Spore-Tacular Future Materials: Innovations and Applications of Mycelium-Based Composites

1. Introduction

Over the previous decade, the construction sector has faced considerable challenges. Producing traditional construction materials consumes large amounts of energy and natural resources while polluting air, land, and water [2,3]. The demand for essential building materials like cement, bricks and timber has surged with the growing global population, making the supply difficult to maintain [2]. Traditional bricks, made from natural materials like silica, alumina, lime, iron oxide, and magnesium, are widely used, leading to resource depletion and sustainability concerns, posing significant challenges for future generations [4,5]. As global populations grow, yearly agricultural consumption rises, increasing byproducts like rice husks, cotton stalks, as well as straw. The majority of these secondary products are treated as residual and often discarded or incinerated, releasing CO2, particulate matter, and other greenhouse gases into the atmosphere [6,7]. Although some byproducts are used in fertilisers, livestock bedding, and low-quality building materials like bricks, green concrete, insulators, non-load bearing particleboards, also as fill material in road construction [7], much of their potential remains untapped.

The environmental risks of engineered materials made from depletable sources, like petroleum and natural gas, have driven interest in sustainable, biodegradable alternatives for various technological applications, particularly in the construction sector. Biocomposites, particularly those made from mycelium, are now being explored as suitable building and construction materials [8,9,10]. Mycelium based biocomposites (MBC) have been attracting attention in academic and commercial circles because their key component, mycelium, the actively growing structure of fungi responsible for nutrient absorption and colonisation, grow using minimal energy, produce no waste, and have diverse applications [11,12]. Mycelium form an interconnected system of delicate, filamentous structures called hyphae, each just 1-30 micrometres wide, starting from a single spore or hyphal fragment, which bind organic matter like plant and animal waste [13]. Mycelial filaments exhibit a multilayered architecture with unique chemical compositions, including proteins, glucans, and chitin [14]. Mycelium naturally binds organic matter through a network of hyphae, using nutrients from the substrate to grow. In nature, this organic matter comes from remains and waste products of plants and animals [15]. Waste streams including cellulose, tannin, cutin, and lignin, plus proteins, fats, also carbohydrates [16], can also be transformed by mycelium into valuable materials, converting agro-industrial residues with low or negligible market value into useful substances [17].

Natural materials like straw, sawdust, woodchips, cotton, and rice husk are commonly used as natural bases for creating nanocellulose as well as MBC [18,19,20]. As fungi grow on these substrates, their hyphae weave through cellulose, hemicellulose, and lignin-rich materials, up-taking nutrients and integrating bonds to form MBC [21]. MBC offer benefits in comparison to conventional synthetic materials: they are cost-effective, lightweight, and energy efficient, biodegradable, and have a low carbon footprint [14,22]. MBC also outperform synthetic materials like MDF, polyurethane and polystyrene in recycling efficiency, supporting a circular economy with reduced emissions and improved land use [23].

MBC are being explored for broad applicability, such as packaging [24], industrial tools [25], furniture [26], paper [27], building materials, textile films [28], insulation [8,29], as well as sound-absorbing and flooring composites [30]. In the building and construction industry, sustainable material development is gaining momentum for advancement of low-cost, environmentally friendly materials that reduce dependence on fossil fuels and promote sustainable practices [31]. However, since construction is sensitive to variations in product quality, new materials like MBC must undergo comprehensive structural integrity evaluations. The properties of MBC are influenced by variables including substrate composition, fungal strain, growth conditions, and processing approaches [13,18]. Understanding these factors can improve production, allowing MBC to be tailored for specific uses in the construction sector. Numerous reviews already exist on the advancement and application of mineral-based composites [18,30,32,33,34].

With controlled processing methods like hot pressing and precise growth environments, MBC can offer features such as fire resistance, as well as thermoacoustic insulation [11,27]. Mycelium is also being used in bio-integrated architecture, including building envelopes, where its flexibility and fire resistance make it an excellent insulating material. Studies show that building envelopes composed of mycelium sheets have thermal conductivity of 0.1 W/m.K, comparable to autoclaved aerated concrete [35], enhancing their viability as construction materials.

The material driven design (MDD) focuses on understanding the unique technical properties of mycelium to optimise its applications [36]. Successful mycelium cultivation requires specific ambient parameters, such as controlled light, temperature, and humidity to prevent contamination [35]. Recent research by Santosh et al. has investigated the compressive strength of MBC [37]. While it was shown that unadulterated mycelium blocks are suitable for use as non-structural walls owing to their lower compressive strength [37], Ghazvinian et al. (2019) investigated the compressive strength of MBC made from sawdust and straw as substrates, finding they lacked the needed for load-bearing structures [38]. However, Blauwhoff reported that densification through heat and pressure can improve the mycelium blocks’ strength by releasing trapped air, making it more viable for structural use [39].

2. Materials

2.1. Fungal Species

Various fungal inoculants influence the mechanical characteristics of the final MBC [40,41]. Unlike plants, which primarily rely on cellulose for structural support, fungi utilise chitin and chitosan, sustainable biopolymers. Chitin, also found in most insect and arthropod exoskeletons, is a polysaccharide with a linear structure, consisting of N-acetylglucosamine monomers [42]. Fungal mycelium, composed of dense and intricate hyphal filament networks, contain glucans, manno-proteins, chitosan, chitin, polyglucuronic acid, and small amounts of proteins and glycoproteins [43,44]. These constituents endow mycelium with structural and mechanical characteristics comparable to lignocellulosic materials like wood and cork [45].

