Planes and ships could one day run on fuel derived from kelp, a type of seaweed, but significant obstacles remain before this vision becomes a reality. In laboratories, tiny seaweed cells called gametophytes are cultivated in red-light chambers, part of a former U.S. government-funded initiative to develop sustainable biofuels for transportation.
The Promise of Kelp Biofuel
While electric vehicles can be powered by solar and wind energy, ships and aircraft largely depend on liquid fuels derived from oil or gasoline. Burning these fuels releases carbon dioxide, a greenhouse gas contributing to global warming. Biofuels, refined from organic materials like plants or algae, offer a potential alternative. Kelp, through a process known as hydrothermal liquefaction, can be converted into fuel 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 in Massachusetts. “There’s hardly anything simpler, or anything that grows quite as fast and as sustainably, as seaweed.”
Challenges Compared to Corn Ethanol
Existing biofuels, such as corn-derived ethanol, are primarily used as gasoline additives. Corn requires agricultural land, fresh water, and pesticides, whereas kelp can be grown in the ocean with minimal resources. Although any bioethanol releases hazardous gases like acetaldehyde when burned, these fuels produce fewer greenhouse gases overall than petroleum-based fuels. Researchers like Lindell have successfully bred kelp varieties that yield up to three times more biomass than conventional strains. However, energy companies hesitate to invest in large-scale aquaculture without demonstrated demand, and farmers are reluctant to scale up without guaranteed buyers—a circular problem hindering industry development.
Inconsistent Government Support
Aquaculture farms remain small, supplying kelp mainly to restaurants, cosmetics companies, and fertilizer producers. Hauke Kite-Powell, an engineer and economic analyst at Woods Hole, said scaling kelp production for biofuels would require sustained government support beyond the private sector. Oil price volatility, driven partly by international conflicts like the war in Iran, has spurred periodic interest in energy independence, but U.S. government support for biofuels fluctuates.
In 2016, the Department of Energy launched the MARINER program (Macroalgae Research Inspiring Novel Energy Resources), which included projects on heat-resistant kelp strains and seaweed genomics. Researchers involved reported progress, such as increased kelp yields. The program mirrored a similar feasibility-testing venture from the 1970s, which was terminated when oil prices stabilized. Lindell’s lab, funded by MARINER, focused on improving crop yield through selective breeding, including nonreproductive strains to prevent interbreeding with wild kelp. The funding ended in 2024, and since then, federal research opportunities have become fewer and delayed. “I don’t think things have changed incredibly since the first oil crisis,” Lindell said.
A Missing Middle Market
Farmers struggle to find consistent buyers for kelp. Oliver Dixon, a shellfish farmer in Rhode Island, grows kelp to supplement his oyster business in winter. He expects to harvest about 10,000 pounds (4,500 kilograms) this month, selling mostly 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 for biofuel production, 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 kelp is currently more economically 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 instead of other applications. “Competing with the most technically advanced, subsidized industry on the globe, the fossil fuel industry.”
Regulatory and Ecological Hurdles
Even with a guaranteed buyer, expanding kelp farming faces regulatory barriers. In the United States, coastal waters are primarily prioritized for recreation, fishing, and conservation, making permits for large aquaculture projects difficult to obtain. In contrast, countries in Asia often prioritize extensive seaweed farms, sometimes covering entire bays. Most U.S. farms remain small and nearshore. Dixon cannot obtain a permit to keep his farm infrastructure in the water year-round, requiring him to remove lines and anchors each spring and reinstall them in the fall.
Moving farms offshore could enable larger operations but introduces engineering and environmental challenges, including the risk of entangling marine animals and competition 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.
Long-Term Optimism
Despite these hurdles, scientists like Lindell remain confident that their work will eventually support a biofuel industry. His lab contains over 2,600 strains of sugar kelp from New England, which he continues to study and breed selectively. He believes volatile fuel prices and the finite nature of oil will drive a market shift. “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.”
