Off the coast of Catalina Island near Los Angeles, a prototype of a new “kelp elevator”–a long tube with seaweed growing on it that can be moved up and down in the water to access sunlight and nutrients–will soon begin tests.

If the study works as hoped, the startup behind it, Marine BioEnergy, wants to use similar technology, driven by robotic submarines, to begin farming large tracts of the open ocean between California and Hawaii. Then it plans to harvest the kelp and convert it into carbon-neutral biocrude that could be used to make gasoline or jet fuel.

“We think we can make fuel at a price that’s competitive with the fossil fuel that’s in use today,” says Cindy Wilcox, who cofounded Marine BioEnergy with her husband Brian Wilcox, who manages space robotics technology in his day job at NASA’s Jet Propulsion Laboratory at California Institute of Technology.

Other biofuels, such as ethanol made from plant waste on corn fields, have struggled to become commercially viable, particularly after oil prices crashed. Solazyme, a company that planned to make biofuel from algae (and predicted in 2009 that it would be cost-competitive with fossil fuels within two or three years), ended up pivoting to make food products under the name TerraVia, and has now declared bankruptcy.

Kelp might have a chance of faring better. Unlike plants on land, it has little lignin or cellulose, fibers that make processing more difficult and expensive. In the right conditions, it can grow more than a foot a day, without the need for the irrigation or pesticides that might be used on land.

A key to the company’s concept is farming in the open ocean, where there is room to grow vast quantities of kelp. “You’re going to need a lot of kelp in order to make it cost-competitive with something like coal, fossil fuels, or natural gas,” says Diane Kim, a scientist at the University of Southern California’s Wrigley Institute for Environmental Studies, which is helping run the proof-of-concept study of Marine BioEnergy’s technology at Catalina. “In order to grow that much kelp, you really have to move outside the normal range of where kelp is found, which is along the coast.”

Kelp doesn’t typically grow in the open ocean since it needs both sunlight found near the surface of the water and nutrients that are found near the ocean floor (it also needs to anchor itself to something). In the 1970s, during the oil embargo, the U.S. Navy began investigating the possibility of farming kelp in the open ocean, pumping deep ocean water filled with nutrients to kelp anchored near the surface. But anchors often failed in ocean currents, and after the embargo ended, government interest faded.