Each fungal species uniquely affects factors like yield, mycelial filament thickness, morphology, and surface texture [18,27,46]. Hyphal structures are categorised as, skeletal, and binding types [47]. Wood-rotting fungi have gained scientific interest for their role in wood decomposition and biotechnological applications [47]. Pleurotus species, particularly Pleurotus ostreatus and Pleurotus pulmonarius, are commercially valuable and widely cultivated due to their nutritional and medicinal benefits [48]. Additionally, various species within the Pleurotus genus are recognised for their medicinal value, providing bioactive compounds such as polysaccharides, peptides and proteins [46,49].

Sydor et al. (2022) [16] noted that most MBC research focuses on white rot fungi, with Ganoderma lucidum and Pleurotus ostreatus frequently cited for MBC production from 2012 to 2022 (n>40 publications). Trametes versicolor was also frequently utilised and cited, appearing in 10 publications from 2012-2022. All these fungi are known to cause white rot [16]. According to Sharma et al. (2024) [50] Ganoderma species are favoured in MBC due to their rapid growth and ability to thrive on organic waste substrates. Notably, Ganoderma lucidum exhibits high elasticity, making it particularly suitable for packaging and construction materials [50]. Furthermore, these species can produce a tightly woven mycelial mat [16]. However, Ganoderma spp. also present certain drawbacks, such as high moisture absorption tendency, limited tensile resistance, vulnerability to biological degradation, and the necessity to inactivate the fungal species [27].

The mycelial network develops from a spore, propagating through cell wall growth at the hyphal tips. Hyphae consist of compartments separated by septa, which Facilitate the efficient transport of nutrients, water, and micro-molecules. This structure provides both protection and mechanical strength to the mycelium [40,51,52].

Mycelial networks can be classified into monomitic, dimitic, and trimitic systems, each defined by their hyphal structures: generative, binding, and skeletal hyphae [27,53]. White rot fungi include both monomitic and trimitic species, known for their ability to produce enzymes that effectively break down though plant materials like lignin [54,55,56]. Monomitic systems comprised entirely of generative filaments, while dimitic systems include generative and skeletal hyphae. Trimitic systems incorporate all three types of hyphae. Research by Bayer and McIntyre’s indicates that monomitic mycelial networks exhibit lower structural integrity compared to dimitic and trimitic systems [57,58]. For instance, the trimitic system in Trametes versicolor demonstrated superior tensile and flexural strength compared to the monomitic system in Pleurotus ostreatus when cultivated on rapeseed straw [27]. However, many studies fail to specify the fungal species used in composite production, thus hindering reproducibility due to the omission of mycelium network details [41,59,60,61]. Moreover, according to Aiduang et al. (2022) [62] , the genus Pleurotus leads in MBC production, accounting for 25.0% of total production, followed by Ganoderma (22.2%), Trametes (18.1%), and Pycnoporus (4.2%). Other contributors include Polyporus, Agaricus, Coriolus, and Lentinula, each at 2.8% (Figure 1).

2.2. Substrates

Agricultural waste streams consist primarily of lignocellulosic materials, including cellulose (35-50%), hemicelluloses (20-35%), and lignin (10-25%) [63,64]. These proportions vary depending on plant species, tissue type, and plant maturity The global generation of agricultural waste has been increasing rapidly due to human activities, with a growth rate of 5–10% per year [65,66]. By 2025, global agro-industrial residues are projected to reach 2.2 billion tons annually [67,68]. Poor management of these residues poses environmental and health risks, including greenhouse gas emissions and water contamination, making agricultural waste a critical focus of scientific research [69].

Mycelium growth relies on substrates made from a blend of agricultural crop residues, which provide the necessary nutrients and conditions for fungal development [18,46]. Common substrates include rice husk, coconut husk, sawdust, and potato dextrose broth, all rich in cellulose [70] as well as banana fibres [71]. Rice bran, for example, has larger particles but retains more water due to its finer components [70]. Mycelium-based materials utilise lignocellulosic waste as a substrate, taking advantage of fungi’s natural ability to break down cellulose and lignin found in plant biomass [62].

A comprehensive summary of research on MBC research from the past decade is presented in Table 1, with data collected using keywords from Web of Science and Google Scholar.

Haneef et al. [40] highlighted that a substrate combining refined cellulose and potato dextrose broth (PDB) in a 1:1 weight ratio is ideal for cultivating mycelium. Cellulose, abundant in hardwoods and crop residues, provides essential structural material, while PDB, abundant in simple sugars, is readily metabolised by mycelium as an energy source. This mixture creates a consistent substrate, enabling uniform mycelium growth and producing a homogenous material [14,127].

Since hyphae extract nutrients directly from the substrate, its composition significantly impacts mycelium growth [101]. Adding nutrient supplements can further promote growth, while fungal taxa and isolates vary in their capacity to degrade and colonise substrates based on lignocellulosic enzyme production [128]. Environmental parameters, including light, humidity, pH, temperature, and incubation duration also play key roles in mycelial growth, colonisation and structural properties of the final products [103,129,130].

Selecting the appropriate substrate is critical, as different fungal species thrive on specific materials, which directly affects composite development. The substrate not only supports fungal growth but also determines the mechanical characteristics of the final mycelium panel [91,131].

