WO2025125493A1

WO2025125493A1 - A method of producing a composite material

Info

Publication number: WO2025125493A1
Application number: PCT/EP2024/086028
Authority: WO
Inventors: Jon Wedersøe STRUNGE
Original assignee: Naturpladen Aps
Current assignee: Naturpladen Aps
Priority date: 2023-12-12
Filing date: 2024-12-12
Publication date: 2025-06-19
Anticipated expiration: 2026-06-12

Abstract

The present invention relates to a method of producing a composite material and to a composite material. The composite material is obtainable in the method of the invention. In the method, a wood-decaying fungus forms a mycelium across an interfacing surface between hollow plant stems and lignocellulosic material arranged in layers to form the composite material.

Description

A METHOD OF PRODUCING A COMPOSITE MATERIAL

Technical field

The present invention relates to a method for producing a composite material and a composite material manufactured in the method. The composite material comprises a mycelium of a wood-decaying fungus and a lignocellulosic material.

Background

The provision of construction materials has an excessive environmental impact, and there is a need to lower this impact. For example, the production of concrete necessarily involves formation of large amounts of CO2 being released to the atmosphere, and obtaining timber can lead to deforestation. White-rot fungi have been used to manufacture sustainable composite materials by letting a fungus grow and form a mycelium on waste materials originating from trees or from rapid renewable plants, e.g. crops or residues from crops, from agriculture, thereby enabling new application for the much-underutilised plentiful raw materials as well as locking the sequestered carbon into biodegradable materials.

For example, in EP 2 094 856 Bl a method is provided for the culturing of filamentous fungi for the production of materials and composites composed of hyphae forming a network of interconnected mycelia cells through and around substrate particles. In the composites, particles such as fibres, meshes, rods, elements and other bulking agent are used as an internal component, and the hyphae, other cellular tissue and extra cellular compounds act as a bonding agent and as a structural component. EP 2 094 856 Bl does not disclose how to provide properties of a structure in which stability, acoustics absorbance, heat insulation, and efficiency of production are secured through the growth of filamentous fungi.

WO 2019/246636 discloses a composite matrix with macroscopic air spaces which includes non-nutrient discrete particles and mycelium. The composite matrix is also described as a composite biomaterial, and the product is a low-density, hydrophobic, high porosity myceliated material that is biodegradable and non-toxic to produce, handle and dispose of. Applications of the product include as an insulation mat; a biological tissue substitute or scaffold; substitution of non- biodegradable and/or petroleum based foams.

Methods of the prior art are generally limited with respect to the geometrical dimensions available to fungal based composite materials as the fungi need air to grow. The present invention aims to provide additional and improved fungal based composite materials.

Summary

With this background it is therefore an object of the invention to provide a composite material and a method for producing the composite material. The invention especially aims to provide a composite material suitable for insulation or as an acoustic material. This and further objects are met in the following aspect:

A method is provided of producing a composite material, the method comprising the steps of:

- providing a plurality of hollow biodegradable members and arranging the hollow biodegradable members in at least one air transporting layer;

- providing a lignocellulosic material and arranging the lignocellulosic material in at least one substrate layer;

- wetting at least one of the air transporting layer and the substrate layer with water;

- alternatingly stacking the air transporting layer(s) with the substrate layer(s) to form an incubation stack, the incubation stack comprising interfacing surfaces between the hollow biodegradable members and the lignocellulosic material;

- inoculating at least one of the air transporting layer and the substrate layer with a wood-decaying fungus;

- allowing the wood-decaying fungus to form a mycelium across at least one interfacing surfaces to form the composite material.

In another aspect, the invention relates to a composite material comprising a mycelium of a wood-decaying fungus and at least one layer derived from a lignocellulosic material and at least one layer derived from hollow biodegradable members and an interfacing surface between the hollow biodegradable members and the lignocellulosic material, wherein the mycelium transgresses the interfacing surface.. The composite material is obtainable in the method of the invention. The composite material may have a thickness of at least 2 cm. In general, any example of the present method and its accompanying features and advantages applies equally to the composite material of the invention.

