Seaweed finds growing demand, shows promise in climate change fight
On a picturesque summer day in Northern California, Max Rintoul, Lauren Kiino, and Gary Fleener, all with Hog Island Oyster Company, headed out on Tomales Bay for an exploratory harvest.
But on this day, it wasn't the oysters they were interested in. It was the seaweed.
"Seaweeds co-occur with shellfish on our farms, and together, they fit into - in this case - the healthy ecosystem of Tomales Bay," said Fleener, Hog Island's science and research director. "We're harvesting it because it's an abundant resource that historically has been viewed as a fouling organism; something that gums up the work at the oyster farm."
The seaweed growth is unintentional, says Fleener.
"In addition to oysters, this area is an incredibly productive habitat for seaweeds as well," he said. "It looks like it's being farmed intentionally, but the seaweeds just settle onto the gear, the ropes and baskets naturally."
"The perfect system for seaweed to grow on and under," Rintoul said. "The oyster is depositing nutrients below it, so that is kind of stimulating the growth of the seaweed, and it's also creating another habitat surface for the seaweed to actually settle on."
But up until recently, Fleener says they couldn't legally harvest the seaweed that grows on their oyster farm.
"We worked with the state to amend our permits to allow us to utilize those seaweeds," he said.
They primarily harvest the seaweed for use in Hog Island's restaurants.
"I like to use it in a fresh preparation - like a fresh herb," Kiino said. "We can use it pureed in a sauce - like instead of using parsley, we'd make a salsa verde with sea lettuce. We can also dehydrate it and do like dried parsley flakes and crust a fish with it. We can also chop it up and use it as a seaweed salad."
But Fleener is eager to get his hands wet for the sake of science and exploring environmental sustainability.
"There is a massive accumulation of seaweed biomass. If it's left here, it'll rot and that carbon will be released back into the atmosphere," he said. "Some of this is great as food. But, can we take some of this extensive biomass and utilize it up at our ranch, for example, to create perhaps a high-value soil amendment? Some kind of biostimulant?"
Fleener says they're working with a team of researchers from several California universities just awarded a California Sea Grant to study the seaweed or macroalgae that forms on shellfish gear, and what can come from it.
"These seaweeds present us with yet another pathway to harness the value of these farms," he said.
Zooming out from Fleener's focus, there is a lot of momentum right now for research about harvesting seaweed, its potential uses, and its impacts on climate change.
"In terms of climate change and carbon capture, it's amazing. Seaweeds grow extremely fast - meters a day, some of the kelps, they grow meters a day," said Jackson Gross, an aquaculture specialist at the University of California, Davis. "People have been looking at ways to rapidly harvest kelps and seaweeds and then figure out ways to take that carbon and then do something else with it."
Luke Gardner, a research faculty member at San Jose State University's Moss Landing Marine Laboratories and an aquaculture specialist with California Sea Grant, says there is a lot of promise about seaweed, but little data to cite so far.
"We're just starting to discover seaweed aquaculture in the U.S. and California. It can be a very low-impact way of producing resources that we need, whether it be food or things like biomaterials," said Gardner. "I definitely think one of the exciting things about seaweed is all that stuff we don't know about yet."
Early research shows promise, however. Take ogonori - ogo for short, a type of seaweed used in Asian and Hawaiian cuisines, as an example grown at industrial scales elsewhere in the world.
"One of the other things that we found about this species is that it has some potential to reduce the methane emissions from cattle," said Gardner. "Methane is a climate pollutant. It doesn't last as long as CO2 but it's about 25 times more potent."
Gardner says figuring out more ways to use seaweed will help give people an economic reason to grow it. One of the simplest ways to make that happen? Americans are eating more of it.
"I think that would go a long way to producing more seaweed which likely has a bunch of climate benefits and ecosystem services," he said.
Fleener is excited to be exploring what may be part of a sustainable and nutritious future.
"At Hog Island, we believe that the foods we're producing provide a great way to have what we eat be a positive force for good - in terms of climate change," he said. "Partnering with our research associates is really, a way that we can bring a broader set of eyes and experiences to solving some of the problems and questions we have about what happens on our farms."