Mycelium-Based Materials — How It's Made

Episode 14

A commercial mycelium material growth cycle runs between five and ten days from inoculation to harvest-ready composite. In that window, a living fungal network threads through agricultural waste, bonding the material as it grows, producing a composite shape without casting, pressing, or chemical binders. The binder is the organism. The process runs at room temperature. The energy input is a fraction of what conventional foam manufacturing requires.

This episode covers how that process actually works.

Grown, Not Manufactured

Mycelium-based materials are grown. The process is a managed biological growth cycle — a form of solid-state fermentation — in which a fungal culture colonizes an agricultural substrate and, in doing so, produces the structural composite that becomes the final material. There is no furnace. No melt. No chemical reaction chamber. The manufacturing step is biology.

The contrast with basalt fiber — covered in the previous episode — is almost total. Basalt: 1,400 degrees Celsius, continuous melt, platinum-rhodium bushings, mechanical drawing at 20 to 100 meters per second. Mycelium: 20 to 30 degrees Celsius, biological colonization, five to ten days, a living organism doing the binding work.

The Five Steps

Substrate preparation. Agricultural feedstock — corn stalks, wheat straw, hemp hurds, sawdust, cottonseed hulls — is processed to consistent particle size and then pasteurized or sterilized. Pasteurization heats the substrate to 65 to 85 degrees Celsius. Sterilization goes above 121 degrees Celsius under pressure. Both aim to reduce competing microorganisms so the fungal culture can colonize without being outcompeted. Sterilization is more thorough but more energy-intensive. Pasteurization is faster and cheaper but less complete. Different producers make different choices based on their contamination tolerance and operating economics.

Inoculation. The prepared substrate is mixed with fungal spawn — living mycelium culture grown on a grain or sawdust carrier, ready to be introduced into a new substrate. The inoculation ratio affects colonization speed and contamination risk. More spawn means faster colonization and lower contamination risk, but higher material cost per batch.

Colonization in molds. The inoculated substrate is packed into molds — trays, panels, or custom shapes matching the final product geometry — and moved to a controlled environment: 20 to 30 degrees Celsius, high humidity, managed carbon dioxide levels. The mycelium grows through the substrate over five to ten days. Fungal hyphae — individual threads of the network — extend through the material, physically binding the substrate particles together as they grow. No adhesive is applied. The binding is produced by the organism.

Heat treatment. When colonization reaches the target density, molds are removed, and the material is heat-treated at 60 to 80 degrees Celsius for several hours. This kills the living mycelium, stopping biological activity. Without this step, the material would continue growing, potentially produce mushroom fruiting bodies, and change its properties in storage. After heat treatment, the material is biologically inert.

Finishing. The material is dried, surface-treated, cut, or pressed depending on application. Some producers apply a thin outer mycelium skin grown under different conditions for a smoother surface finish. Packaging applications may go directly from heat treatment to assembly. Architectural or acoustic applications typically involve additional steps.

The Energy Reality

Total energy consumption per kilogram of finished mycelium material is estimated at roughly 1 to 5 megajoules, depending on process specifics. The highest-energy step is substrate sterilization or pasteurization. Colonization itself requires only enough energy to maintain ambient conditions — low, especially in climates near the target temperature and humidity range.

For comparison: producing one kilogram of expanded polystyrene — the foam packaging mycelium products most directly compete with — requires approximately 80 to 120 megajoules. The difference is not marginal. It is one of the most frequently cited structural advantages of mycelium materials, and the numbers support the claim.

The Batch Constraint

This process is inherently batch-based. Each mold is a discrete cycle. Five to ten days per batch, set by biology — not mechanics, not temperature, not chemistry. You cannot compress the colonization timeline beyond the organism’s biological capacity without degrading the material or increasing contamination risk.

This shapes production economics in ways that are structurally different from continuous manufacturing. A larger facility runs more simultaneous batches, but cycle time per batch doesn’t change. Throughput scales with facility footprint and mold capacity, not with process speed. This is a feature of the process that has to be designed around — not a problem waiting to be solved.

What’s Contested

Contamination management at scale. In small-batch conditions, contamination from competing molds and bacteria can be kept low through careful technique. At industrial scale — many simultaneous batches in a large facility — it becomes a significant operational challenge. Commercial producers describe their management systems but rarely disclose loss rates. How well contamination can be controlled at scale, and at what cost, is one of the genuine unknowns in the industry’s scaling story.

Colonization consistency. Mycelium composite properties depend on how thoroughly the mycelium has grown through the substrate. Eighty percent colonization produces different properties than ninety-five percent. Visual inspection may not distinguish between them. Non-destructive testing methods for colonization completeness are not well-developed. Quality assurance is an active challenge without a settled solution.

Moisture performance in service. Mycelium composites absorb moisture from humid environments, and moisture uptake reduces compressive strength. Producers address this with surface coatings, but long-term moisture performance in real service environments — beyond packaging, into building insulation or acoustic panels — is not fully characterized. Independent comparative testing is limited.

What’s Unknown

Whether the economics close for high-volume, lower-margin applications is not yet demonstrated. The cycle time constraint means facility investment per unit of annual output is higher than for continuous manufacturing. The process has been shown to work economically for premium and specialty markets. Whether it works for commodity volumes is an open question.

How fully the process can be automated — given that it involves managing a living organism rather than a mechanical reaction — is also unknown. Current commercial operations involve significant manual labor in inoculation and mold handling. Automation would change the economics substantially, but biological variability may set limits on how far automation can go.

The Real-World Signal

In 2023, Ecovative Design announced a strategic shift toward licensing its process technology rather than positioning itself primarily as a materials producer. The move frames the process knowledge itself — protocols, strain selection, contamination management, quality control — as the durable competitive asset, not the product.

If the process were easy to replicate independently, licensing it would give away the core value. The fact that Ecovative is licensing suggests the process knowledge is genuinely difficult to transfer without support, and that scaling through existing manufacturers’ facilities may be faster than building dedicated new ones. Whether licensees can implement the process consistently is being tested now.

Three Takeaways

Mycelium materials are grown, not manufactured in the conventional sense. The binder is the organism itself, produced at room temperature, without chemical adhesives. That is a genuinely different production model from anything else in advanced materials.

The batch nature of the process is a structural constraint, not an engineering problem. Five to ten days per cycle, determined by biology. Throughput scales with mold capacity and facility footprint, not with process speed. This shapes facility design and production economics in ways that differ from continuous manufacturing.

Contamination management, colonization consistency, and moisture performance are the three active operational challenges not yet fully solved at industrial scale. They are being managed. The cost and completeness of that management at scale is not yet transparent.

The Open Question

Mycelium materials have a compelling process story — low energy, waste inputs, room temperature, biological self-assembly. If that story holds at scale, why haven’t more manufacturers adopted the process? What is it about the biological nature of production that makes it harder to transfer and standardize than a conventional manufacturing process?

Next: Episode 15 — Recycled Rare Earth Alternatives | Topic 5: How It’s Made — The Basic Process