Mycelium forms a network that secretes enzymes to break down substrate polymers, converting them into nutrients and minerals needed for growth. This process produces a compact fungal layer over the substrate, influencing the chemical, mechanical, and physical characterisations of macromycetes [18,129]. As the mycelium degrades and colonises the substrate, it uses the nutritional compound to extend and densify its hyphal network. For optimal growth, the substrate must provide Carbon, Nitrogen, minerals, vitamins, and water. Based on the fungal strains, the degradation process may preferentially target cellulose or lignin, although hemicellulose is commonly broken down by all species. These preferences are influenced by species-specific traits and environmental conditions [28,60,81].

2.3. Fungal Growth Conditions: Moisture Content and Temperature

Temperature and humidity significantly influence mycelium development. Optimal growth occurs at room temperature (24–25°C) [132], with high humidity levels, often maintained using humidifiers or sprinkler systems. Jiang et al. (2017) [41] used semi-permeable polypropylene bags to create sterile environments with up to 98% relative humidity, ideal for mycelium cultivation. Similarly, Attias et al. [25] incubated Colorius sp., Trametes sp., and Ganoderma sp. on woodchips at 23°C and 95% relative humidity for a 14-day period prior to oven drying [25].

Naturally grown mycelium contains over 60% water [21], which must be reduced to halt growth improve mechanical properties. While specific final moisture content is underreported, it must be low enough to prevent fungal regrowth [46]. Moisture content varies by substrate and fungal species; for instance, hemp pulp retains more moisture than cotton wool [60]. Coatings also affect moisture absorption. Before deactivation, moisture content typically ranges from 59% [133] to 70–80% [134], while the final residual moisture is approximately 10–15% [134]. This residual moisture level is critical for the mechanical performance of MBC.

2.4. Growth Profile and Biomass Fabrication

Fungal bio-composite production begins with substrate colonisation, which can be shaped either during or after mycelial growth. Once colonised, the material undergoes pressing and drying under controlled pressures and temperatures [135]. Most solid bio-composites use agricultural plant waste as a substrate, though one study used chicken feathers [136]. Forestry waste, including wood, fruit tree and bamboo fibres, is also common. Some patents propose wool and silk as alternative substrates [137].

Substrates must first absorb water to support fungal growth, with hydration times varying by material [21,138]. Although hydration time varies by substrate, pre-soaking for at least 48 hours is generally required to achieve full water absorption and support fungal growth [139,140]. Once hydrated, raw materials are homogenised – via blending, grinding, or milling – to increase the surface area for fungal colonisation [21,84]. To prevent contamination, the substrate is sterilised before inoculation, usually via autoclaving, which maintains hydration. Alternative sterilisation methods include oven drying, which may excessively dehydrate the substrate, and hydrogen peroxide (H2O2) treatment, which is energy-efficient but more prone to contamination and less effective [141].

After sterilisation, the substrate is mixed with fungal inoculum and placed in a mould. A 10-day incubation period allows mycelium facilitating substrate cohesion, forming a 3D network of fungal and plant fibres (Figure 3). Initially, the material contains about 70% water. Once moulded, it is oven-dried to stop mycelium growth. Water evaporation during drying creates microscopic air pockets, resulting in a rigid, closed-cell foam structure [82]. Figure 2 outlines the mycelium composite production cycle, highlighting key stages, their purpose, and process variations.

Fungal is used to create mycelium composites by shaping lignocellulosic materials into 3D moulds [11,142]. These materials are inoculated with 10-32 wt% fungal-derived biomass, including spores suspended in a fluid medium or hyphal/fruiting body tissues cultivated on the cultivation matrix enriched with nutrients like wheat grains [11,143]. Spores disperse uniformly, promoting even colonisation, though they initially struggle on low-quality materials. This limitation can be overcome by first growing on nutrient-rich substrate like grain or sawdust, before transitioning to lower-grade substrates, which results in fewer initiation points and uneven distribution [84].

After inoculation, moulds are incubated at room temperature or in controlled environments (25-27 °C) for periods ranging from days to months, contingent on the fungal strains, substrate, and desired material properties [144]. Room temperature incubation is more energy-efficient but slower than high-temperature conditions.

Post-incubation processes include heat-pressing [18,81] and Integrating a composite woven-textile layer with a mycelium-derived foam core [86]. These methods stiffens the composite, halt fungal growth, and enhance mechanical performance [143]. In industrial settings, heat-pressing and oven drying are preferred for rapid dehydration and material densification. Another method was also employed for MBC preparation. In this approach, the mixture of substrate and fungal strains was placed into moulds and subjected to cold pressing. The moulds were then incubated for three weeks. After 21 days, the synthesised composites were removed and incubated outside the moulds for an additional week. The resulting specimens were thereafter oven-dried at 70 °C for 72 hours [126].

Final mycelium composites are biodegradable, typically composed of ~95 wt% lignocellulosic material bound by ~5 wt% fungal mycelia (based on ergosterol concentrations of ̴870 ppm, equating to 50 mg biomass per 1 g of wheat grains cultivated over seven days [145]. Adjusting water content during fabrication significantly impacts mechanical properties. Research by Appels et al. (2019) [18] highlights that pressing expels water and air, reducing porosity, increasing density, and improving Young’s modulus and strength [146,147,148]. Pressing also reorients fibres, enhances fibre connections, and minimises voids that could cause structural defects [149,150]. Hot pressing, which applies both pressure and heat, further strengthens the material compared to cold pressing [18].

Figure 3. (A) The typical composition of mycelium-based foam, adapted under a Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License [36]. In commercial applications, mycelium composites are used as: (B) substitutes for particleboard in wall panelling and door cores; (C) flexible insulation foams, under the terms of the Creative Commons CC-BY license [27]; and (D) composites made by growing fungal mycelium on locally sourced vine pruning waste. The mycelium thoroughly colonises the plant substrate, resulting in a natural bio-composite foam, adapted with permission from [135]. There is no scale bars provided in the references.

