Electricity from solar and wind energy can power cars, however ships and aircraft largely run on liquid fuels made with a large percentage of oil or gasoline. When burned, those emit carbon dioxide, a greenhouse gas that causes global warming. Biofuel, refined from organic material like plants or algae, is a potential option to change the fuel makeup.

One kind of biofuel comes from kelp. Through a process that uses heat and pressure to produce fuel, known as hydrothermal liquefaction, this humble seaweed could power ships and aircraft without any petroleum.

“We need other sources of energy that are sustainable, we can’t just rely on petroleum,” said Scott Lindell, a marine scientist at the Woods Hole Oceanographic Institution about a 90-minute drive south of Boston. “There’s hardly anything simpler, or anything that grows quite as fast and as sustainably, as seaweed.”

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EDITOR’S NOTE: This story is a collaboration between the MIT Graduate Program in Science Writing and The Associated Press.

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Existing biofuels, like corn-derived ethanol, primarily work as gasoline additives. Corn crops require agricultural land, fresh water and pesticides while kelp, by contrast, can be grown in the ocean with minimal resources.

Although any bioethanol — whether produced from corn or kelp — releases hazardous gases when burned, such as acetaldehyde, these fuels produce fewer greenhouse gases overall compared to petroleum-based fuels.

Researchers like Lindell have successfully bred kelp varieties that in some cases produce up to three times more biomass than conventional strains. Yet energy companies are hesitant to invest in large-scale aquaculture projects without demonstrated demand, and farmers are reluctant to scale up without a guaranteed buyer, forming a circular problem that has slowed industry development.

Government interest in biofuels is inconsistent

Aquaculture farms today remain small, supplying kelp primarily to restaurants, cosmetics companies and fertilizer producers. Hauke Kite-Powell, an engineer and economic analyst at Woods Hole, said scaling kelp production to support a biofuel economy would require sustained government support, beyond just the private sector.

While oil price volatility, driven in part by international conflicts such as the war in Iran, has led to bursts of renewed interest in energy independence, government support for options like biofuel fluctuates in the United States. In 2016, a program run by the Department of Energy set out to develop tools for kelp-based biofuel production.

The program, known as MARINER — Macroalgae Research Inspiring Novel Energy Resources — consisted of projects ranging from developing heat-resistant kelp strains that can withstand warming oceans to studies on seaweed genomes. The Department of Energy often backs exploratory, high-risk high-return projects, and researchers involved in MARINER said they made progress, such as increasing kelp yields.

The program mirrored a similar feasibility-testing venture that began in the 1970s, which was swiftly terminated once oil prices stabilized. Lindell’s lab, funded by MARINER, focused on improving crop yield by selectively breeding kelp with desirable qualities — such as nonreproductive capabilities to prevent interbreeding with wild kelp — so that, down the line, farmers could scale up their kelp production.

Lindell’s MARINER funding lasted six years, finishing in 2024. Since then, federal research funding opportunities have been fewer and delayed. But the urgent need for sustainable energy remains, he said. “I don’t think things have changed incredibly since the first oil crisis.”

A middle market for kelp has yet to materialize

Farmers note the difficulties of finding consistent kelp buyers. Oliver Dixon, a shellfish farmer based in Point Judith, Rhode Island, grows kelp to supplement his oyster business during the winter. As of this month, he expects to harvest about 10,000 pounds (4,500 kilograms) of kelp, selling most of it to local restaurants and seafood markets.

“The buyers come in and out, it’s pretty discouraging,” Dixon said. His 9-acre (3.6-hectare) farm is hundreds of times smaller than what would be needed to produce biofuel, and without proven demand from the energy sector, he has no plans to expand.

Bren Smith, an ocean farmer and co-founder of GreenWave, a nonprofit supporting ocean farmers, argues that the issue isn’t a lack of demand, but instead where kelp makes sense economically: Kelp is currently more viable in products like cosmetics or food, rather than fuel, which remains one of its lowest-value uses.

“We’ve made this mistake before, right?” Smith said, referring to large-scale investments in kelp research focused on fuel production instead of the seaweed’s myriad other uses. “Competing with the most technically advanced, subsidized industry on the globe, the fossil fuel industry.”

Red tape slows expansion, but researchers bet on the long game

Even with a guaranteed buyer, expanding kelp farming would face regulatory hurdles, according to Kite-Powell. In the United States, coastal waters are largely prioritized for recreation, fishing and conservation, making it difficult to obtain permits for large aquaculture projects. By contrast, countries in Asia often prioritize extensive seaweed farms, sometimes covering entire bays.

For now, most U.S. farms remain small and nearshore. Dixon said that he cannot obtain a permit to keep his farm infrastructure in the water year-round, requiring him to remove his lines and anchors each spring and reinstall them in the fall.

Moving farms further offshore could allow for larger operations, but it introduces engineering and environmental challenges, including the risk of entangling marine animals and the possibility that farmed kelp could compete with other marine life for nutrients.

“We don’t yet have a full understanding of what all the ecological side effects of very large-scale ocean farming might be,” Kite-Powell said.

Even so, scientists like Lindell remain confident that their work will be applied to a biofuel industry in the future. Around Lindell’s lab are glass vials and flasks of over 2,600 strains of sugar kelp collected from across New England, which he continues to study and breed selectively in hopes of the energy industry transitioning to renewable sources. To him, volatile fuel prices and the finite nature of resources like oil point to an eventual change.

“We’ll come to the realization that things have shifted in the marketplace,” Lindell said, “and we can’t squeeze any more oil out of the earth in 30 years’ time.”