Outerknown’s newest shirt is made from seaweed

If you pick up a new shirt from Outerknown without looking at the label, you might assume it’s made from cotton. But it’s actually partially made from seaweed. The clothing, a limited-edition run of the brand’s popular Blanket Shirt, is the first commercially available item made from a blend of cotton and Kelsun, a kelp-based fiber. It will go on sale on September 24. [Photo: courtesy Outerknown] Why seaweed? It’s a more sustainable raw material than the fossil fuels that go into synthetic fabric, or even natural fibers like cotton. “It doesn’t need to be watered,” says Aleks Gosiewski, cofounder and COO of Keel Labs, the startup that developed the material. “It doesn’t need to be fertilized, which is a huge reduction in impact relative to some natural fibers.” [Photo: Ryan Duffi/courtesy Outerknown] Cotton, by contrast, requires large amounts of water: Around 2,600 gallons can go into growing the amount needed for a single pair of jeans. As climate change progresses, farmers are using more water. Extreme heat and other climate impacts are also making it harder to keep the crop alive. Most cotton is grown with synthetic pesticides and polluting fertilizer. (Organic cotton doesn’t use problematic chemicals, but only makes up a tiny fraction of global production.) Cotton also uses land that might otherwise be used for growing food or forests. Seaweed avoids these challenges, while also capturing large amounts of CO2. “Our brand was founded by surfers, and the ocean is always top of mind, so when we learned about Keel Labs’ work with seaweed-based fibers, it immediately resonated with us,” says John Moore, creative director at Outerknown who cofounded the company with pro surfer Kelly Slater. [Photo: Outerknown] The company was already moving its organic cotton products to “regenerative” organic cotton, a product that’s certified for taking extra steps to benefit the environment, such as no-till farming and composting. The seaweed fabric had similar properties to cotton and could be blended with cotton yarn, creating a lightweight, extra-soft version of the shirt. (The new shirts are made from a blend of 70% regenerative organic cotton and 30% Kelsun, because of the current limited supply of the seaweed-based material.) Keel Labs sources brown seaweed that’s harvested from coastlines in places like South America, and then extracts biopolymers to make its material. The polymers are extruded through tiny holes to make fibers, and processed without toxic chemicals. Some other materials, like bamboo, require hazardous chemicals to turn into fabric; seaweed, which breaks down more easily, can avoid that. [Image: courtesy Outerknown] The fibers go to factories and mills to be spun into yarns and knit or woven into textiles. Then they can be sent through the rest of the supply chain for dyeing and sewing into garments. The fabric can be tweaked based on what a fashion brand needs. “That’s where the designers from all these different teams come into play,” says Gosiewski. “You can create a really fine yarn. You can create a really chunky yarn. You can make, as a result, varying fabrics with different textures and then different final goods from those materials in apparel, home goods, or other applications.” [Photo: Ryan Duffi/courtesy Outerknown] It took time to develop a commercial garment. “Being at the forefront of innovation always presents a learning curve,” says Outerknown’s Moore. “We went through multiple rounds of trial and error to get the right blend, construction, and quality that matched our Blanket Shirt. We also conducted wash and drying tests to ensure it performed similarly to our current [regenerative organic cotton] construction. This process takes time and is costly, especially since pioneering something new means working through every challenge with our suppliers.” Keel Labs, which launched seven years ago when Gosiewski and cofounder Tessa Callaghan began looking for more sustainable options for materials while students at the Fashion Institute of Technology, is still at a very early stage. Kelsun, their material, is more expensive than conventional fabrics, since production hasn’t yet scaled up. It’s not clear exactly how much it will be able to replace other materials. But seaweed production continues to grow, and because of seaweed’s climate benefits, other companies are working on new methods that can help increase seaweed farming more. The startup believes that seaweed-based fabric can become a mainstream material. “These feedstocks provide volumes that allow us to produce enough Kelsun to be a lasting, reliable fiber option to the masses,” says Gosiewski.