Figure 3. (A) The typical composition of mycelium-based foam, adapted under a Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License [36]. In commercial applications, mycelium composites are used as: (B) substitutes for particleboard in wall panelling and door cores; (C) flexible insulation foams, under the terms of the Creative Commons CC-BY license [27]; and (D) composites made by growing fungal mycelium on locally sourced vine pruning waste. The mycelium thoroughly colonises the plant substrate, resulting in a natural bio-composite foam, adapted with permission from [135]. There is no scale bars provided in the references.

3. Properties

Scientific studies evaluate mycelium composites through physical and mechanical tests, including density, compressive and flexural strength, heat resistance, water vapor transmission, moisture uptake, and dimensional stability [142]. Additional properties, such as acoustic insulation [81,151] and antibacterial benefits [14,60,78], are also documented. Table 2 compares the general characteristics of MBC, bacterial cellulose (BC)-reinforced MBC, and other materials.

3.1. Mechanical Properties

The mechanical properties of MBC are essential for engineering applications, with the fungal species and substrate significantly influencing their network structure and resulting strength variations[157].

3.1.1. Tensile Strength

Tensile strength, a key performance metric of MBC, ranges from 0.01 to 1.55 MPa (Table 3), and depends on the mycelium binder network [18,57,58,158]. Processing methods also impact tensile strength, particularly in construction applications [8]. For example, MBC made with T. versicolor (trimitic hyphal system) on rapeseed straw exhibited greater tensile strength (0.04 MPa) than P. ostreatus (monomitic hyphal system) on the same substrate (0.01 MPa), due to the more complex, highly branched trimitic network [18,158]. Pressing techniques further enhance tensile properties, with heat-pressing yielding the highest strength, succeeded by cold and/or non-pressing techniques [151,158,159]. A P. ostreatus composite cultivated on a cottonseed hull substrate reached 0.13 MPa with hot pressing (at 150°C, 30kN), compared to 0.03 MPa with cold pressing (20°C for 20 minutes, followed by drying) [18] . MBC tensile strength is comparable to polystyrene foam (0.15–0.7 MPa) [27].

3.1.2. Compression Strength

Compressive strength, a key mechanical characteristic, evaluates a material’s capacity to resist compressive loads and is crucial for functional applications [46]. Several factors influence the compressive strength of MBC, including substrate formulation, fungal species, processing techniques, porosity, and pressing degree [18]. MBC compressive strength ranges from 0.03 to 4.44 MPa (Table 3), varying with substrate type [21,159,160,161].

Zimele et al. [19] assessed MBC for building materials, finding that hemp-based (0.36 MPa) and wood-based (0.52 MPa) MBC exhibit compressive strengths comparable to cemented wood wool (0.3 MPa) and hemp concrete (0.36 MPa). MBC made from pine sawdust with Pycnoporus sanguineus showed higher strength than those with Peniophora albidus [91]. However, mycelium-based foam (MBF) from wheat stalks and Pleurotus species had lower compressive strength than synthetic polymer foams due to higher water absorption [162]. Pultrusion has been suggested to improve the compressive strength of hemp-based MBC. [163].

Material composition also affects performance. Silverman (2018) [164] found that adding psyllium husk fibres enhanced MBF strength, while chicken feathers were also tested as reinforcements. MBC from Ganoderma lucidum cultivated over rapeseed cakes and oat husks outperformed those from Agaricus bisporus and Pleurotus ostreatus on the same substrates [160]. G. resinaceum MBC on rose flower waste (1.03 MPa) had greater compressive strength than on lavender straw (0.72 MPa) [104]. Ghazvinian et al. [38] reported that P. ostreatus MBC cultivated over sawdust (1.02 MPa) was significantly stronger than colonised on straw (0.07 MPa). Additionally, Trametes versicolor MBC performed better when the fungus was grown on hemp than on pine or flax [21].

Increasing pressure during fabrication has been shown to improve compressive strength [159,165]. Ensuring adequate compressive strength is crucial for MBC applications in packaging and building industries, as weaker materials pose structural limitations [8].

3.1.3. Flexural Strength

Flexural strength, or modulus of rupture or bend strength, measures the stress at which a material fractures under bending [158]. In MBC, flexural strength is influenced by porosity (negatively), density (positively), and mycelium particle size [166]. Table 3 summarises the MBC flexural strength ranges from 0.05 to 4.40 MPa.

MBF generally has lower flexural strength than synthetic polymer foams and pulp fibre foams of similar density, though its tensile strength is significantly higher [162,167]. However, MBC made from Trametes (T.) versicolor and Pleurotus (P.) ostreatus on rapeseed straw and beech sawdust exhibited greater flexural strength than synthetic foams. T. versicolor, with its trimitic hyphal network, produced stronger MBC (0.22 MPa) than P. ostreatus, which has a monomitic hyphal system (0.06 MPa) [18].

Substrate composition also plays a key role in MBC bending strength [168]. Fibrous straw-based composites outperformed cotton fibre composites, while beech sawdust composites had the highest flexural properties (flexural modulus: 9 MPa, flexural strength: 0.29 MPa) due to their dense mycelium network and continuous microstructure [82]. Incorporating 2.5% nanocellulose to a lignocellulosic substrate improved flexural strength from 1.5 to 3.5 MPa [88].

