Scientists at the USC Wrigley Institute for Environmental Studies on Santa Catalina Island, working with private industry, report that a new aquaculture technique on the California coast significantly increases kelp growth, yielding four times more biomass than natural processes.
The researchers used a depth-cycling approach—i.e., physically moving the macroalgae between deep nutrient-rich water at night and shallow depths within the photic zone during the day to optimize growth. An open-access paper on their work appears in the journal Renewable and Sustainable Energy Reviews. . . .
If it lives up to its potential, kelp is a more attractive option than the usual biofuel crops for two very important reasons. First, ocean crops do not compete for fresh water, agricultural land or artificial fertilizers. And second, ocean farming does not threaten important habitats when marginal land is brought into cultivation. . . .
However, farming kelp requires overcoming a few obstacles. To thrive, kelp has to be anchored to a substrate and only grows in sun-soaked waters to about 60 feet deep. But in open oceans, the sunlit surface layer lacks nutrients available in deeper water.
Marine BioEnergy invented the concept of depth-cycling the kelp, and USC Wrigley scientists conducted the biological and oceanographic trial.
The kelp elevator consists of fiberglass tubes and stainless-steel cables that support the kelp in the open ocean. Juvenile kelp is affixed to a horizontal beam, and the entire structure is raised and lowered in the water column using an automated winch.
Beginning in 2019, research divers collected kelp from the wild, affixed it to the kelp elevator and then deployed it off the northwest shore of Catalina Island, near Wrigley’s marine field station. Every day for about 100 days, the elevator would raise the kelp to near the surface during the day so it could soak up sunlight, then lower it to about 260 feet at night so it could absorb nitrate and phosphate in the deeper water. The researchers continually checked water conditions and temperature while comparing their kelp to control groups raised in natural conditions. . . .
Cindy Wilcox, co-founder and president of Marine BioEnergy, estimates that
it would take a Utah-sized patch of ocean to make enough kelp biofuel to replace 10% of the liquid petroleum consumed annually in the United States. One Utah would take up only 0.13% of the total Pacific Ocean.
The US Department of Energy’s Advanced Research Projects Agency-Energy invested $22 million in efforts to increase marine feedstocks for biofuel production, including $2 million to conduct the kelp elevator study. The Department of Energy has a study to locate a billion tons of feedstock per year for biofuels; Cindy Wilcox said the ocean between California, Hawaii and Alaska could contribute to that goal. . . .