Bay Area startup looks to seaweed as a possible solution to plastic pollution

CBS News

07-03-2025

Plastic waste is a huge problem, with bags and packaging a major culprit. A Bay Area startup has figured out a way to replace these plastics, with a plant that grows abundantly off the coast.
At the Fitzgerald Marine Reserve in Moss Beach in San Mateo County, twice a day, at low tide, a sensational event unfolds.
The giant Pacific waves recede to reveal a hidden world, teeming with marine life. Growing on the giant rocks, glistening seaweed.
The countless species of marine plants and algae are arguably one of Mother Nature's miracle crops.
"Seaweed does a lot of good while it is growing. It's creating habitat for biodiverse life, it's creating every other breath that you take, it's sequestering an immense amount of carbon. There's lots of reasons to love seaweed," remarked entrepreneur Julia Marsh.
Now there's a possible remarkable new one at Sway, a San Leandro-based startup.
"At Sway, we're using seaweed as a replacement for plastic," said Marsh.
"Our material is 100% compostable in both a home and industrial setting," added Matt Mayes.
Marsh and Mayes are the co-founders of the startup. Using breakthrough technology, they've come up with a promising solution to a huge problem.
"We're using the natural polymers which is the plastic-like quality of seaweed to replace flexible films and bags and wrappers and pouches that are causing so much pollution on our planet," explained Marsh.
Seaweed contains high levels of a certain substance – a natural polymer - that makes it stretchy and flexible.
Using that polymer, the team created what it calls "Thermoplastic Seaweed Resin," or TPSea for short. TPSea is a bio-based resin that melts and stretches just like plastic.
The beauty of the breakthrough is that it can be used in existing plastic manufacturing systems.
The Sway team showed CBS News Bay Area how the TPsea worked with blown film extrusion.
"So, this is a very small-scale version of what's being done in industry. So, imagine this but 5 stories tall and a bubble that's like 80 inches wide," explained Senior Material Engineer Matt Catarino.
Catarino placed a handful of pellets into the device, which created a very thin-walled film made from the seaweed formulation.
"This is one of the most difficult processes for plastic extrusion, and to be able to say we're doing seaweed on it, it's pretty cool." said Catarino.
"There is a big issue with fossil-based plastics, and this is kind of almost a catch all for a material that can change the industry and impact our earth in a fantastic way," said materials Engineer Vincent Hoey.
The formulations are also home compostable and non-toxic according to lab manager Annie Wang. She was working on collecting and verifying the data on composting.
"The home composting certification tests looks for breaking down within 180 days and this is showing almost full disintegration of our material in these elevated conditions in 2 to 3 weeks," said Wang, pointing to frames full of disintegrating films.
You can find sway's seaweed formulations in food windows, product wrappers, and polybags. The polybags are in use by clothing brands, including Faherty, Alex Crane, Florence, and Prana.
"Our vision, our mandate our goal is to include as much seaweed and as much bio-based content as possible into all the products we're offering," noted Mayes.
Sway sources its seaweed from farms around the world including Indonesia and Maine.
The cultivated crops don't require fresh water or fertilizers and grow quickly.
"The most common method is you have these lines that are seeded with seaweed you give the seaweed a haircut. When it's time, the seaweed regenerates," explained Marsh.
Back at Moss Beach, CBS News Bay Area asked visitors what they thought of the idea.
"What better way is that to use the seaweed/ i think that's great. You know what i mean? That's awesome", said East Bay Resident Deborah Yabusaki.
Eileen Field liked the idea that it was home compostable.
"I have a farm, I have a mandarin orchard, and of course we're always trying to make compost for the trees so I think that would be awesome", Field said.
Eleven million tons of plastic enter the ocean every year. The team at Sway hopes to turn that around.
"If there's more seaweed, the ocean's a healthier place. The planet's a healthier place," said Marsh, with a big smile.