Jiang et al. (2017) [41] examined different fibre types in MBC and found that flax fibres provided better mycelium colonisation and bonding than jute or cellulose. Flax-based composites had nearly double the ultimate strength (35 kPa) and yield stress (27 kPa) compared to jute (20 kPa, 12 kPa) and cellulose (16 kPa, 15 kPa) [41].

3.2. Physical Properties

3.2.1. Density

The density of MBC varies significantly across studies owing to variations in substrate type, fungal strains, and pressing methods [127,171]. Generally, higher density correlates with increased Young’s modulus and strength, as seen in the majority of porous materials [157].

Substrate composition plays a key role in determining MBC density. Composites made from grain-, fibre-, husk-, or wood pulp-rich substrates tend to have higher densities [172,173]. Fungal species also influence density due to variations in lignocellulose degradation, which alters biomass composition [18,171]. For example, A. bisporus, G. lucidum, and P. ostreatus cultivated over rapeseed cake produced denser MBC than those on oat husks [160]. Similarly, Pycnoporus sanguineus colonised on pine sawdust resulted in higher-density composites than those from coconut powder [91,174]. Table 4 summarises reported MBC densities, ranging from 25 to 954 kg/m³.

Pressing techniques significantly increases final MBC density. Heat pressing has been shown to triple density, while cold pressing doubles it, compared to non-pressed MBC from P. ostreatus and T. versicolor [18,21,159,175]. However, achieving consistent density and homogeneity in MBC remains a challenge for large-scale applications [160,175].

3.2.2. Water Absorption Rate

MBC are highly hygroscopic, meaning their water absorption rates are measured by comparing dry and post-moisture exposure weights [19]. This property is critical for structural applications, especially in construction [165]. Water absorption capacity is influenced by substrate density, with denser substrates generally absorbing less water [160]. This variation affects MBC durability in moisture-exposed environments [21].

The fungal species and substrate type also influence water absorption. Substrates made from wood, coconut, and fibre materials typically retain more moisture [177]. For example, T. versicolor absorbs 26.8% and 30.3% water in wheat straw and flax, respectively, but 436% in rapeseed straw. Ganoderma lucidum on beech sawdust exhibits notably low absorption (6%) due to the hydrophobic characteristics of its hyphal walls, whereas Ganoderma fornicatum and Ganoderma williamsianum represent high water uptake in corn husk, rice straw, and sawdust [177].

Water absorption is also affected by the mycelium’s outer hydrophobic layer. Higher-density mycelium layers reduce absorption, as seen in MBC from hemp substrates compared to flax and straw [21]. Similarly, MBC from G. resinaceum and rose flower waste (density: 462 kg/m³) absorbed less water (43.9%) than those from lavender straw (114.6%, density: 347 kg/m³) [104]. P. ostreatus MBC on sawdust (330 kg/m³) absorbed less water than those on sugarcane bagasse (110 kg/m³) [93]. Smaller substrate particles reduce absorption by increasing density and minimising voids [18].

Compared to polymer-based materials (0.01 to 9%) [27,178], MBC absorb significantly more water due to their cellulosic fillers and porous mycelium binder [179,180,181]. This remains a significant challenge for MBC applications in humid environments [8]. Strategies to mitigate water absorption include pressing techniques, granular fillers, and bio-derived coatings. Polyfurfuryl alcohol resin (PFA) has shown potential for improving water resistance in organic fibre composites [182], and chitosan coatings significantly reduce water uptake compared to carrageenan and xanthan coatings [162,183].

In one study, MBC from bamboo sawdust and corn pericarp were submerged in water for 96 hours [1]. As can be seen from Figure 4, the bamboo MBC absorbed 170.70%-224.08% water, stabilising after 48 hours, while corn pericarp MBC absorbed 104.89% to 139.22%, stabilising at 60 hours. Among bamboo composites, Schizophyllum commune had the highest absorption, while Lentinus sajor-caju had the least. Within corn pericarp composites, G. fornicatum absorbed the least water (Figure 4) [1].

3.2.3. Acoustic Absorption Behaviour

MBC are highly effective at absorbing sound, converting air molecule vibrations into heat and reducing noise buildup in enclosed spaces [27]. Some MBC, such as those colonised on rice straw (52 dBa), hemp pith (53 dBa), and flax shive (53.5 dBa), outperform traditional sound absorbers like commercial ceiling tiles (61 dBa), urethane foam board (64 dBa), and plywood (65 dBa) [27].

Acoustic performance in MBC is influenced by porosity, tortuosity, flow resistivity, and pressing conditions [81]. Pelletier et al. (2013) [81] found that MBC made from cotton bur fibre, flax shive, hemp pith, kenaf fibre, rice straw, sorghum fibre, and switchgrass achieved 70–75% sound absorption at 1000 Hz. This makes them competitive alternatives to fibre boards (11–31%), polystyrene foams (20–60%), polyurethane foams (20–80%), plywood (10–23%), and softwood (5–15%) [27,184].

A 2022 study examined the acoustic characteristics of a T. versicolor MBC with yellow birch wood particles [185]. Maximum sound absorption coefficients exceeded 0.5 Hz across all samples, with the highest value (0.87 at 2800 Hz) observed in composites incubated for six days (Figure 5). Longer incubation periods led to increased porosity but reduced sound absorption. This effect was linked to mycelium growth gradually filling air gaps between wood particles, altering airflow resistance and reducing pore sizes, which affected sound transmission (Figure 5) [99].

Due to their strong acoustic absorption, MBC serve as sound-insulating materials, in walls, doors, and ceilings of concrete halls and broadcasting studios [27,184]. However, pressing methods (hot or cold) can reduce sound absorption efficiency, making them unsuitable for MBC intended as sound absorbers [186].