In the method, a wood-decaying fungus is grown on a lignocellulosic material, and during the growth, the wood-decaying fungus forms a mycelium that tightly integrates with the lignocellulosic material to eventually form a solid material, i.e. a composite material. The lignocellulosic material may also be referred to as lignocellulosic biomass, and the lignocellulosic material is generally dry matter obtained from plants. A lignocellulosic material generally comprises carbohydrate polymers, typically cellulose and hemicellulose, and lignin. Lignocellulosic material can generally be described as fibrous materials, where at least the carbohydrates, but also the lignin, alone generally have a fibrous form. Any lignocellulosic material may be used in the method. In the present context, the lignocellulosic material may be classified by its source. For example, the lignocellulosic material may be referred to as lignocellulosic material of a specific plant, e.g. a specific tree, such as a deciduous tree, e.g. beech, oak, birch, maple, aspen, elm, etc., or an evergreen tree, e.g. pine, hemlock, spruce, and fir, or a crop, such as cereal straw, e.g. wheat straw, reeds, hemp or bamboo, etc. It is especially possible to use lignocellulosic materials from different plants. For example, a single layer of the composite material may contain lignocellulosic materials from different plants, or different layers may contain lignocellulosic materials from different plants. In an example, the lignocellulosic material comprises material from two or more sources, e.g. a mixture of wood-derived material, e.g. wood particles, and hemp-derived material, e.g. hemp fibres. It is, however, also contemplated that the lignocellulosic material may have a low content of lignin, and in particular, the lignocellulosic material may comprise material mainly based on cellulose, e.g. cellulose fibres, such as textile. For example, cellulose fibres may be added together with a plant based lignocellulosic material. In an example, the lignocellulosic material comprises a plant material and a textile.

The method includes the steps of forming an incubation stack and inoculating at least one of the air transporting layer and the substrate layer with a wood-decaying fungus. It is to be understood that either or both of the air transporting layer and the substrate layer may be inoculated before or after formation of the incubation stack, and regardless of when the respective layer(s) is/are inoculated, the stack with the air transporting layer and the substrate layer is referred to as an "incubation stack". The incubation stack may be incubated in a chamber to produce a generic mass, e.g. a composite mass. This mass can be used to produce planar or non-planar boards or shapes, e.g. geometrically shaped boards, to produce bespoke architecture by cutting the generic mass in desired thickness, either at dry or wet stage. For example, the composite mass can be used to produce large building components. At wet stage planar cut elements may be placed in or on a geometrically defined shape and dehydrated to obtain the corresponding shape, which may thereby provide a new permanent shape. Alternatively, curing from wet stage to grow several elements together into structures, e.g. whole structures, or multi-layered products. The surface may be heat-pressed at wet stage to improve smoothness and/or to increase its density. At dry stage the surface may be sanded and surface treated.

The method may involve heat treating the incubation stack or the composite material. In general, heating of the incubation stack or the composite material dehydrates the heated material, i.e. the incubation stack or the composite material. Heating, and thereby dehydration, is generally done after fermentation of the incubation stack. It is also contemplated that dehydration may be achieved using other means than heating, e.g. the incubation stack or the composite material may be dehydrated by drying, for example in a well-ventilated environment at ambient temperature or lower. For example, the incubation stack or the composite material may be heated to a temperature in the range of 50°C to 200°C, e.g. 100°C to 200°C, or 150°C to 200°C. The duration of the heat treatment may be selected freely, but in an example, it is at least 15 minutes. In a specific example, the heating involves hot- pressing or heat-pressing the incubation stack or the composite material. In particular, the composite material may be hot-pressed at a temperature in the range of 50°C to 200°C. In the present context, the words "hot-press" and "heat-press", and derived forms, may be used interchangeably.

The present method employs hollow biodegradable members. In the present context, the term "hollow" generally describes a tubular form, although the term is not limited to mean tubular. Thus, the hollow biodegradable members may also be referred to as tubular biodegradable members. The biodegradable member may be made from any material that can be at least partly degraded during the fermentation to integrate the hollow biodegradable member in the composite material produced in the method. The hollow biodegradable members may be hollow plant stems. A lignocellulosic material is also used in the present method. In the present context, the lignocellulosic material is generally referred to as a substrate for wood-decaying fungi, and correspondingly, hollow biodegradable members should also be a substrate for wood-decaying fungi, for example, the hollow biodegradable members may be hollow plant stems, which are typically also formed from a lignocellulosic material. However, it is also contemplated for the present method that the hollow biodegradable members may be made from paper, carboard, a biodegradable polymer, e.g. polyhydroxybutyrate or polylactate. Whenever a hollow plant stem is mentioned in the present document, it is understood to also mean a hollow biodegradable member, and the two terms may be used interchangeably. The hollow plant stems may also be referred to as hollow plant lignocellulosic stems, and the two terms may be used interchangeably. Correspondingly, the plant stems, including the hollow plant stems, can also be degraded by the wood-decaying fungi. Thereby, the wood-decaying fungi can form a mycelium across an interfacing surface between a layer of the lignocellulosic material and a layer of the hollow plant stems. By growing across the interfacing surface, the wood-decaying fungus connects the layers of the incubation stack thereby forming the composite material. The composite material formed in the method is rigid and may also be described as self-supporting. The composite material has properties comparable to a petrochemical foam, such as a foam made from expanded polystyrene (EPS) or to a board made from mineral wool. Thus, the present composite material can be used in any context where an EPS board or a board made from mineral wool would be used.

