Leather Alternatives: From Mangos to Mushrooms

The evolution of one of the oldest materials on Earth

Last week I published an article in SynBioBeta on the progress in the field of biomaterials. If you are curious to know what other industries synthetic biology is poised to disrupt, check it out!

Every time I travel to Colombia, I bring back a suitcase filled with two things: coffee and shoes.

You might be surprised—isn’t it Italy where you go to buy shoes? Sure, if you can afford it. While Italians do have superior design and construction, Colombia is known for its leather. There is a strong culinary tradition of eating beef and a big ranching culture. The abundance of cheap leather comes as a byproduct of animal farming. However, it’s more than just leftovers from a sacrificed cow: leather is a valuable product and an incredibly versatile material that fuels the creativity of Colombian artisans, craftsmen and companies that make beautiful products from it.

Leather is used for so many applications: You can make clothes, handbags and shoes out of it, furniture, harnesses, saddles and other things that can withstand a lot of wear and tear. Well-made leather goods serve the owner for many years without losing their quality and integrity; in fact, they acquire additional character over time by developing unique, organic (dis)coloration and patina.

But if you start thinking about it, using leather for clothing, furniture and everyday objects is kind of morbid: it is quite literally the skin of a dead animal we are wearing.

This is one of the main reasons why many people choose to not use leather. Luckily for them, vegan alternatives for leather products are widely available—and are, in fact, cheaper than the real thing. The development of polyurethane imitation leather in the mid-twentieth century helped industries keep up with the growing demand and bring down the price point of goods. Almost anyone could afford to buy a polyurethane leather couch. It looked just as stylish and did not get stained if you spilled something on it. But the quality of synthetic leather substitutes is not the same: they do not last as long nor age in the same beautiful way as does real leather.

That’s the conundrum of the textile and leather industry: natural leathers are great but getting them requires growing and killing a cow, tanning the hides, and working within the confines of the sizes and shapes those hides come in. Synthetic leathers, on the other hand, are cheap, they can be produced in the desired size and quantity, and are easily scaled to meet the demand, but they don’t have the same quality, durability and the feel of real leather. And they are made from oil. While the production of natural leather carries a significant environmental footprint, it is still a renewable AND biodegradable material. Polyurethane is not.

On the other hand, leather’s reputation is tarnished by the issues of animal cruelty, the carbon footprint of cow farms and environmental pollution. Leather tanning is a big part of the problem. Tanning is a process that improves the durability of leather. Natural hides are susceptible to decomposition under the influence of microbes and the elements. To prevent that, the hides are treated with special chemicals that improve the structure of the leather and prevent degradation. Historically, this was done using tannins from plants like oak, chestnut or hemlock. The complex preparation process took months and involved using things like horse urine, dung and animal brains to prepare leather for its final applications.

Today, more efficient tanning solutions are available. But that does not mean that the process is completely harmless: tanning generates byproducts like toxic formaldehyde, heavy metals such as chromium and arsenic and other chemicals that are harmful to people and can pollute our water supply. Besides, tanning reduces the biodegradable properties of leather. In a way, that’s the whole point; but given our fast-fashion culture where things are more disposable than ever before, leathers end up in landfills and their lifecycle is not much better than that of plastics.

Moo-ving away from animal leather

So, the question remains open: can we find a material with exceptional mechanical properties, without a heavy environmental footprint and that can be manufactured in large quantities? Let’s take a look at a few options.

Some companies are developing new technologies that make tanning a more sustainable process—and preserve the biodegradability of leather. Others are skipping the tanning step altogether. There are several designers, for example, who are making leather-like materials from kombucha scoby. The thick cellulose mats formed by the microbes and yeast that make the delightful effervescent drink have similar properties to those of leather when it’s dried. Other sustainable leather alternatives are made from pineapple leaves, apples and lemons, coconut shells, mangoes and even cacti. But the most successful leather-imitating materials so far have been mushrooms.

Mushrooms are part of the fungal kingdom, so their proteins are much more similar to animal proteins than plant ones. The tensile properties, look, feel and even smell of mushroom leather are said to be very similar to the real thing. Even more importantly, it can be grown into any thickness and size—and these materials are naturally water resistant, unlike leather which requires extensive chemical treatment to make it waterproof.

“Mushroom leather”, however, is a bit of a misnomer. The material is actually made not from the mushrooms themselves, but from mycelium, the sprawling root structure of fungal organisms. Mycelium looks like the white mold that grows on top of old strawberries in the fridge. This thick mycelium foam can be compressed and treated with enzymes to achieve a material that is exceptionally similar to animal leather. Its properties, like elasticity, texture and shine, can be adjusted by using genetic engineering, different processing steps or simply changing the growing conditions.

Mycelium leather has generated quite a bit of hype around it: it appeared at the New York Fashion Week in 2020 and products made from it were immediately sold out from stores. Companies like Mycoworks and Bolt Threads which are making mycelium materials have managed to sign up some big-name brands for developing their first products. For example, Bolt Threads created a consortium that included brands like Adidas, Kering, Lululemon, and Stella McCartney, and Mycoworks is collaborating with the luxury brand Hermès.

Part of the reason why it’s been so hard to lay your hands (quite literally) on the sample of mycelium leather is that making enough of it to meet the demand is currently difficult. It is a new technology, and like all new technologies, scaling it takes time. After struggling to raise additional funds for scaling, Bolt Threads announced that it will be pausing the production of its mycelium leather for the foreseeable future.

The price point also makes mushroom leather a bit out of reach. For example, the mango leather produced by a Dutch company Fruitleather costs around $22 per square foot and pineapple leather is less than $2 per foot. In comparison, the current price of mushroom leather lands at around $50 per square foot, and some types are even more expensive. No wonder only high-end brands like Hermès can afford to use it.

Unfortunately, sacrificing a cow to make a handbag might still be our best option today. But with all the momentum around scaling biomanufacturing, alternative leather products might begin to pop up like mushrooms before we know it.