3.2.4. Thermal Conductivity/Degradation

MBC are effective natural thermal insulators because of their poor heat transfer properties, high porosity, low density, and significant air content [175,187]. Their thermal conductivity varies based on density, moisture content, and fibre type [27], ranging from 0.05 to 0.07 W/m·K—equale to traditional insulation materials like glass wool (0.04 W/m·K), extruded polystyrene (0.03 W/m·K), sheep wool (0.05 W/m·K), and kenaf (0.04 W/m·K) [24,188]. MBC made with wheat straw and various mycelium species demonstrated heat transfer properties between 0.074 and 0.087 W/m·K, reinforcing their potential as sustainable insulators [85]. Sustainable composite insulators also contribute to reducing buildings’ environmental impact [189]. Dias et al. (2021) [189] examined a self-growing biocomposite made from Miscanthus × giganteus and mycelium, finding thermal conductivities between 0.0882 and 0.104 W/m·K, similar to straw (0.08 W/m·K) [190], hemp concrete (0.1 W/m·K) [187], softwoods (0.12 W/m·K) [191], biochar-doped wheat gluten (0.096 W/m·K) [192], and gypsum (0.17 W/m·K) [191].

MBC undergo thermal degradation in three stages: initial water evaporation (25-200 °C, 5% weight loss), major degradation (200-375 °C, ~70% weight loss), and decomposition starting at 280 °C-290 °C [193]. Their degradation range (225-375 °C) aligns with lignocellulosic materials (220-450 °C) [26,91,171,193,194]. Adding silica (SiO2) and glass fines significantly improves MBC’s thermal resistance and fire-retardant properties [84]. Glass fines, in particular, extended flashover time from 94 to 370 seconds in wheat grain-based composites and from 75 to 311 seconds for rice hull-based composites [84,193]. Furthermore, furfurylation (treatment with furfuryl alcohol) reduced the fire growth rate index of wood-based MBC from 15.17 to 1.99 (kW/m2.s) [195].

Mycelium exhibits better fire resistance than thermoplastics like polymethyl methacrylate (PMMA) and polylactic acid (PLA) due to its higher char yield [193,196]. It improves the fire resistance of wheat grain composites [84], though extending its growth period beyond six days has minimal effect on fire properties [193]. The thermal degradation behaviour of mycelium varies with temperature because of simultaneous chemical and thermal processes. Initially, up to 100°C, no heat is released, indicating a non-combustion phase driven by water loss [193,194]. Between 100°C and 200°C, heat release increases as flammable volatiles are emitted [193]. Thermogravimetric analysis (TGA) of MBC (Figure 6) [1] confirms a three-phase degradation pattern, similar to lignocellulosic substrates but with a more rapid weight loss rate [18,91].

3.2.5. Shrinkage

Shrinkage is a key physical characteristic of MBC, primarily caused by dehydration during drying [21]. Lower shrinkage improves strength and shape stability. A 2024 study found that MBC from bamboo sawdust had lower shrinkage (3.14% to 5.83%) than those from corn pericarp (9.80% to 16.66%) across various fungal species [1]. L. sajor-caju on bamboo sawdust MBC showed least shrinkage, while S. commune on corn pericarp MBC showed the highest [1]. Moisture content and drying methods also influenced shrinkage [18,21].

These findings align with previous studies, which reported MBC shrinkage between 2.78% and 17% [113,142,197,198,199]. Notably, MBC using bamboo sawdust consistently showed lower shrinkage, highlighting the role of substrate selection in minimising shrinkage [21,142]. In another study, MBC from rice straw had the maximum shrinkage, followed by corn husk and sawdust, regardless of fungal species (Figure 7) [113]. S. commune consistently had the highest shrinkage across substrates, while L. sajor-caju had the lowest, though not significantly different from Ganoderma fornicatum and Ganoderma williamsianum. These results suggest potential for MBC as alternatives to wood insulation boards [113].

MBC from Pleurotus sp. on wheat residue had a shrinkage value of 6.2% [142], while Elsacker et al. (2019) [21] reported higher shrinkage for T. versicolor MBC on pine softwood waste (15%), flax (10%), and hemp (9%), emphasising the impact of substrate choice. Compared to polymer-based materials like nylon, polystyrene, and polypropylene (0.3% to 2.5% shrinkage) [200], MBC exhibit a broader shrinkage range, similar to wood-based materials (1% to 25%) [201,202].

4. Scanning Electron Microscopy Analysis

Mycelium composites exhibit complex surface topography, best analysed using Scanning Electron Microscopy (SEM) to examine their morphology and structural characteristics [203].

A study on mycelium-Miscanthus composites (sample G0.7_M1_P0.5) utilised SEM to analyse Ganoderma resinaceum mycelium, Miscanthus fibres, and potato starch using SEM [189]. Miscanthus fibres displayed an anisotropic structure with aligned hollow tubes, while mycelium formed an interconnected filament network. In the composite, mycelium enveloped the Miscanthus internally and externally, though the penetration depth remained unclear. Voids observed in the SEM images suggested potential variations in mechanical properties (Figure 8) [189].

SEM analysis of MBC revealed that fungal mycelia uniformly covered all composite surfaces (Figure 9A–L). L. sajor-caju exhibited higher mycelial density across various substrates. Cross-sectional images showed mycelial filaments interconnecting substrate particles, with entrapped air pockets within the composites (Figure 9M–O) [113]. These findings align with previous studies [18,171]. In contrast, uninoculated substrates lacked both fungal mycelium and entrapped air pockets (Figure 9P–R) [113].