Many plants form stems when growing and the stems may be hollow or solid. The present method employs hollow plant stems, and for the method, the hollow plant stems may be selected freely from any plant known to form a hollow stem. For example, the hollow plant stems may be obtained from plants commonly cultured. Thus, the hollow plant stems may be obtained from straw of crops, such as cereal straw, e.g. wheat straw, reeds, hemp or bamboo. The hollow biodegradable members, e.g. hollow plant stems, allow transport of air through the hollow biodegradable members, e.g. the hollow plant stems, and by arranging hollow biodegradable members, e.g. the hollow plant stems, in a layer, an air transporting layer is provided, and thus the hollow biodegradable members, e.g. the hollow plant stems, thereby improve the provision of oxygen and water vapour to, as well as the removal of CO2 and also excess heat and other gasses from, a fungus growing from the lignocellulosic substrate. Thereby, the thickness of the composite material can be increased compared to the thickness of a composite board provided by growing a wood-decaying fungus on a lignocellulosic substrate not having an air transport layer. It is also contemplated that the hollow plant stems are replaced with hollow fibres manufactured from a lignocellulosic material, such as cardboard, or that pieces of a lignocellulosic material are arranged to provide air channels in a layer containing the pieces of lignocellulosic material. The lignocellulosic material different from the hollow plant stems is generally in a particulate form with pieces of lignocellulosic material, e.g. pieces being generally flat by having a thickness in the range of 0.5 mm to 2 cm, being selected to provide appropriate air channels, e.g. by having a length in the range of 10 cm to 100 cm or more, e.g. 100 cm to 300 cm, and a width in the range of 0.5 cm to 3 cm or more.

The hollow plant stems are arranged in a layer, i.e. the air transporting layer, but the air transporting layer may also contain further lignocellulosic material. For example, each hollow plant stem may be surrounded by particles of lignocellulosic material, e.g. as an additional substrate for the wood-decaying fungus. The plurality of hollow plant stems is arranged in at least one air transporting layer and thereby creates a system in which the hollow plant stems allow for the transportation of gasses, e.g. O2 to the growing fungus and CO2 away from the growing fungus, because of the plants stems' hollow properties.

The lignocellulosic material is arranged in a substrate layer. The lignocellulosic material should preferably be arranged densely in the substrate layer, and the substrate layer may also be referred to as a dense substrate layer.

A composite material can generally be described as having an extension in X, Y and Z dimensions, where the Z dimension is normally also referred to as a thickness, with the X and Y dimensions representing the length and width, or the width and length, respectively, of the composite material. The X, Y and Z dimensions may be used in the present context to describe the composite material but also to describe the settings during growth of the wood-decaying fungus. The hollow plant stems are generally arranged in the XY plane, and the hollow plant stems may be arranged in any fashion, e.g. depending on the shape of the hollow plant stems. Plant stems generally have an elongate shape that may be curved or approaching a linear shape. The arrangement of the hollow plant stems, e.g. in the XY plane, may be ordered or random. In an example, the hollow plant stems are selected from plants having generally linear shaped stems, e.g. reed, and the hollow plant stems are arranged to be substantially parallel to each other in the XY plane. By arranging the hollow plant stems in an ordered arrangement, especially in the XY plane, the structure of the composite material produced in the present method can be more easily controlled. For example, when the hollow plant stems are in an ordered arrangement, the layer is of greater homogeneity. Moreover, when the hollow plant stems are arranged to be substantially parallel to each other, e.g. when the hollow plant stems are reeds, air transportation to and from the growing wood-decaying fungus is improved. It is also contemplated that the hollow plant stems are surrounded by the lignocellulosic material in the air transporting layer so that the air transporting layer and the substrate layer can be considered integrated with each other. Correspondingly, the interfacing surface is not restricted to follow the XY plane.

The composite material produced in the method has an outer surface. The outer surface preferably corresponds to a substrate layer.

In general, the distance between the hollow plant stems in the air transporting layer, e.g. in a single air transporting layer, may be selected freely, although the distance between two hollow plant stems should not exceed 15 cm, e.g. 5 cm, or 3 cm. In an example, individual hollow plant stems are arranged to be in contact with neighbouring hollow plant stems.

