Leather has been the mainstay of horse gear for centuries, providing the perfect combination of strength, flexibility and durability.
Researchers, who have reviewed evidence relating to the manufacture of leather-like material using fungi, believe it has considerable potential to be the best leather substitute in terms of sustainability and cost when compared to animal and plastic-derived versions.
Traditional leather and its alternatives are typically obtained from animals and synthetic polymers.
Leather can be considered a co-product of meat production, with both livestock farming and the leather production process increasingly considered to be ethically questionable and environmentally unfriendly over issues such as greenhouse gas emissions and the use of hazardous substances in the tanning process.
The production of synthetic leather materials from plastics such as polyvinyl chloride (PVC) or polyurethane (PU) also depend on chemicals derived from fossil fuels.
In their review, scientists with the University of Vienna, Imperial College London, and RMIT University in Australia describe fungi-derived leather substitutes as an emerging class of ethically and environmentally responsible fabrics, winning favour as an alternative to bovine and synthetic leathers.
While traditional leather and its alternatives are sourced from animals and synthetic polymers, these renewable sustainable leather substitutes are obtained through the upcycling of low-cost agricultural and forestry by-products into chitinous polymers and other polysaccharides using a natural and carbon-neutral biological fungal growth process.
Following physical and chemical treatment, these sheets of fungal biomass visually resemble leather and exhibit comparable material and tactile properties, they say.
The review team, led by material chemists Alexander Bismarck and Mitchell Jones from the University of Vienna, reported on the potential of fungus-derived leather in their paper in the journal Nature Sustainability.
Bismarck, who also holds a visiting professorship at Imperial College London, says fungus-derived leather is CO2 neutral as well as biodegradable at the end of its life span.
The imitation leather is produced by using agricultural and forestry by-products, such as sawdust, as feedstock for the growth of fungal mycelium, which constitutes a mass of elongated tubular structures. They are the vegetative growth of filamentous fungi.
Within a couple of weeks, the fungal biomass can be harvested and physically and chemically treated.
These sheets of fungal biomass look like leather and exhibit similar properties, Bismarck says.
The first biotech companies are already marketing materials derived from fungi.
Leather substitute materials derived from fungi typically contain completely biodegradable chitin (which acts as a stabiliser in the material) and other polysaccharides such as glucans.
Bismarck said: “We tend to think of synthetic leather, sometimes known as ‘vegan leather’, as being better for the environment. However, traditional leather might be ethically questionable, and both leather and plastic substitutes have issues with environmental sustainability.
“Fungi-derived leather brings none of these issues to the table, and therefore has considerable potential to be one of the best leather substitutes in terms of sustainability and cost.”
In their own studies, Bismarck and Jones (now affiliated with Vienna University of Technology) conducted research using fungal species, such as the white button mushroom A. bisporus and bracket fungus D. confragosa, to produce paper and foam-like construction materials for applications such as insulation.
In their review, the scientists examined the sustainability of bovine and synthetic leathers and present an overview of the first developments and commercialisation of leather substitutes derived from fungi.
According to the authors, one of the greatest challenges in the production of fungi-derived leather-like materials is still to achieve homogeneous and consistent mycelium mats that exhibit uniform growth and consistent thickness, colour and mechanical properties.
To date, the production of these materials has been driven mainly by entrepreneurial spirit.
They say fungi-based leather substitutes are of particular interest to sustainability-conscious consumers and companies, as well as to the vegan community.
“Substantial advances in this technology and the growing number of companies that are producing fungi-biomass-based leather alternatives suggests that this new material will play a considerable role in the future of ethically and environmentally responsible fabrics,” they write.
Jones, M., Gandia, A., John, S. et al. Leather-like material biofabrication using fungi. Nat Sustain (2020). https://doi.org/10.1038/s41893-020-00606-1