Islam et al. (2017) [13] used SEM to analyse fibre arrangement, revealing an irregular microstructural network with randomly oriented fibres. The average hyphae diameter was 1.3 ± 0.66 µm [13].

5. Fourier Transform Infrared (FTIR) Spectroscopy

FTIR spectroscopy is commonly used to gather information about the chemical and structural characteristics of MBC. The resulting spectra also provide valuable insights into the functional groups and molecular identifications of the substrates and final composites. In a recent study by Hu and Cao, FTIR was employed to analyse the chemical composition of the substrates and manufactured panels [204]. As illustrated in Figure 10, FTIR spectra display characteristic peaks and bands corresponding to various functional groups. For example, a broad band around 3410 cm⁻¹ is attributed to O-H stretching vibrations of polysaccharides indicating the presence of cellulose and hemicellulose [46]. Absorption bands observed at 1650 cm⁻¹, are associated with C=O stretching (amide I) and NH₂ groups [205], while the band at 1490 cm⁻¹, corresponds to CH₂ stretching vibrations, indicative of protein content. A notable band at 1325 cm⁻¹ is linked to NH₂ stretching in amines, commonly referred to as amide III [88]. Additionally, the peak detected at 1043 cm⁻¹ is characteristic of C–C vibrations, suggesting the presence of proteins, lignin, and polysaccharides [204].

Another study by Haneef et al. investigated the FTIR spectra of MBC derived from various fungal species, regardless of substrate type. They reported that G. lucidum exhibited a greater presence of lipids, while Pleurotus ostreatus, in contrast, displayed stronger spectral bands likely originating from polysaccharides [40].

Overall, infrared spectroscopy of the mycelium composites highlighted distinct absorption patterns corresponding to their molecular constituents. These included lipids, indicated by absorption bands in the 3000–2800 cm⁻¹ range and around 1737 cm⁻¹ (associated with ester bonds); proteins, with characteristic amide I, II, and III bands observed between 1700–1300 cm⁻¹; nucleic acids, detected around 1255–1245 cm⁻¹; and polysaccharides, showing distinct signals in the 1200–900 cm⁻¹ region [14,91,152].

6. Cost Comparison

The production costs of MBC vary across industries, influenced by feedstock accessibility, manufacturing methods, labour costs, and industry dynamics [165,206]. MBC can be cost-effective due to their reliance on agro-industrial byproducts, energy-efficient manufacturing, and lower ecological footprint. However, precise cost comparisons with traditional materials remain challenging [165].

Osman (2023) [207] estimated construction costs for various building materials (Table 5), Showing mycelium-plywood panels as the most affordable and concrete blocks as the most expensive. Mycelium panel production is estimated at $0.83 per cubic foot [207]. Studies indicate MBC can reduce costs by over 65% compared to paper-derived materials and over 90% versus fabric composites, gypsum, polymers, and wood-PHA composites [165,208,209]. However, savings depend on application, production scale, and regional factors [210]. Additionally, MBC costs are comparable to cement-derived materials [211]. These economic advantages, mostly in material sourcing, production, and waste reduction, make MBC a competitive alternative in various industries [207].

7. Termite Resistance

Termites cause extensive structural damage worldwide, amounting to billions of dollars annually [212]. While most prevalent in Africa, Asia, South America, and Australia, they also impact North America, with New Orleans alone experiencing over $100 million in damage each year just in New Orleans [213]. MBC, composed mainly of lignocellulose, are naturally susceptible to termites. However, resistance can be enhanced by optimising substrate composition and applying natural or commercial termiticidal treatments [214,215].

Research shows termites predominantly degrade the base of MBC samples rather than the sides or top [214]. Termiticide efficacy correlates with termite mortality, with higher mortality indicating stronger repellence. Vetiver oil, cedar oil, and guayule resin exhibit varying degrees of repellence [214]. Among tested biocomposites, hemp-based MBC demonstrated the highest resistance and lowest loss over four weeks (16–53 wt%), while kenaf-based MBC showed medium to high resistance but higher mass loss (43–62 wt%), depending on the mycelium strains. Corn-based MBC had lower termite resistance, moderate mortality rates, and mass loss of 42–43 wt% [214].

Guayule resin, rich in flavonoids, cinnamic compounds, terpenoids, and p-anisic acid [216], and vetiver oil, containing α- and β-vetivone compounds [217], are highly effective natural termiticides. A single-layer treatment with these oils ensures total termite mortality and significantly reduces mass loss in treated MBC (18–28 wt% for guayule resin and 16–27 wt% for vetiver oil), compared to untreated MBC (42–62 wt%) and untreated southern yellow pine (80 wt%) [217].

8. Life Cycle Assessment

MBC are biodegradable, cost-effective, and grow on readily available substrates [5]. In contrast, traditional construction materials contribute to pollution by releasing harmful emissions during production [5]. This highlights the importance of evaluating materials through life cycle assessment (LCA), which analyses environmental impacts from production to disposal [46].

Challenges in MBC production include precision in drying, forming, and cutting, as identified in 2016 [206]. Durability is another concern, with studies suggesting mycelium bricks may last less than 50 years [218]. Research is needed to enhance longevity while maintaining biodegradability. Despite these challenges, MBC exhibit substantially lower embodied energy compared to traditional materials – up to 80 times more sustainable than concrete [155]. Their eco-costs are also lower, as they utilise organic waste for production [5]. Table 6 compares lifespan, fossil energy demand, climate impact, and eco-costs of various building materials.

