Kelp could someday fuel ships and planes, but hurdles remain

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Green cells grown in a lab and whisked through bubbling water are intended to become fast-growing kelp—seaweed that researchers say could someday be processed into biofuel for ships and aircraft. The work is being pursued at the Woods Hole Oceanographic Institution, where marine scientists and engineers describe kelp as a potential alternative to petroleum-derived fuels that emit carbon dioxide when burned.

In the ocean, electricity from solar and wind can power cars, but ships and aircraft largely rely on liquid fuels made with a large percentage of oil or gasoline. Kelp-based biofuels are part of an approach to changing that fuel mix, including a pathway that uses heat and pressure—hydrothermal liquefaction—to convert organic material into fuel.

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

Kite-Powell, an engineer and economic analyst at Woods Hole, pointed to the broader challenge: moving from promising biology to a fuel supply chain requires more than laboratory progress. Aquaculture farms today remain small, supplying kelp mainly to restaurants, cosmetics companies and fertilizer producers, she said, while a kelp-biofuel market has not yet taken shape.

The effort has depended on federal support. In 2016, the U.S. Department of Energy launched MARINER—Macroalgae Research Inspiring Novel Energy Resources—with projects ranging from developing heat-resistant kelp to studies on seaweed genomes. The program’s work included breeding kelp with desirable traits, including strains with nonreproductive capabilities designed to prevent interbreeding with wild kelp.

Lindell’s MARINER funding lasted six years and finished in 2024. Since then, he said federal research opportunities have been fewer and delayed, though he argued the need for sustainable energy has not gone away. “I don’t think things have changed incredibly since the first oil crisis.”

Industry, however, has struggled to find the economic “middle market” that would link kelp farms to fuel demand. Oliver Dixon, a shellfish farmer based in Point Judith, Rhode Island, grows kelp to supplement his oyster operation during winter and said buyers have been inconsistent. “The buyers come in and out, it’s pretty discouraging,” Dixon said, noting his 9-acre (3.6-hectare) farm is far smaller than the scale that would be required for biofuel production.

Dixon expects to harvest about 10,000 pounds (4,500 kilograms) of kelp this month, selling most of it to local restaurants and seafood markets. Kite-Powell said scaling production would require sustained government support beyond the private sector, given how oil price volatility can spur interest while public support for alternative fuels can fluctuate.

Bren Smith, an ocean farmer and co-founder of GreenWave, argued the problem is not simply a lack of demand but where kelp makes sense economically. “We’ve made this mistake before, right?” Smith said, referring to large-scale investments in kelp research focused on fuel, and she said the fossil fuel industry is “the most technically advanced, subsidized industry on the globe,” making fuel a low-value use compared with products like cosmetics or food.

Even with a guaranteed buyer, scaling would face regulatory obstacles, according to Kite-Powell. In the United States, coastal waters are often prioritized for recreation, fishing and conservation, she said, making large aquaculture permits harder to obtain than in some Asian countries where seaweed farms can cover entire bays.

For now, U.S. farms tend to stay small and nearshore. Dixon said he cannot obtain a permit to keep his infrastructure in the water year-round, so he must remove lines and anchors each spring and reinstall them in the fall. Moving farther offshore could allow larger operations, but it also introduces engineering and environmental issues, including risks of entangling marine animals and uncertainty over whether 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 with those uncertainties, Lindell said his team remains focused on the long game, continuing to study and breed thousands of kelp strains with the goal of supporting a future biofuel industry.

Lindell said volatile fuel prices and the finite nature of oil point toward a transition. “We’ll come to the realization that things have shifted in the marketplace,” Lindell said, adding that “we can’t squeeze any more oil out of the earth in 30 years’ time.”