Series | Hard Reset

Inside the lab growing leather from mushrooms

Even Hermès is using this ‘shroom leather. Are biomaterials going mainstream?
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As the fashion industry faces pressure to become more sustainable, many companies are turning to one of the promising leather alternatives on the market: mushroom leather. 

It’s not just fringe fashion. In March 2021, the French luxury goods company ​​Hermès released a new version of its popular $5,000 Victoria duffle bag that’s made from mycelium — the thread-like fungal roots that grow underneath mushrooms. The fungus leather shares common traits with animal leather: durability, strength, aesthetics, and feel. But the differences in environmental impact are stark. 

The majority of leather products come from cattle, which are one of the world’s top greenhouse gas emitters, mainly through belching methane. And while most cattle are raised and slaughtered for beef and dairy products, leather helps sustain the industry, and the leather tanning process can release toxic chrome into the water supply. 

As a cattle byproduct or coproduct, the supply of leather doesn’t necessarily follow demand — an economic effect that’s led fashion companies to incorporate more plastics into leathers, which also damages the environment. 

“[Leather is] a supply chain that doesn’t scale.”

Matthew L. Scullin, CEO of MycoWorks

“The fashion industry can’t just say, “Hey, I’m going to turn up a knob this year, we need more leather so I’m going to find more leather.”

Founded in 2013, MycoWorks is a California-based company that uses mycelium to produce sustainable materials. The startup is one in a growing field that believes the best way to curb the fashion industry’s environmental footprint is through fungi — a vast kingdom of diverse and largely mysterious organisms that account for 25% of all biomass worldwide.

The mysterious world of fungi 

The fungus kingdom is estimated to comprise more than 3.5 million species, of which the vast majority remain undiscovered. When most people imagine fungi, they picture a mushroom, like grocery-store white mushrooms, portabella caps, or the red and white Amanita muscaria variety found in Super Mario. 

Mushrooms are the fleshy, fruiting body of a fungus. People use the non-toxic varieties not only as a nutrient-rich food source, but also as psychedelics, medicine, and a natural form of pest control. In the fungus kingdom, however, the mushrooms we see above ground are just the tip of the iceberg.

Often called “the hidden kingdom,” the bulk of fungal activity occurs underground or out of sight. The main role of fungi is decomposition. And it was an incomplete understanding of that role that caused taxonomists to label fungi as plants for centuries. It wasn’t until 1969 that the ecologist Robert Whittaker proposed separating them from plants and animals into their own kingdom. 

The main difference between fungi and the other two kingdoms centers on food. Plants produce their own food through photosynthesis, while animals eat and digest food in the environment. Fungi take a unique approach: Mycelium spreads from mushrooms and secretes enzymes onto a food source, such as a fallen tree branch or an animal carcass. These enzymes break down the matter so that the mycelium can absorb it as energy. By decomposing nature for billions of years, fungi and their vast networks of mycelium have helped maintain an ecological equilibrium that’s enabled the other two kingdoms to thrive. 

It turns out that the way mycelium networks naturally grow and expand can be exploited to create sustainable materials, from a mushroom leather jacket to structures far more complex. 

Using mycelium in fabric production 

Mushroom leather has been used as a leather alternative for nearly a decade. The process involves growing mycelium, which naturally forms a solid foam that can be compressed into a material that resembles leather. But this technique limits producers’ ability to customize for specific traits, which makes most mycelium leather inferior to animal leather. 

MycoWorks has developed a new technique called Fine Mycelium, which “engineers mycelium during growth to create the proprietary, interlocking cellular structures” that enable the company to customize the biomaterial for traits like flexibility, softness, durability,  and strength. To produce the biomaterial, the company adds mycelium to an agricultural byproduct like sawdust. 

The mycelium then feeds on the material and grows in trays, which, unlike cattle, can be any size, meaning MycoWorks could produce large swaths of the biomaterial — called Reishi, after the mushroom — without any breaks or seams. 

Since 2013, MycoWorks has scaled up and fine-tuned its production process by incorporating testing machinery that provides precise measurements on the softness and durability of each batch of material. 

“We’ve been able to push this process forward in a way that’s more like a biotech, or a more traditional manufacturing process, that’s tightly controlled,” Scullin told Freethink. “We have some trays that are running material for say, handbags, other materials that are being built for shoes. So within a plant we can very easily customize what’s going on in each tray based on the orders we receive from our customers.”

Each piece of mushroom leather has its own feel and look, in addition to the patina that develops over time.

(Reishi also develops a patina.) But beyond the clear applications in the fashion world, developing sustainable alternatives like Fine Mycelium isn’t simply about replacing leather and plastics.

Shifting how we think about biomaterials 

Before MycoWorks was developing leather alternatives, co-founder Philip Ross spent years using mushrooms to create other things, including simple bricks, art objects exhibited around the world, and furniture like chairs, tables, and footstools. The projects highlighted the untapped potential of mycelium-based biomaterials. 

“Phil’s work, I would say, is foundational to our current understanding of what mycelium can do, and we’re really just scratching the surface,” Sophia Wang, co-founder of MycoWorks, told Freethink.

What that future looks like is hard to say. Beyond the fashion industry, customizable biomaterials like Reishi could be used to build all sorts of products and structures, including houses. For example, the U.S.-based architecture firm redhouse studio is already working on building mycelium-based housing in Africa, and has even collaborated with NASA on designing fungal-based systems that could convert waste into structures on other planets. 

As industries continue to face the social and economic consequences of climate change, it may only be a matter of time before sustainable biomaterials become mainstream. 

“I don’t think leather is going away, and I don’t think plastic is going away,” Scullin told Freethink. “I think that, eventually, those materials are going to run into even bigger constraints, even bigger walls, than they are today. Material like Fine Mycelium is going to be able to pick up that slack.”

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