The method also includes arranging the lignocellulosic material in at least one substrate layer, and the substrate layer and the air transporting layer are alternatingly stacked. Thereby, an interfacing surface is provided between a substrate layer and an air transporting layer. In the present context, the interfacing surface may also be seen as the surface of the hollow plant stem in contact with the lignocellulosic material, i.e. lignocellulosic material not being part of a hollow plant stem. Correspondingly, the transgression of the mycelium through the interfacing surface especially involves degradation of the hollow plant stem and integration of the mycelium with the material, e.g. lignocellulosic material, of the hollow plant stem with the lignocellulosic material of the substrate surrounding the hollow biodegradable members, e.g. the hollow plant stem. Thereby, the lignocellulosic material of the substrate layer and the biodegradable material of the hollow biodegradable members, e.g. lignocellulosic material of the hollow plant stems, are efficiently integrated with each other, and thus the composite material is formed. In the present context, the term "alternatingly stacked" means that the hollow biodegradable members, e.g. the hollow plant stems, have a surface in contact with the lignocellulosic material, e.g. particles of the lignocellulosic material, e.g. of the substrate layer. The lignocellulosic material may be the lignocellulosic material of a substrate layer, although the air transporting layer may also contain hollow biodegradable members, e.g. hollow plant stems, having a surface that is in contact with further hollow biodegradable members, e.g. further hollow plant stems, and correspondingly, the air transporting layer may also contain hollow biodegradable members, e.g. hollow plant stems, surrounded by, and being in contact with, other hollow biodegradable members, e.g. hollow plant stems.

The air transporting layer thus comprises hollow plant stems, but the air transporting layer may also comprise lignocellulosic material other than the hollow plant stems. In general, the air transporting layer can be described to have a thickness, e.g. in the Z dimension. The thickness of the air transporting layer may be in the range of the width of a single hollow plant stem to the width of multiple hollow plant stems, e.g. the air transporting layer may comprise reeds and the air transporting layer may comprise from 1 reed to 15 reeds thus providing the thickness of the air transporting layer. The air transporting layer may also be described as having a thickness in the range of 2 mm to 150 mm, e.g. 5 mm to 100 mm, e.g. the thickness of the air transporting layer includes the hollow plant stems and optionally lignocellulosic material between the hollow plant stems allowing the hollow plant stems, e.g. each hollow plant stem, to be in contact with, and surrounded by, the lignocellulosic material of the substrate layer.

The substrate layer may also be described to have a thickness, e.g. in the Z dimension. The thickness of the substrate layer may be measured from a surface of a hollow plant stem of one air transporting layer to the surface of a hollow plant stem of another air transporting layer, or the thickness of the substrate layer may be measured from a surface of a hollow plant stem to an outer surface of the stack of the substrate layer(s) and the air transporting layer(s). The substrate layer(s) may have a thickness in the range of 10 mm to 150 mm, e.g. 50 mm to 100 mm.

The air transporting layer(s) and the substrate layer(s) are alternatingly stacked to form an incubation stack, and the incubation stack comprises interfacing surfaces between air transporting layers and substrate layers. In an embodiment the layers may be stacked in any order of the substrate layer or air transporting layer and the number of air transporting layers is not limited to one air transporting layer in the stack, but e.g. may be arranged with a substrate layer followed by one or more air transporting layers. In general, the substrate layer is limited by its thickness in the Z dimension. When the incubation stack comprises multiple layers of the air transporting layer, each of the air transporting layers may have the same thickness or different thicknesses, e.g. in the Z dimension. Moreover, the air transporting layer may have the same thickness as the substrate layer, or the air transporting layer and the substrate layer may have different thicknesses. At least one of the air transporting layer and the substrate layer is wetted with water, although it is preferred that the substrate layer is wetted, but both of the air transporting layer and the substrate layer may also be wetted with water. The layers may be wetted, e.g. soaked at any time, e.g. before or after stacking to form the incubation stack. By wetting, especially soaking, at least one of the air transporting layer and the substrate layer, the lignocellulose of the substrate and/or the hollow plant stems is prepared for growing the wood-decaying fungus. The term wetting covers that at least a surface of at the air transporting layer or substrate layer is brought in contact with water. For example, water may be added at an amount that is at, or close to, saturation to reach an optimal humidity level of the biomass to support the decay by the wood-decaying fungus. However, it is preferred that the respective layer or the layers are wetted in water. For example, the substrate layer or the air transporting layer may be immersed in water. After wetting, e.g. soaking, the wetted layer, e.g. the air transporting layer or the substrate layer, is preferably drained to remove free water from the layer. The duration of the soaking of the layer(s) is not limited but it is preferred that the time is sufficient for the lignocellulose of the layers to reach a saturation point. By soaking the layers until fibre saturation is reached, access to humidity, and also to the fibres of the lignocellulosic material, is optimised for the wood-decaying fungus to grow. The wood-decaying fungus generally does not require a specific temperature range but will grow at a faster rate at a set ambient temperature. In particular, no added heat is required for the wood-decaying fungus to grow, although the temperature during the growth of the wood-decaying fungus may also be controlled. In particular, the temperature during the growth of the wood-decaying fungus should be kept stable during growth. For Ganoderma lucidum a growth temperature between 25°C and 30°C is ideal. Moreover, as degradation by the fungi enzymes can generate heat and as the degradation of the lignocellulosic or biodegradable material by the fungi metabolism can also generate heat, little external thermal energy is normally needed to keep the intended temperature. However, depending on the production/system design either artificial heating or cooling may be used, either alone or both in alternation. The air transporting layer and/or the substrate layer, e.g. the incubation stack, may also be disinfected or sterilised, e.g. pasteurised, prior to inoculation or after soaking in water, although it is preferred that both layers are disinfected or sterilised. Any method of disinfection or sterilisation may be used in the present context. For example, heat may be used for disinfection or sterilisation, and in this case, the disinfection or sterilisation is generally referred to as "pasteurisation". Disinfection or sterilisation may be obtained using any available method, and the disinfection or sterilisation may be performed before, during or after wetting. For example, the air transporting layer and/or the substrate layer may be heated to a pasteurising temperature, e.g. in the range of 55°C to 120°C, for a pasteurising duration, e.g. of at least 20 minutes, e.g. at least 30 minutes, at least 60 minutes or at least 90 minutes. Alternatively, the air transporting layer and/or the substrate layer may be pasteurised using other methods, such as hot steam or radiation, e.g. with UV light of a shorter wavelength, or using high pressure autoclaving.

