Consumer obsession with athleisure wear, which has only accelerated during the pandemic, is taking a toll on the environment, and Allbirds is the latest retailer tackling the problem by rethinking materials.

Today, the San Francisco-based retailer known for its sustainable sneakers released a new line of workout clothes, including leggings, shorts, tanks, and T-shirts, made from materials like eucalyptus tree fiber and merino wool. Called the Natural Run Collection, co-founder and CEO Tim Brown says the line, which took two years to develop, intends to yoke human health and planet health in a move away from polyester blends.

According to a recent report from the Circular Fibres Initiative, 55 percent of all clothing is made with polyester, a durable and waterproof synthetic fiber that is cheap to produce and perfect for a sweat-wicking shirt or stretchy pair of yoga pants. But because polyester is made from petroleum and crude oil, its annual production puts 700 million tons of carbon into the atmosphere each year. Its sustainability issue is further complicated by its disposal, as polyester's fibers break down into smaller and smaller particles that eventually make it into the ocean. An estimated 14 million tons of these microplastics already have.

Brown, who was a professional athlete for over a decade, has spent a good amount of time in synthetic exercise apparel. "After starting Allbirds, I hoped that there was a better way to make the things we work out in, one that relies more on nature, rather than simply defaulting to all oil-based fibers," says Brown. In 2020, the company announced a goal of using 75 percent natural or recycled materials in everything Allbirds manufactures by 2025.

Allbirds is in good company in its race to become the sustainable workout retailer of choice. The field, which includes environmentally focused Patagonia, grows every year. For example, Seattle-based Girlfriend Collective recycles plastic water bottles into yoga pants and sports bras. Certain outerwear pieces by British designer Stella McCartney are made with a recycled yarn called Econyl, which is created with carpets, waste fabric, and fishing nets collected from the oceans.

In addition to rethinking materials, Allbirds is labeling the carbon footprint of each of its items, ranging from 4.7 kg to 14.5 kg CO2e, before neutralizing the footprint with carbon offsets. Allbirds already does this for its shoes, but claims it's the first company to offer the carbon labeling for workout apparel. Looking forward, Allbirds is reportedly seeking a $2 billion valuation for an IPO as soon as September, after having raised a $100 million Series E last year, Bloomberg reported earlier this summer.