

Replacing fossil fuel–derived plastics, a major contributor to global warming, with a climate-positive material like seaweed seems like a no-brainer. But some scientists have serious concerns about scaling up kelp farms. For one thing, huge kelp monocultures could threaten native kelp forests, responsible for drawing down a large portion of the world’s carbon—around 56 million tons annually, according to a new study by Plymouth Marine Laboratory. That’s equivalent to taking nearly 13 million cars off the road a year. Even more staggering, marine algae produces 50 percent of the world’s oxygen.

That threat has already surfaced in China, which farms most of the world’s kelp. In 2021, seaweed farming in the Northern Jiangsu Shoal, combined with warmer waters and human pollution, helped create green tides that sucked up oxygen and suffocated marine species for 81 days. Pests and bacteria infections are concerns, and so is the introduction of non-native seaweeds that could crowd out the native ones, or introduce new, disease-causing microorganisms. If the U.S. were to allow thousands of acres of farms in the EEZs, could that affect already suffering kelp forests in states like Maine and California?

These kinds of questions, and the fact that the industry is still new and evolving, say some experts, may explain why state and federal agencies and policymakers have been taking their time with guidelines. Rules laid down now could protect—or jeopardize—seaweed in U.S. waters. Those rules could also determine whether small seaweed farms will play an important and valued role in America’s future, or begin to vanish, replaced by ever larger farms, repeating the history of farming on land.

The Beginnings of a Roadmap for Kelp

Slowly, some regulations are starting to take shape. A few states are beginning to safeguard against potential monoculture impact on wild kelp stocks. In Alaska, a “50-50 rule” protecting seaweed diversity requires every farm to collect its reproductive tissue for breeding kelp from at least 50 different plants, within 50 kilometers surrounding the farm. Maine mandates that farmers cultivate seaweed strains that are native to the state.

There’s action at the federal level, too. A bill proposed in Congress in 2023, the Coastal Seaweed Farm Act, would direct the USDA and NOAA to establish an Indigenous seaweed farming fund to help Native Americans continue cultivating a food that has sustained them for thousands of years. The act would also create a joint study on how to responsibly scale seaweed in the U.S., and implement regulations based on those findings that would protect marine environments, measure the impacts and benefits of seaweed farming, and establish guidelines for monitoring farms.

Another bill, the Sustaining Healthy Ecosystems, Livelihoods, and Local Seafood Act—known as the SHELLS Act—proposes that the USDA create an office of aquaculture to promote funding, create regulations to guide the industry, and more. “The SHELLS Act is a crucial step toward enhancing U.S. food security and environmental sustainability through responsible aquaculture practices,” said co-sponsor Congressman Nicholas LaLota (R-NY) in an email. His district is home to the state’s first commercial seaweed farming operation and a thriving Indigenous seaweed farming co-op.

If passed, the SHELLS Act would create a federal body that could help seaweed farming could evolve responsibly; the Advisory Committee, according to language in the bill, would “acknowledge the history, use, and preservation of Indigenous and traditional aquaculture practices and ecological knowledge.” Mapping of seaweed farms—critical for maritime navigation and, potentially, wildlife corridors if large swaths of the country’s EEZs are cultivated—could become a requirement.

The bill might incentivize a new round of investors, since seaweed harvest could be tracked just as simply as corn or soy. And it might give small farmers a boost. “Shellfish harvesters and seaweed farmers play an essential role in our food supply, but historically they haven’t received the support they need to reach their full potential,” said Congresswoman Suzanne Bonamici (D-OR), the bill’s lead sponsor, in a press release. The SHELLS act, she said, “will help shellfish harvesters and seaweed farmers grow their small businesses while expanding blue carbon ecosystems that help address the climate crisis.”

The past two years have been undeniably difficult for the seaweed industry, says Julia Paino of food investor Desert Bloom Foods. However, she sees promise in this ocean crop; it reminds her of to how tofu came the U.S. in the 1980s. She would know—that’s when her father brought the unknown food to American shores with his company Nasoya, convincing thousands of Americans to try a very healthy, unfamiliar food that was immensely popular in Asia, and ultimately to build the platforms and infrastructure that enabled its success.

“There’s a lot of similarities … You have something that’s been around for hundreds and hundreds of years, right? This is not a novel ingredient source that was just created in the lab. This isn’t cultured meat. This is something that is steeped in significant cultural history, [with] a lot of tremendous health benefits, and now we know, also planetary benefits. It’s a matter of helping educate consumers, right?” says Paino. “So, there’s even more opportunity, I think, around what can be done with kelp. You’ll continue to see excitement across a lot of investors—hopefully coming from a more informed place of, ‘What is it? How is it grown? What’s the type of infrastructure you need for it to thrive and be successful?’”