At least one of the air transporting layer and the substrate layer is inoculated with a wood-decaying fungus. In the present context, the inoculation starts a fermentation, and the respective layer may be referred to as a fermented layer or to an inoculated layer. The inoculation is performed using an inoculum, and the inoculum may have any form as desired. It is preferred that the inoculum is liquid, e.g. the inoculum may be a suspension of fungal spores, or the inoculum may be a suspension of fungal mycelium. A suspension of fungal mycelium may be obtained by mixing a lignocellulosic material that has been pre-inoculated with mycelium and used as a carrier to transfer the mycelium to a growing substrate. It is preferred that the air transporting layer and/or the substrate layer is inoculated prior to arranging the layers in the incubation stack. By inoculating the air transporting layer and/or the substrate layer with an inoculum e.g. a liquid inoculum, the wood-decaying fungus in the inoculum can be evenly distributed in the layer(s), and the even distribution ensures that the wood-decaying fungus is allowed to form a mycelium and to grow and decay the lignocellulosic material in the substrate layer(s) and in the air transporting layer(s). Any wood-decaying fungus may be used in the method, especially a basidiomycete. For example, the method may be performed with a white-rot basidiomycete fungus specie selected from the group consisting of Ganoderma lucidum, Ganoderma spp., Ganoderma resinaceum Pleurotus ostreatus, Trametes multicolor, Trametes versicolor, Trametes spp., Trametes hirsute, Fames fomentarius, Pycnoporus sanguineus, Lentinula edodes, Lentinus velutinus, , Schizophyllum commune, Irpex lacteus and Pleurotus albidus. An especially preferred wood-decaying fungus is Ganoderma Lucidum.

The inoculum may be a liquid suspension of the fungal mycelium or spores, e.g. a suspension of fungal mycelium in an aqueous liquid. When pasteurisation is used, the inoculum is added after the pasteurisation, but the inoculum, e.g. a liquid suspension of the fungal spores, may be added to at least one, e.g. all, of the air transporting layer(s) and the substrate layer(s) prior to forming the incubation stack, or the inoculum may be added to the incubation stack. In an example, the soaked layer(s) is/are drained after soaking, the layer(s) is/are pasteurised, and the inoculum is added to the drained layers. The amount of fungal mycelium in the inoculum can be selected based on the weight, e.g. the wet weight, of the mycelium relative to the wet weight, e.g. the drained wet weight, of the lignocellulosic material, including the hollow plant stems, of the layer to which the inoculum is added. For example, the inoculum may contain 2 w/w%, e.g. 3 w/w% to 10 w/w%, fungal mycelium, e.g. G. lucidum, relative to the wet weight of the layer or the incubation stack.

In an embodiment the hollow plant stem is reed. Reed is a common name for several tall, grass-like plants of wetlands and have a wide range of varieties, common reed (Phragmites australis), Giant feed (Arundo donax), Burma reed (Neyraudia reynaudiana), reed carnary-grass (Phalaris arundinacea), reed sweetgrass (Glyceria maxima), and Small-reed (Calamagrostis species). Reeds have a slender shape often with prominently jointed stems, where the stem has a hollow centre. The average diameter of the reeds stems is typically in the range of 0.5 cm to 1.5 cm and a reed can be up to 4 m in height. The height, diameter and the robustness of reed makes it a commonly used material for constructions e.g. thatching roofs. An advantage of the hollow plant stem is that it may function as a transportation channel, e.g. an air (or gas) transportation channel and/or a heat (energy) transportation channel, wherein it is possible to allow the movement of e.g. O2 and CO2. Therefore, the plurality of hollow plant stems allows for a surface area, and also a volume, in which the adjacent material gets access to gas exchange. When reeds are used as the hollow plant stems, the reeds may be arranged to be substantially parallel, e.g. in the XY plane, in the air transporting layer. The reeds may be arranged at a distance to each other in the range of 0 cm, e.g. the reeds abut neighbouring reeds, to 15 cm, e.g. 5 cm, with lignocellulosic material between the reeds. An air transporting layer made with reeds may contain a single layer of reeds, in particular neighbouring reeds, or several reeds stacked, e.g. in the Z dimension. In a specific example, the incubation stack comprises several air transporting layers made with reeds, and the air transporting layers may have the same or different thicknesses.

