Mycelium materials: between culture and product

A material "made of mycelium" is not a piece cut from an underground network in a forest. Most often it is created in controlled cultivation, in which a fungus grows through a shredded lignocellulosic substrate: straw, sawdust, husks or other agricultural residues. Hyphae branch between the particles and form a biological binder. Once the desired shape is reached, the element is dried or heated to stop growth and lower the moisture content.

The process resembles both fermentation and the forming of a composite. First a species or strain has to be chosen, a clean substrate prepared, moisture and density set. The material then goes into a mould, but it grows — its properties change over time. Temperature, access to oxygen and carbon dioxide concentration affect the density of the network. Even the shape of the container can change the direction and evenness of colonisation.

Research in Scientific Reports showed that production parameters affect mechanical properties. The type of substrate, particle size, the way it is pressed and the growth conditions all change density, stiffness and strength. "Mycelium composite" is therefore not one material with a fixed specification. It is a family of recipes, much like concrete, paper or wood-based board. The result has to be described with figures and a test method, not with a photograph of a white surface.

The easiest applications exploit low mass and the ability to fill a mould. Protective packaging can replace some foams in products that need not carry heavy loads or stay out in the rain for long. Acoustic and insulating panels benefit from porosity. Display or design elements can be produced in short runs. The closer one gets to a building structure or a car part, the more important standards, repeatability and long-term behaviour become.

Moisture is the fundamental limitation. A porous material readily exchanges water with its surroundings, which changes mass, dimension and mechanical properties. A coating may improve resistance but complicates compostability and the environmental balance. Drying has to lower biological activity and prevent unwanted growth during use. A product should not release spores or develop inside a wall merely because marketing calls it "living".

Fire resistance likewise requires a specific test. Some composites char and may compare favourably with certain plastics, but the recipe, thickness and finish change the outcome. The result for one sample must not be transferred to a whole category. In construction what counts is the classification of the finished assembly, the method of installation, smoke and behaviour after wetting — not a short video of a flame held to a corner.

The environmental promise begins with a waste substrate, a low growth temperature and the possibility of using local biomass streams. It does not, however, end with those three points. The substrate is often pasteurised or sterilised, the room requires climate control, and the finished element has to be dried. Transporting a light but bulky product may matter. A life-cycle analysis takes in energy, water, the proportion of failed batches, coatings, durability and the end-of-life scenario.

Comparison with plastic makes sense only for the same function. If a packaging insert protects a product equally well and enters an appropriate waste system, footprints can be compared. If it cracks more often, damages the device being shipped or requires an additional film, the balance changes. "Biodegradable" also needs conditions: a material may break down in industrial composting but not necessarily quickly in a dry household bin or in landfill.

A further question is the biological safety of production. A nutrient-rich substrate is attractive to many microorganisms. Contamination by mould can destroy a batch, change properties or introduce unwanted metabolites. Control therefore does not consist of avoiding "chemicals" but of hygiene, traceability of the strain, monitoring of parameters and criteria for rejection. Industrial scale requires procedures closer to food production or fermentation than to a ceramics studio.

A designer has an unusual aesthetic available. The surface may retain the trace of plant particles, a white bloom of hyphae or the texture of the mould. Variability can be attractive in a single object but difficult in a series. It has to be decided which differences are acceptable character and which are defects. Colour should not substitute for a test: a darker patch may be only substrate, but it may also signal moisture or contamination.

Leather-like materials are made by a different route from thick sawdust composites. They use mats of mycelium, which are cleaned, pressed, dyed and finished. The final product may contain additives improving flexibility and durability. The phrase "100 per cent fungus" therefore calls for a check of the composition. Resistance to bending, abrasion and water matters, as does the possibility of repairing and recycling a multi-layer material.

Standardisation is less spectacular than a prototype, but it determines the move to market. A producer needs a density range, dimensional tolerance, a compression test, behaviour in humidity, flammability and ageing. A customer has to know whether two batches will perform similarly. Laboratory testing should report the number of samples and the variability, not only the best result. Otherwise a biomaterial competes on a story rather than on a parameter.

The most honest assessment does not ask whether mycelium will "replace plastic". It asks which specific application suits its profile. A single-use protective insert, a light interior panel and a structural element have entirely different requirements. A composite may be good where low mass, forming without machining and a local substrate matter, and poor where a product works outdoors for years. Selectivity is not a failure of the technology; it is a condition of mature deployment.

A fungus brings a process to design, not a magical raw material. Hyphae build structure under mild conditions, but a human chooses the strain, the waste, the energy, the additives and the end of the product's life. Only a full record of those decisions allows anyone to say whether a material is genuinely better than what it is meant to replace. The most interesting thing about mycelium is therefore not the slogan "grown instead of manufactured", but the possibility of joining the biology of growth to measurable engineering practice.

Material properties begin in the growth medium

Haneef and colleagues grew Ganoderma lucidum and Pleurotus ostreatus for 20 days on two substrates: pure amorphous cellulose and cellulose mixed with potato-dextrose broth. Growth was then stopped by heating for two hours at 60°C. The medium altered both composition and mechanics: cellulose-grown films contained a greater chitin fraction, had a higher Young’s modulus and showed lower elongation at break. All samples had water-contact angles above 120°, indicating strongly hydrophobic surfaces. This is useful evidence that fungal-material properties can be tuned through biology and cultivation conditions. It is not proof of product readiness. The study did not test long-term ageing, fire performance, emissions, real-world composting or a full life-cycle balance. “Mycelium-based” therefore names a manufacturing platform, not an automatic guarantee of durability or environmental superiority over leather or plastic. Product claims need formulation-specific and application-specific tests.