Surf-Inspired LA-Brand Debuts A Shirt Made With Yarn From Seaweed

Outerknown's new Blanket Shirt made with a seaweed-based fiber.

LA-based clothing brand Outerknown is making shirts out of seaweed fibers. Working alongside North Carolina-based Keel Labs, the company is launching this week its most coveted item, The Blanket Shirt, with a new blend of fibers: 70% regenerative organic cotton (ROC) and 30% Kelsun, a seaweed-based fiber. It’s the first-of-its-kind, says John Moore, Co-Founder and Creative Director of Outerknown.

“Outerknown is a brand founded by surfers with the ocean always top of mind, so Keel Labs' work with seaweed-based fibers instantly resonated with us when we learned about it,” he says.

Kelly Slater, who started the company with Moore, adds, "The Blanket Shirt was one of the first products in our line, and it remains one of my favorite pieces. It’s been ten years since we made the first one, and we are proud to be partnering with Keel Labs on the next generation of this shirt with a version made of 100% bio-based fibre derived from seaweed. Working with suppliers that share our love for the ocean is a great fit for Outerknown. I’m excited to see this grow.”

Kelsun Fiber made from seaweed by North Carolina-based Keel Labs.

In an industry that produces 21 billion tons of textile waste annually, says CEO and Co-Founder of Keel Labs Tessa Callaghan, Kelsun wants to function as an alternative to conventional, resource-intensive materials (think conventional cotton).

“What we do is work with a known polymer that is derived from brown seaweed. It's called alginate. We take that alginate and we create a formulation that then allows it to enter into existing fiber manufacturing systems. We create regimented rules where we do not use toxic chemicals throughout any of our processes. Everything we use and then end up producing and selling must be 100% biodegradable.”

Keel Labs sources seaweed that’s harvested under strict sustainability guidelines, complying with local harvesting calendars and quantities, Callaghan explains. A biopolymer is then extracted and separated from the seaweed, forming the basis of Kelsun fibres. The seaweed is harvested from various locations in South America, and processed in North Carolina.

But is all seaweed OK to use? Callaghan notes there are differences.

“The majority of all seaweeds are either farmed or wild-caught. A small percentage of them is what we don't want to do, which is basically tearing up the root from the environment that it's growing out of. Trimming it is okay. Catching it once it's already waste on the beach and ends up kind of harming the ecosystem that way is okay. Farming through vines, which is really standard, is also great. But we really need to be making sure that especially as production rates grow, not just for us but for any industry, that we're continuing to monitor the positive and negative impacts that it can have on a region because there are capacities.”

For Outerknown, that Kelsun fiber is then sent to their mill in Portugal, where it meets the regenerative organic cotton (coming from India). The mill uses the two types of yarn to weave the fabric. And lastly, that undyed fabric is sent to a nearby facility, also in Portugal, for it to be cut, sewn, and washed into garments using mineral dye.

Yes, the material is more expensive at this time, admits Kirsten Araville, Director of Supply Chain at Outerknown. “The cost is still relatively high during the proof-of-concept phase, but we’re confident that as more brands adopt the fiber, it can be scaled, making it more cost-effective over time.”

Outerknown's best-selling Blanket Shirt made with Kelsun fiber.

There are also a few limitations with the dying, notes Moore. “Lighter colors and gentle dyes, like mineral dyes, seem to be work best with this fiber, which is why we chose to launch in a ‘Muted Plum’ colorway. It’s a soft, faded purple that’s having a moment right now. What’s interesting is that we originally selected this color a year ago because it was a design room favorite, and then a similar hue appeared prominently at the Paris Olympics, like on the athletics track. While the fiber works well with a wide chromatic spectrum, we believe innovation—especially responsible innovation like Kelsun—should never limit us from creating timely, compelling products.”

Althought this Blanket Shirt is available in limited quantities, the Outerknown team is looking at how they can add Kelsun to other products, says Araville. “The seaweed is processed to simulate the feel of cotton, resulting in a soft, lightweight material. While still in the R&D phase, we've already found ways to integrate it into knits and sweaters.”

So in conclusion, it begs the question, is seaweed fiber better? And if so, better than what?

Callaghan explains that the answer is a bit complex. Not one fiber is perfect. While cotton is a natural fiber, it too can be resource-intensive (irrigation, pesticides, and fertilizers, especially if grown conventionally). Meanwhile, polyester sheds microplastics, which have been damaging for the environment. So on a spectrum, Callaghan notes that this seaweed-based fiber requires fewer inputs (not taking away land used for food farming and lots of water to irrigate crops), sequesters carbon, is free of toxic chemicals, and most of all, is biodegradable.

In fact, the Blanket Shirt is 100% biodegradable because its a cotton-Kelsun blend. So, it helps fashion companies enter an era of circularity and reduce waste.

Keel Labs has raised just under $18 million to innovate in the natural textile space. While a significant fundraise, “it is a drop in the bucket,” notes Callaghan compared to other tech-based companies. That said, she hopeful that this could be the start of a new materials stream for the textile industry, giving manufacturers more options for toxic-free biodegradable fibers.

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