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No Cap: Mycelium Study Stirs Industry Debate

Its no secret that the fashion industry is facing increasing pressure to reduce its environmental footprint, respond to consumer demand, comply with evolving environmental regulations and meet shareholder targets.

This pressure has manifested with the exploding demand for both non-animal and non-plastic materials, with a proliferation of alternative leather options hitting the market, utilizing materials from grapes to cactus and other bio-based goods. These alternatives are expected to comprise a $2.2 billion annual market as early as 2026, according to the Material Innovation Initiative’s 2021 State of the Industry report.

While many of these alternative leather technologies promise advantages over incumbent leathers concerning their carbon footprint, many still contain enough plastic—plastic textiles, including many “vegan” leathers, comprise 36 percent of all global plastic waste, according to Bain & Company research—to prevent efficient biodegradation and might not offer any significant advantage over either animal or plastic-based leathers.

And while these vegan leathers were a step in the right direction, they’re more of a red herring that distracts from problems ranging from microplastic pollution to landfill and ocean accumulation. These issues have such severe negative impacts that the United Nations recently resolved to end plastic pollution. It’s apparent that a holistic solution—one that avoids the carbon emissions and cruelty of animal hides while also avoiding plastic—is the ideal solution.

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This is where materials made from mycelium come into play.

Mycelium-based alternative leathers could be the rare development option that fits the dual criteria of low-carbon and near-zero plastic use.

The industry has taken notice.

The first peer-reviewed “Life Cycle Assessment (LCA) for Reishi”—a new class of luxury material made from mycelium and developed by biotechnology company, MycoWorks—has been published in the Environmental Sciences Europe journal and peer-reviewed by sustainability professionals Ellie Williams, Katarzyna Cenian and Laura Golsteijn from environmental consultant PRé Sustainability. To date, MycoWorks’ materials have been used by brands and companies including Hermès, Heron Preston and General Motors.

“The Life Cycle Assessment of MycoWorks Reishi: the First Low-Carbon and Biodegradable Alternative Leather” report, which MycoWorks funded, details its cradle-to-gate carbon footprint and a broader environmental profile.

What to know

Not all mycelium materials that come to the market are plastic-free. Of the 11 companies studied, only three were allegedly truly plant-based: MycoWorks, Mogu and Ecovative. The carbon intensity of production for each of these has not yet been published. The report found that the production techniques differ where Ecovative’s Forager material uses an active growth process while Mogu and MycoWork’s Reishi use a passive growth methodology.

The active growth process involves pumping large amounts of carbon dioxide into the growth chamber because a high CO2 environment promotes mycelium growth while preventing mushrooms from sprouting. The carbon footprint is likely high for Ecovative due to the combustion of fuels and the CO2 production source and, in turn, the release of this CO2 into the atmosphere during the mycelium growing process. MycoWorks and Mogu, however, consume no gas during their passive growth process.

Bolt Threads, Modern Meadow, Vegea and Desserto were among the brands that use plastic to create a material whose performance is on par with animal leather. Based on the publicly available information regarding the Ecovative process used to produce its Forager material and the mycelium for Bolt Threads’ Mylo option, the CO2 consumption is so high that it potentially exceeds that of animal leathers by an order of magnitude, according to the report. That said, the only two potential candidates that exist as both low-carbon and biodegradable materials with a natural haptic would be mycelium materials from MycoWorks and Mogu. While the carbon footprint of Mogu has yet to be published, MycoWork’s Reishi carbon footprint is detailed within the report.

Again, the report was commissioned by MycoWorks, and Ecovative, for one, takes issue with how the report characterizes its production process.

“The claim is spurious and based on data that is not applicable to the growth process of Forager mycelium materials or Ecovative’s AirMycelium technology,” a spokesperson for Ecovative said. “Ecovative is completing a comprehensive LCA on Forager hides and foams in the next 12 months, our team is very happy with our initial internal analysis of our production process…and the planet-positive benefits they can bring to the fashion industry.”

Modern Meadow also disputed the report’s findings, stating that it does not use a plastic-based material. Bolt Threads attacked inaccuracies around its alleged carbon consumption as “patently false.”

