The luxury fashion world has its eyes on mushroom leather. Hermès announced a reimagining of its Victoria travel bag made from it, albeit with elements of calfskin. And Adidas announced Stan Smith sneakers made from the supple, leather-like material. But, what is mushroom leather, how sustainable is it? And does mushroom leather stand up to the quality of genuine cowhide leather?
What is mushroom leather made from?
“Mushroom leather” sounds like something made from the caps of portobellos, but it’s actually made from mycelium, the lattice-like root network of fungi. (Mushrooms are the fruit of mycelium.)
This sprawling network of fungal roots threads its way through soil and old tree trunks, playing a critical role in breaking down organic matter to provide nutrients to nearby plants.
“Imagine the branches and vines that grow apples or grapes,” Jamie Bainbridge, vice president of product development at Bolt Threads, a biotechnology company that makes mushroom leather, tells LIVEKINDLY. “Mycelium functions like those twisting, branching supports just under the surface. It brings sustenance to all living species and is the literal world wide web.”
Mycelium do indeed function as an organic information superhighway, developing underground networks that plants use to talk to each other. It can even strengthen plants’ immune systems by triggering the production of defensive chemicals.
That fact alone is mindblowing. But there’s more: mycelium can help humankind lower its carbon footprint, from the food we eat and the products we buy, the homes we build, and the packaging, too. This includes mycelium-based leather, colloquially referred to as “mushroom leather.”
The environmental impact of leather
Leather production has a massive carbon footprint. Cowhide is a co-product of the beef and dairy cattle industries, which account for 60 percent of all greenhouse gas emissions generated by livestock, according to the Food and Agriculture Organization of the UN.
As Good on You describes, the distinction between a by-product and a co-product is that the latter is considered “desirable secondary goods.” This means that the animal hides are used to create goods for profit, rather than for waste reduction.
The livestock industry is a key driver of deforestation, directly linked to the loss of natural ecosystems. The Amazon rainforest is a prime example of this; much of the land has been cleared for cattle grazing or animal feed.
Animal skins also must be processed before being turned into consumer goods. This processing stage includes “tanning,” which alters the protein structure of the skin to make it less prone to breaking down or rotting. Leather can be tanned using vegetable tannins, polymers like Melamine, aldehyde, and chromium, which is the most common method.
Chromium, which has been classified by the FDA as a carcinogen for both humans and animals, comes with a host of risks and complications. The solid and liquid waste from tanning leather with chromium is often dumped into local water systems. This wreaks havoc on aquatic life in those areas and poses a major threat to humans.
Common side effects of chromium exposure include respiratory issues, infections, birth defects, and lung cancer. Tanning industry workers also risk developing skin ulcerations called “chrome holes” that do not heal, Gizmodo reports. Cheap labor and low environmental protections have made China, Bangladesh, and India the primary regions for leather tanning.
How is mushroom leather used in fashion?
Mushroom leather has already caught the attention of the fashion industry, and two major players have emerged in the space: Bolt Threads and MycoWorks, both of which are based in California.
In October 2020, Stella McCartney, Adidas, and Kering (The parent company of Gucci, Yves Saint Laurent, and other luxury brands) formed a consortium with Bolt Threads, granting the brands exclusive access to its mycelium-based leather called Mylo.
With the consortium formed, the involved brands will launch products made with Bolt Threads’ leather-like material. McCartney unveiled a Mylo leather bustier and balloon-style pants set in order to showcase the versatility of the material, while Adidas launched a version of its iconic Stan Smith sneaker crafted with Mylo leather.
Durability and quality are front and center, Bainbridge adds. “Our goal is to create a long-lasting, high-quality leather alternative material that provides the level of durability that customers have come to expect.”
Input from its consortium partners, like Adidas, is critical to helping to achieve this goal. The global sportswear brand has been “receiving and working with material samples over time, providing critical feedback in the development process to help give Mylo material the strength and performance it demonstrates today on display in the Stan Smith Mylo.”
MycoWorks is also entering the luxury fashion space. The San Francisco-based biotechnology firm uses Fine Mycelium, a patented process used to craft various forms of vegan leather, called Reishi. (Reishi is named after a brown, fan-shaped mushroom used in Chinese traditional medicine.) These include Brown Natural, which has an amber hue and natural finish and Black Emboss, which has an ebony finish and pebble grain. AgFunder, a San Francisco-based venture capital firm that focuses on sustainable food and biotechnology, is among the company’s investors.
MycoWorks also exclusively developed a mycelium-based leather called Sylvania for French fashion house Hermès. The high-end label will launch a version of its Victoria bag made primarily of Sylvania and with elements of canvas and calfskin. The luxe vegan leather is grown in California and is then finished by Hermès in France to refine its durability.
So, how exactly is mushroom leather made?
Mass production of mycelium requires optimal conditions. Mushrooms are picky like that. So, to produce mycelium, manufacturers must recreate what happens in the forest floor, but in a controlled indoor environment. In nature, fungi biodegrade carbon-based matter. In its California-based facility, Bolt Threads starts by putting mycelial cells in a tray and then feeding them sawdust and other organic materials while controlling temperature and humidity. The fibrous roots then self-assemble into a large, foamy layer — “Imagine a big bag of smashed marshmallows,” says Bainbridge.
Once the mycelium is harvested, the remaining material is composted, and the sheet is processed and finished into Mylo, which can be used to make shoes, bags, wallets, phone cases, and other goods.
Bainbridge says that Mylo is ”substantial, supple, and soft. It has an unmistakable resemblance to leather, but with an unbelievably low impact. It can be used like animal or synthetic leather, and isn’t constrained by pattern or texture.”
MycoWorks makes Reishi through a similar process. Like Mylo, Reishi grows trays in a controlled environment and feeds on organic matter, like sawdust. The interlocking mycelium then grow into dense, durable sheets. MycoWorks then tans these sheets to produce finishes that imitate the various types of leather.
These two companies claim that mycelium leather is as durable and functional as cowhide leather. And, the fashion industry may soon have another option available for use. In Bandung, West Java, a biotech startup called Mycotech Lab developed its proprietary vegan leather using a process inspired by tempeh, a traditional Indonesian food made from fermented soybeans.
The process starts with the growth medium made from agroforestry-waste such as sugarcane, sawdust, coconut husks, and rice husks. Then, they play the waiting game. The mushrooms and mycelium grow for approximately a month before being harvested and processed into Mylea. It’s very similar to the tanning process of the conventional leather industry. But, “the difference is that we do not use any harmful chemicals in the process,” the business development and health, safety, and environment team of Mycotech Lab tells LIVEKINDLY. The company uses local, natural dies instead. And, it is working with a local business to transform the leftover mushroom-growing substrate into a pre-compost for fertilizer.
Mycelium-based leather has incredible potential benefits for the planet and for animals. It takes about two years for a cow to grow to the point where their hide can be turned into leather, whereas sheets of mycelium are grown in a matter of weeks. It’s also “It’s also “infinitely renewable,” says Bainbridge.
The process is chromium-free, eliminating the hazards that this chemical poses for the environment and the people who tan it.
Mycelium leather is not alone in taking on the behemoth of the leather industry. (And PU and PVC leather, which are made from plastic polymers and contribute to the microplastics problem, are no longer the only alternatives.) Vegan leather can now be made from cactus leaves, pineapple fibers, apple skins, grape skins and other byproducts of the wine industry, and more. Leather fashion likely won’t be going anywhere. But, through biotechnology, there is a glimmer of hope that the fashion industry at large will pivot to materials that are far kinder to the planet, people, cows, and all of the wildlife affected by leather production.