Mycelium biocomposites are among the most recent and conceptually radical entrants into the sustainable building materials field. The idea of growing building components from fungi rather than extracting or synthesising them represents a fundamental shift from industrial manufacturing toward biological fabrication. In the span of under two decades, mycelium materials have moved from academic curiosity to commercial products available for acoustic treatment, insulation, packaging, and experimental structural applications.
What Mycelium Is
Mycelium is the vegetative body of a fungus, consisting of a network of thread-like cells called hyphae. In nature, mycelium grows through soil, wood, and leaf litter, secreting enzymes that break down organic matter and absorbing the resulting nutrients. The visible mushrooms we recognise are merely the fruiting bodies of a much larger, largely invisible mycelial network that can span acres and live for centuries.
When mycelium is grown on a substrate of agricultural waste, the hyphae penetrate and bind the substrate particles together, forming a dense, coherent foam-like composite. After the mycelium has fully colonised the substrate, the material is heat-treated to kill the fungus, halting further growth. The result is a solid, lightweight, and fully biodegradable material composed of fungal biomass interlocked with the lignocellulosic substrate.
Substrates and Growth Process
The growth medium, or substrate, provides both nutrition for the fungus and the structural filler of the final composite. Agricultural wastes are used because they are abundant, inexpensive, and carry a low environmental burden from their prior purpose. Common substrates include hemp hurds, the woody core of the hemp stalk remaining after fibre extraction; corn stalks and cobs; rice hulls; cotton gin waste; and hardwood sawdust.
The substrate is first sterilised to eliminate competing microorganisms, then inoculated with mycelium spawn and packed into moulds of the desired final shape. Over 5 to 7 days in a controlled environment with appropriate temperature and humidity, the mycelium grows through the substrate, binding it into a solid mass. After full colonisation, the material is removed from the mould and dried in an oven or kiln at approximately 80 to 100 degrees Celsius. The heat both halts biological activity and removes water, bringing the moisture content below 10% for dimensional stability.
Physical and Mechanical Properties
Mycelium biocomposites are lightweight. Density ranges from approximately 50 to 200 kilograms per cubic metre depending on the substrate, fungal species, and degree of compaction. For comparison, expanded polystyrene foam has a density of about 15 to 30 kg/m3, and softwood lumber about 400 to 600 kg/m3.
Compressive strength is modest, typically 30 to 80 pounds per square inch, or 0.2 to 0.6 MPa. This is adequate for non-load-bearing applications such as insulation panels, acoustic tiles, and packaging, but well below the strength required for structural wall or floor components. Research into densification, fibre reinforcement, and cross-linking treatments to improve mechanical properties is active in several laboratories.
The thermal resistance of mycelium composites is approximately R-3 to R-4 per inch, or a thermal conductivity of 0.04 to 0.05 W/mK. This is competitive with mineral wool and cellulose insulation and better than some expanded polystyrene products. The material is also an effective acoustic absorber, particularly at mid and high frequencies, due to its porous, open-cell structure.
Fire Performance
Mycelium materials exhibit relatively good fire performance for a wholly organic material. Testing has demonstrated fire ratings of B1 or C under European EN 13501-1 classification, indicating limited combustibility. When exposed to flame, the material chars on the surface and the char layer insulates the underlying material, similar to the behaviour of dense timber. The charring releases water vapour from the cellulosic substrate, which helps to slow combustion. However, mycelium materials are not fireproof, and their use in building applications may require additional treatment or integration with non-combustible facings in assemblies requiring higher fire ratings.
Ecovative Design: The Pioneer
Ecovative Design, founded in 2007 by Eben Bayer and Gavin McIntyre in Green Island, New York, is the pioneering company in mycelium materials. The company's original product was a mycelium-based protective packaging sold under the MycoComposite brand, used by companies including Dell and IKEA as a compostable alternative to expanded polystyrene and polyethylene foam.
Ecovative has since expanded into building products with its MycoBoard technology, which uses mycelium to bind agricultural residues into panel products similar to particleboard but free of formaldehyde and other synthetic binders. The company also offers MycoFlex, a pure mycelium foam for textile and apparel applications. Ecovative's technology platform has been licensed to partners in Europe and Asia for local production.
MOGU: Design-Led Mycelium Products
MOGU, an Italian company based near Milan, has brought a design sensibility to mycelium materials. MOGU's acoustic panels and flooring tiles combine a mycelium core with a bio-based resin and natural fibre facing, creating products that are visually refined enough for high-end interiors while retaining the environmental benefits of biological origin.
MOGU Acoustic tiles use the natural sound-absorbing properties of mycelium composites, achieving Noise Reduction Coefficient values of 0.40 to 0.70 depending on thickness and surface treatment. The tiles are installed as suspended ceiling panels or wall-mounted absorbers in offices, restaurants, and public spaces. MOGU Flooring tiles offer a resilient surface suitable for moderate traffic areas.
Compostable End of Life
Both Ecovative and MOGU products are certified compostable at end of life under appropriate conditions. The mycelium component will biodegrade to carbon dioxide, water, and biomass within months in an active composting environment. This end-of-life pathway is markedly different from petroleum-based foams and composites, which persist in the environment for centuries if landfilled or littered.
Limitations and Future Directions
Mycelium biocomposites face several practical limitations that constrain current applications. The compressive strength is too low for structural use, and the material is susceptible to moisture absorption, which can lead to softening and fungal regrowth if wet conditions persist. Production speed is slow by industrial standards; a 5 to 7 day growth cycle is orders of magnitude longer than the seconds required to injection-mould a plastic part.
Ongoing research addresses these limitations. Genetic selection and engineering of fungal strains with faster growth and higher enzyme production is underway. Post-processing treatments, including cross-linking with natural oils and impregnation with bio-based resins, can improve strength and water resistance. Hybrid composites combining mycelium with structural fibres such as flax, jute, or bamboo show promise for load-bearing applications. The field is moving from proof-of-concept toward mainstream building products, driven by tightening carbon regulations and growing demand for materials that can be returned safely to the biosphere at the end of their useful life.