“While we celebrate and value progress across the category of alternative leathers and don’t want to discourage any innovation on a similar mission, we must emphatically state that the carbon dioxide (CO2) calculation reported by MycoWorks is patently false, and has never represented the production of Mylo,” Libby Sommer, director of corporate responsibility at Bolt Threads, said. “The amount of carbon dioxide that MycoWorks attributes to our production process would inhibit the growth of mycelium and may even kill our organism.”

“Further, based on measured data over several years, the COadded in our mycelium growing process is four orders of magnitude smaller than MycoWorks’ calculation. As a fellow company working in mycelium materials, we were surprised and dismayed to see MycoWorks making misleading claims such as this one,” Sommers continued. “As part of our commitment to building materials and production systems that prioritize the health of people as well as the planet, we have invested in numerous impact assessments to guide our scale-up in addition to employing a number of sustainability strategies to reduce our impact.”

Mogu confirmed that it uses a passive growth process. Desserto said it does not use mycelium in any of its materials. Vegea did not reply to Sourcing Journal’s request for comment.

Reishi is a relatively new biomaterial produced by McyoWorks Inc. as an alternative to traditional animal leather. It’s created with Fine Mycelium, a biotechnology platform invented by MycoWorks to engineer mycelium (the thin fibrous network that makes up the fungal organism) into custom-grown, made-to-order materials. Fine Mycelium also refers to the material created by this proprietary process, which undergoes dyeing, lubricating and finishing processes to be made into the leather-like product Reishi.

While the structural composition of Reishi as non-crosslinked, pure biomass means it’s biodegradable, it’s not yet clear if it meets the low-carbon criteria, as that information is not published. So, a Life Cycle Assessment (LCA) was performed to determine whether it meets the dual criteria essential for low-impact alternative leathers with the primary aim of challenging the apparent advantages of Reishi and comparing how it performs in different production-scale scenarios.

What was done 

An LCA compiles the inputs and outputs of a product system and evaluates its potential environmental impact. It can be used to quantify a product’s effect on several categories, such as water scarcity, ecotoxicity, land use, eutrophication and climate change. Accordingly, quantifying the carbon footprint of a product—i.e., the impact on climate change—is seen as an entry point for accessing ecological performance. Current LCAs don’t account for potential risks and impacts from micro and nano-plastic emissions in the environment.

Courtesy of Environmental Sciences Europe

MycoWorks produces Reishi tailored with an in situ embedded fabric material or without fabric. There’s a range of fabric materials that can be chosen to embed. The fabric material—the “structural base addition”—is placed into a tray and the mycelium grows to fill the fabric and then above it, thereby embedding it with the mycelium. As an additional option, the mycelium can grow to adequate strength and robustness with no added textile as the structural base addition. For the research published in Environmental Sciences Europe, three material variations were modeled: mycelium with cotton (100 percent cotton material embedded in mycelium), mycelium with recycled polyester (100 percent recycled non-woven polyester embedded in mycelium), and mycelium only (no fabric material embedded within the mycelium as a structural base, using solely mycelium).

For each of these model variations, the only differentiating aspect is the material for the embedded fabric.

What was found

Courtesy of Environmental Sciences Europe

The carbon footprint of 1 m2 of post-processed, finished, and packaged Reishi in the “pilot-scale day one” scenario was 17.65 kg CO2 eq. using cotton as the fabric material choice, 14.9 kg CO2 eq. using recycled polyester and 14.5 kg CO2 eq. using mycelium only. After implementing technical changes and process optimization, the footprint was reduced to its current state at the pilot scale of 9.34 kg CO2 eq. using cotton as the fabric material choice, 6.59 kg CO2 eq. using recycled polyester and 6.20 kg CO2 eq. using mycelium only.

For each scenario, the overall carbon footprint results are presented for Reishi produced with the three fabric options: mycelium with cotton, mycelium with recycled polyester and mycelium only. This is followed by the main findings from the contribution analysis for Reishi produced with mycelium only, which shows the relative contribution of different stages of production and post-processing to the total product carbon footprint. It’s important to note that it’s already been established that Reishi qualifies for the qualitative aspects of the functional unit—a material with natural haptics and satisfying the same performance, quality and hand feel as animal leather.

