Mushroom Eco-Leather: The Next Step for Sustainable Fashion?

While there is clear demand within the fashion industry and among consumers for vegan alternatives to leather, there are few sustainable options that can match current commercial needs. 

Mycelium- or fungi-based vegan leather alternatives have been proposed previously as a low-cost and environmentally friendly type of eco-leather, but were initially dismissed due to challenges in scaling up production.

Now, research published in Research Directions: Biotechnology Design suggests a new method for growing mycelium “leather mats” that is fast and could be easily scaled to be economically viable.

Finding alternatives to leather

Leather has been the epicenter of much debate within the sustainable fashion industry. Some argue that leather is merely a byproduct of the meat industry and that it is better to turn this into handbags or shoes than let it sit and rot in a landfill. On the other hand, the environmental impact of cattle rearing is stark, with leather production also requiring the use of harmful chemicals to properly process and dye the animal hides.

The most common vegan leather alternatives are made from petroleum-based polymers. This sidesteps the need for animal rearing and chemical treatments, but raises additional concern over how these leathers might contribute to the global plastic waste problem.

“The extensive treatment needed to transform hide into traditional leather comes with high environmental costs,” said lead study author Dr. Assia Crawford, an assistant professor in the College of Architecture and Planning at the University of Colorado Denver.

“Moreover, petrochemical alternatives like faux leather, which have become increasingly popular in response to the challenges of animal leather production and associated ethical concerns, also have significant environmental impacts associated with the extraction of fossil fuels, long degradation spans, and potential off-gassing risks. Developing better alternatives is crucial in today’s environmentally fragile world.”

This is where mycelium materials come in. Mycelium is the root-like fungus structure that grows beneath mushrooms to provide them with water and nutrients. Mycelium-based bio-composites have already shown promise in other applications, such as packaging, building materials and insulation.

“As our world searches for sustainable alternatives to traditional materials, there has been growing interest in using living organisms to produce biodegradable material substitutes with low environmental impact – such as mycelium leather, which is an eco-friendly leather alternative,” Crawford said.

From fungi to fashion

In the new study, researchers studied the potential of two fungal species for mycelium leather growing: Ganoderma lucidum (reishi), a medicinal mushroom commonly used in bio-design projects, and Pleurotus djamor (pink oyster), a gourmet mushroom that enters the fruiting stage very quickly.

These mushrooms were introduced to a special substrate paste created by the researchers to optimize growth and scalability. Using a paste rather than a solid or liquid substrate balances the need for high nutrient content with a smaller nutrient particle size, which aids in the uptake of nutrients. The fungi species were left to grow in aluminum trays for 21 days, before the resulting mats of mycelium fungal threads were harvested and analyzed.

"As researchers, we have a responsibility to continue developing better materials in response to the climate crisis, which is what the study aims to do,” said Crawford.

Using their special paste substrate, the researchers were able to grow thicker mycelium mats over a shorter period of time in comparison to those grown on nutrient-enriched agar or liquid culture. The mats grown from the paste substrate were also exceptionally easy to harvest – they had grown to be so strong that they could be peeled up in one piece.

The researchers also conducted basic tensile strength tests and experimented with a number of post-processing treatments designed to improve the tensile strength of the material and alter its appearance to match traditional leather. While the mycelium material was not able to match the tensile strength of other faux leather or animal leather products, the researchers believe that laminating multiple layers could reinforce the material sufficiently.

Aesthetically, the team found that final mycelium leather responded to heat and pressure treatments and could be embossed similarly to animal leather. It also readily accepted leather dye. 

“Bio-design methods like the ones explored in our study contribute to developing high-quality, scalable, biodegradable material alternatives. These in turn have the potential to address the environmental challenges of high textile consumption,” Crawford said.

“Indeed, the flexible nature of pure mycelial mats is a compelling potential substitute for non-woven materials such as animal-derived leather and petroleum-based faux leather alternatives.”

Reference: Crawford A, Ruthanna Miller S, Branco S, Fletcher J, Stefanov D. Growing mycelium leather: a paste substrate approach with post-treatments. Res Dir Biotechnol Des. 2024;2:e6. doi: 10.1017/btd.2024.6

This article is a rework of a press release issued by Cambridge University Press. Material has been edited for length and content.