In another example, the hollow plant stem is a cereal straw, e.g. wheat straw. Wheat straw is generally more easily available than e.g. reeds, so that a cheaper manufacturing process is provided. Moreover, the cereal straws are more flexible than reeds, and thereby the air transporting layer can be shaped more easily to allow the composite material to be produced on a scaffold having a non-planar shape.

In a specific example, the incubation stack comprises one or more air transporting layers where the hollow plant stems are a mixture of reeds and cereal straw.

To optimise the flow of gasses to the surrounding substrate layer(s), it is beneficial to have plant stems that are hollow, and especially also stable, throughout the length of the hollow plant stems, although plant stems that are not hollow throughout the length of the hollow plant stems, e.g. bamboo, may also be used. Since the bamboo is not hollow all the way through, the bamboo stems may, in an alternative embodiment, be cut in half or otherwise modified, thereby creating a system of tunnels or air channels which may be able to exchange gasses to the surrounding environment, hence the substrate layer(s).

As previously mentioned, lignocellulosic material is generally referred to as a substrate for wood-decaying fungi. By providing a lignocellulosic material and arranging the lignocellulosic material in at least one substrate layer, the wooddecaying fungus is allowed to form hyphae and create a mycelium, e.g. a mycelium network, through and around the lignocellulosic material used for the substrate layer and also through and around the hollow plant stems of the air transporting layer. The substrate layer may use a variety of different lignocellulosic material. In an embodiment, the lignocellulosic material may be e.g. hemp hurds, wood chips, straw or reed, e.g. disrupted to a particulate form. The lignocellulosic material may be in the form of particles, e.g. particles having dimensions in the range of 1 mm to 5 cm. The particles may have any shape, but it is preferred that the particles have a shape to maximise the specific surface area of the particles, e.g. the particles may have a length, a width and a thickness, and the length may be 2 to 10 times, e.g. 5 to 10 times, or more longer than the width and/or the thickness. The lignocellulosic material may be from a single plant origin, or the lignocellulosic material may be from multiple different plants, e.g. the lignocellulosic material may be a mixture of hemp hurds, wood chips, straw, reed and other plant materials.

The lignocellulosic material may be selected together with a specific wooddecaying fungus to obtain a match between the wood-decaying fungus and the lignocellulosic material in order to obtain optimal growth conditions for the wooddecaying fungus. For example, the wood-decaying fungus may be G. lucidum, and the lignocellulosic material may contain particles of hardwood, e.g. the lignocellulosic material may comprise hardwood particles in the range of 10 w/w% to 50 w/w% of the lignocellulosic material, e.g. of the total weight of the lignocellulosic material.

The incubation stack may have a thickness, e.g. in the Z dimension, of at least 1 cm, preferably in the range of 1 cm to 1000 cm, e.g. 2 cm to 400 cm, e.g. 5 cm to 20 cm. The dimensions of the layers in the XY plane are generally defined by the desired product geometry, however, the dimensions of the layers in the XY plane may also be defined by the length of the hollow plant stems used in the air transporting layer. In an embodiment, the dimensions of the layers, e.g. in the XY plane, may be up to 10 m, e.g. in in the range of 0.5 m to 4 m, or in the range of 2 m to 2.5 m. The air transporting layer or the substrate layer may be shaped during the method of the disclosure. The step of shaping air transporting layer or the substrate layer may be done at any time during the method. For example, the air transporting layer or the substrate layer may be shaped before being inoculated with a wooddecaying fungus or after being inoculated with a wood-decaying fungus. When the shaping is performed after inoculating the air transporting layer or the substrate layer with a wood-decaying fungus, the shaping may be done during the fermentation or when the fermentation has been terminated. Prior to inoculating the air transporting layer or the substrate layer with the wood-decaying fungus, the incubation stack may be shaped. The shaping may involve cutting the incubation stack into discrete elements or applying the air transporting layer and the substrate layer to a surface having an intended shape.