It was found that Reishi’s carbon footprint is as low as 2.76 kg CO2-eq per m2, or 8 percent, of the value of the bovine leather benchmark modeled. Furthermore, it was found that Reishi has a lower impact compared to bovine leather modeled across several impact categories, including eutrophication, ecotoxicity, human health effects and others. Reishi’s impact “hotspots” were determined, with the largest opportunity for further reduction being improved energy efficiency in the growth of mycelium, particularly the sterilization of raw material inputs via autoclave tools. It also shows that MycoWorks’ passive process for growing mycelium has a carbon footprint two orders of magnitude lower than incumbent mycelium growth processes that actively consume carbon dioxide gas, which MycoWorks’ process doesn’t require.

MycoWorks produces Reishi tailored to include or not include an embedded fabric material specified by the customer. The impacts of different fabrics vary considerably; for example, virgin cotton, virgin polyester and recycled polyester have a carbon footprint of 11.29, 5.59 and 1.11 kgCO2 eq./kg of textile, respectively, indicating that the fabric choice plays a significant role in the resulting total carbon footprint of Reishi.

The results have shown that Reishi holds promise as a low-impact leather-like material with natural haptics.

Studies have begun to hypothesize the environmental impact of fungi-based leather-like materials; however, the research presented in this paper is the first to use LCA to quantify the ecological effects of Reishi using primary production data. While the comparison to a specific natural material was out of scope of this research, to place the environmental footprint of Reishi in the context of other natural materials—i.e., natural haptics—in the market, the paper modeled a benchmark bovine leather.

Compared to the benchmark bovine leather modeled, Reishi has a significantly lower carbon footprint. The carbon footprint of the benchmark leather is 32.98 kg CO2 eq. per m2, which is considerably higher than the carbon footprint of Reishi, which (with mycelium only) is currently 6.20 kg CO2 eq. per m2 (an 81 percent reduction). These reductions compared to traditional leather are within a similar range to those claimed by plastic-haptic leather alternative products. However, it’s impossible to make any direct reduction comparisons due to myriad methodological differences. Modern Meadow estimates a 79 percent reduction for Bioleather1, Natural Fiber Welding estimates a 93 percent reduction for Mirium, Adriano di Marti estimates a 94 percent reduction for Desserto and a 94 percent reduction is estimated for Vegea.

Comparing the total environmental footprint of Reishi to benchmark bovine leather suggests the lower carbon footprint of Reishi comes without ecological tradeoffs. The total environmental footprint of the benchmark leather infers that the impact from “cancer human health effects” is the largest compared to the other impact categories. While the “resource use” impact categories appeared as most relevant for Reishi. This indicates that there would be no obvious burden shifting if Reishi was chosen as an alternative to the benchmark leather.

What’s next 

Mycelium is a technology that’s been developing for several years and has been undergoing industrialization and scale-up for a brief duration of that time. There have only been several thousand square meters produced. This study intended to show this material’s beneficial sustainability profile when produced at merely several hundred thousand square meters per year, including a carbon footprint of 2.76 kg CO2 eq/m2 (a 94 percent reduction compared to bovine leather), much lower impact on eutrophication, ecotoxicity and human health.

Given the urgency around taking action to reduce the impact of climate change from industries that use large amounts of carbon-intensive or polluting materials, like animal and plastic leathers, and the evolving climate policies to adhere to, it’s increasingly essential for users of these materials to have access to high-quality, sustainable options. This research provides a basis on which brands can access the carbon footprint of Reishi as a material choice. “Reishi is not just a leather alternative—it’s a new class of material.” Bill Morris, MycoWorks vice president of product, said.

But not everyone is convinced these findings are valid.

“It is surprising that this study published in Environmental Sciences Europe passed peer review through the journal. Several aspects of this study do not hold up to the principles of scientific integrity and rigor, including the use of subjective analysis (e.g., haptics or handfeel) and the estimates and assumptions used in the comparative analysis with other companies’ products,” Nicole Rawling, CEO of Material Innovation Institue, an independent think tank, said. “The issues around the study are so challenging that we would not be surprised if the journal removes the article from their site until a new analysis is conducted which complies with these scientific principles.”