Manufacturing of MBC has a lower ecological footprint compared to materials such as, extruded polystyrene and rockwool [219]. However, of its dependence on biogenic resources, such as hemp and sawdust, affect its properties. To minimise environmental impact, using locally sourced biogenic waste is recommended. While MBC’s end-of-life impacts remain understudied, wood-fibre and straw panels currently have lower climate change impacts [219,221]. Nonetheless, MBC requires less fossil energy than any traditional insulation materials and holds potential for application beyond construction, including packaging, furniture, and fashion [219]. Figure 10 illustrates the production and life cycle of MBC.

Figure 11. The life cycle of mycelium-based materials. Created with BioRender.com.

Figure 11. The life cycle of mycelium-based materials. Created with BioRender.com.

Unlike some novel substitutes for traditional structural materials, such as fibre-reinforced polymer (FRP) bars, which require costly waste disposal methods or complex recycling processes [222], MBC can be easily recycled. Alaux et al. (2024) [223] examined MBC’s end-of-life scenarios, comparing incineration to partial recycling, where 70% of panel mass replaces beech sawdust in in new product cycles. Industrial-scale production reduced most environmental impacts, including a 45% decrease in global warming potential (GWP), but increased terrestrial ecotoxicity. The main contributor to residual greenhouse gas (GHG) emissions were electricity consumed from mixed energy sources. Adjusting energy inputs in manufacturing could reduce GHG emissions by 64% [223]. Previous studies show that transitioning to renewable energy in production and supply chains can lower emissions for insulation materials by up to 83% [224,225,226].

9. Future Directions and Outlook

Fungi have long played a significant role in medicine, biotechnology, construction, and food production. Research into mycelium and its composite materials offers valuable insights into fungal network structures and their biological functions. Further studies can drive eco-friendly, lightweight, and mechanically robust composites [41,46,142]. This review integrates both experimental and simulation-based approaches to support these advancements. Recent research and commercialisation have highlighted the extensive potential of MBC. They are being explored for use in packaging [22,142,227], thermal insulation [21,85,142,228], consumer electronics [229], acoustic absorption foams [81,184], and fire-resistant applications [84,230]. Additionally, they are being integrated into construction for panelling, flooring, and furnishings [231,232,233]. Their water absorption properties make them promising for superabsorbent materials [234,235,236], while their natural hydrophobicity suggests applications in coatings [14,84] and textiles [237,238]. Mushroom residues have recently been used in the production of cosmetic facial masks due to their antioxidative characteristics [239].

Mycelium also contains valuable biopolymers, including chitin, chitosan, and β-glucan, which can be extracted and used in 3D-print, cellulose nanocomposites, films, sheets, and nano-papers [12,240,241]. This could lead to sustainable alternatives for synthetic polymers in filtration membranes [242,243], printed circuit boards [244], and sports equipment [136,245]. Several methods can be applied to improve the physical and mechanical properties of MBC. Some of promising techniques that have been successfully applied to nanocomposites involve impregnating them with kombucha bacterial cellulose, resin and nanofibrillar cellulose, leading to increased stiffness, tensile strength, and thermal conductivity [246,247,248], a similar approach could be explored to improve MBC. Additionally, advanced manufacturing techniques like extrusion and pultrusion could enhance the production of the bio-composites [249,250,251].

Beyond materials science, mycelium networks play a critical ecological by facilitating communication and nutrient exchange among plants, supporting pest and disease resistance [252,253,254]. In sustainable agriculture, fungi function as biocontrol agents, promoting plant while reducing reliance on chemical pesticides, fungicides, and fertiliser [255]. Their use in microbial inoculants offers a cost-effective, eco-friendly alternative to chemical treatments [255,256].

Additionally, fungi can help degrade persistent organic pollutants due to their secretion of lignolytic extracellular enzymes and acidic metabolites [257]. Introducing fungal inoculants can enhance crop yields, soil health, and plant resilience against stressors like salinity, drought, and temperature fluctuations. As key components of the plant microbiome, fungi contribute to sustainable agriculture by supporting ecosystem balance and phytobiome engineering for improved crop production [258].

10. Conclusion

Mycelium cultivation offers an energy-efficient bio-fabrication approach for repurposing agricultural residues into eco-friendly substitutes for synthetic building materials. These include acoustic and thermal insulation, door cores, panelling, flooring, cabinetry, and furnishings. Different applications require tailored properties: high porosity and low density for acoustic and insulation, and scratch resistance, flexural strength, and stiffness for structural components. The environmental benefits and versatility of MBC make them increasingly sought after.

This review examines MBC fabrication, physical and mechanical properties, cost-effectiveness, and life cycle assessments. It highlights key bio-fabrication factors, including fungal species, substrate types, and environmental conditions (temperature, moisture, aeration) and their influence on the material properties. MBC excel in thermo-acoustic insulation, with thermal conductivities equal to or lower than commercial insulators and superior sound absorption compared to ceiling tiles, polyurethane foams, and plywood. Moreover, these composites offer enhanced fire resistance over traditional materials like extruded polystyrene and particleboard, as well as natural termite resistance.

Despite these advantages —low cost, biodegradability, safety, and minimal environmental impact—MBC face challenges, including low mechanical strength, weathering susceptibility, scalability issues, limited lifespan (<50 years), and a lack of standardised manufacturing/testing methods. Overcoming these obstacles is essential for broader adoption. This review provides a comprehensive resource for researchers entering the field, offering insights into MBC production and potential applications.