After inoculating the air transporting layer(s) and/or the substrate layer(s) with the wood-decaying fungus, the wood-decaying fungus is allowed to grow and thereby form a mycelium, especially a mycelium network, across at least one interfacing surfaces to form the composite material. For the growth of the wooddecaying fungus, the plurality of the hollow plant stems, arranged in at least one air transporting layer, allows the growing wood-decaying fungal mycelium to exchange gasses, e.g. oxygen and CO2, and also heat energy, via the hollow plant stems of the air transporting layer(s), and further providing a balance of at least one of moisture, gas and temperature, dispersed transversely across the layer, especially the substrate layer or the lignocellulosic layer.

The substrate layer(s) and the air transporting layer(s) are alternatingly stacked, in which the air transporting layer(s) is enclosed in the substrate layer(s). In an embodiment the alternating stacking of the air transporting layer(s) with the substrate layer(s) forms an incubation stack comprising interfacing surfaces between the hollow plant stems and the lignocellulosic material, e.g. between the air transporting layers and the substrate layers. In an embodiment the layers may be stacked in any order of the substrate layer or air transporting layer and the number of substrate layers or air transporting layers is not limited to one substrate layer then one air transporting layer in the stack, but may be arranged with two substrate layers followed by three air transporting layers, etc. Correspondingly, the layers, whether the substrate layers or air transporting layers, need not have the same thickness. The respective materials in the layers may be ordered or arranged at random, especially with respect to the thickness of the respective layers.

The ability of the wood-decaying fungal mycelium to grow across the substrate and extend across the interfacing surface is affected by the ability of the air transporting layer(s) to transfer gasses, and also heat energy. This ability is influenced by the hollow plant stems used, the thickness, e.g. in the Z dimension, of the air transporting layer(s). The growth conditions during incubation, especially the duration of the growth, may be selected based on the hollow plant stems used, the wood-decaying fungus and the substrate, e.g. the lignocellulosic material, employed. During the incubation period, the wood-decaying fungal mycelium grows through and around the fibres of the lignocellulosic material, including the hollow plant stems, and binds them as to form a composite material. In general, the growth of the wood-decaying fungal mycelium may eventually decay the hollow plant stems to a degree so that the hollow plant stems collapse and form a solid material, or the hollow plant stems can collapse and form air pockets. It is contemplated within the present method that the growth of the wood-decaying fungal mycelium can be controlled to also control the collapse of the biodegradable material, e.g. lignocellulosic material or other materials, and thereby formation of air pockets can also be controlled. In an example, air pockets are especially desirable as they allow formation of a strong and light composite material. Formation of air pockets can especially be controlled when the composite material is shaped between two surfaces. When the hollow plant stems have been at least partly decayed, and collapse, the hollow plant stems leave residual material that is detectable in the composite material formed in the method. Thereby, the interfacing surface can be detected in the composite material and the degradation of the hollow plant stems allows for the composite material to be defined in terms of layers. Thus, the composite material comprises a mycelium of a wood-decaying fungus and at least one layer derived from a lignocellulosic material and at least one layer derived from hollow plant stems and an interfacing surface between the hollow plant stems and the lignocellulosic material, e.g. between a layer derived from a lignocellulosic material and a layer derived from hollow plant stems, wherein the mycelium transgresses the interfacing surface. The layer derived from a lignocellulosic material thus corresponds to the substrate layer of the present method, and the layer derived from hollow plant stems corresponds to the air transporting layer of the present method. However, due to the growth of the wood-decaying fungus in the incubation stack, the thicknesses of the layers in the composite material typically deviate from the thicknesses of the corresponding layers used in the present method.

The incubation period influences the rate of decay and thus the binding of the lignocellulosic material. The incubation period may be selected freely, although the incubation period may be selected according to desired composite material characteristics. It generally takes at least 2 days, e.g. at least 7 days, or at least 14 days, for the mycelium to transgress the interfacing surfaces to form the composite material. In an example, the incubation period is in the range of 14 days to 42 days. In general, the growth is stopped once the selected incubation period has been reached.

After the incubation, the provided composite material may be subjected to further processing steps to modify the shape of the composite material, and also the amount of air pockets in the composite material. The further processing steps may involve cutting the composite material, e.g. into discrete pieces of composite material having an intended shape, or further processing steps may involve joining separate pieces of the composite material, e.g. separate pieces of the stack, e.g. the composite material or composite material stack, obtained by cutting the composite material. Pieces of the composite material may be joined by curing or heat pressing two or more separate pieces of the composite material. The further processing steps may also involve dehydrating the composite material. Alternatively, the further processing steps may also involve heat-pressing the composite material, e.g. pieces of the composite material may be pressed together, or the composite material may be heat-pressed alone, e.g. without being in contact with further pieces of the composite material. Following the incubation period, two further steps, e.g. successive steps, may be included in the method to produce the final composite material. The two steps include heating to a set temperature to kill the wood-decaying fungus and dehydrating the composite material. Both approaches may also include shaping the composite material. The growth may be terminated first, or the shaping may be performed first.

The growth may be terminated by increasing the temperature in the incubation stack to kill the wood-decaying fungus. Thus, the growth may be terminated by heating to a temperature of at least 55°C, especially for a prolonged period. Termination of the growth may also include dehydration, or dehydration may be performed after the termination step. By increasing the ambient temperature of at least 55°C for a prolonged period, the wood degrading fungal mycelium is killed, and once heated to at least 55°C, the wood-decaying fungus will be killed, e.g. by using a terminating duration of at least 30 minutes, e.g. in the range of 60 minutes to 120 minutes, but the composite material will still, at least to some extent, be hydrated. Dehydration may be obtained by maintaining the temperature at at least 55°C, or by exchanging air around the composite material, e.g. by convective air drying or vacuum drying, or a combination of the two. The dehydration generally makes the mycelium stiff, achieves low-density, and stop the growth of the fungal mycelium but also avoid growth of other invasive microorganisms, such as mould. After dehydration, the incubated stack may be cut and segregated into discrete elements of desired geometric size and shape. As an example, the incubated stack is cut into discrete pieces using a band saw or a robotic wire cutter. After cutting, the elements may be sanded, and surface treated using oils or similar.

In the second approach, the incubation stack is cut into discrete elements of desired size and shape after which the elements are placed on a temporary shaping device, or shuttering, or flat shelf and are either dehydrated, cured or heat- pressed. During dehydration the elements stiffen into a new permanent shape. As an example, the elements can constitute the building envelope of a dome using discrete 3D-printed shaping devices, shuttering or moulds. Instead of dehydration, heat-pressing of the composite material can be used to produce a hard board of a 2 to 10 fold higher density which is either planer or non-planar. This method comprises the step of heat-pressing the composite material at a temperature in the range of 100°C to 200°C, e.g. 150°C to 200°C, for at least 15 minutes. The heatpressing removes water and kills the wood-decaying fungus.

Moreover a "curing" process can be included prior to dehydration. In this step discrete elements may be placed adjacently through which the fungal mycelium will leap across and transgress the elements, binding them together. In an example a fungal mycelium composite foam is placed on a heat-pressed mycelium composite board of higher density, e.g. of 6-fold increased density, in turn a 2-layer composite material constituting a multilayer product of e.g. insulation providing an inner hard surface. Moreover, this process may facilitate the growth of a protective and coloured fungal skin, on either discrete or bound elements, on the surfaces that are facing toward the ambient moist environment. This process may take at least 2 days and should be facilitated in a sterile environment and controlled microclimate. This environment may for example be similar to one provided in the chamber for the incubation stack, and optionally with an increased moisture content (CO2 5%, relative humidity of 100%).

Alternatively, a heat-pressing step may be added prior to dehydration with or without curing. In this step, the surface is heat-pressed at at least 100°C, e.g. at least 150°C, for at least 5 minutes and the surface is thereby smoothened thus promoting aesthetics and reducing surface area thereby decreasing risks of invasion by microorganisms such as mould.

In an embodiment, the method comprises the step of heating, e.g. heatpressing the composite material, at a temperature in the range of 55°C to 200°C, e.g. 100°C to 200°C, or 150°C to 200°C. Heating, e.g. heat-pressing is preferably performed before dehydration, and the heating, e.g. heat-pressing, or pressing may be combined with the termination of the growth of the wood-decaying fungus. In an example, the composite material produced in the method is pressed, e.g. heat- pressed, at a temperature in the range of 55°C to 200°C, e.g. 100°C to 200°C, or 150°C to 200°C, and this pressing or heat-pressing also terminates the growth of the wood-decaying fungus, and the combined pressing or heat-pressing/termination is then followed by dehydrating the composite material. In general, the pressing or heat-pressing increases the density of the composite material. For example, the pressing or heat-pressing can increase the density of the composite material at least 2 fold, such as at least 3 fold, at least 4 fold, at least 5 fold, or at least 6 fold.

In general, the method is performed by placing the incubation stack in an appropriate chamber. In general, the chamber is configured to allow for control of the micro-climate conditions within the chamber, e.g. the temperature, the composition of the air in the chamber, e.g. with respect to levels of humidity, CO2, and oxygen (O2) and other parameters. For example, a closed vapour proof and sterile housing encloses the incubation stack and creates a gas and water vapour buffer zone around the layers, where the microclimate can be controlled by predefined values of CO2, oxygen, humidity, and temperature. These values are selected to optimise the growth conditions of the selected wood-decaying fungus. The optimisation of the growth condition may be done actively or passively.

In the present context, active optimisation of the growth conditions of the wood-decaying fungus may include that the microclimate in the chamber or housing is maintained by conditioning of recirculated air. The air is forced via a ventilator through airducts and a conditioning unit outside the chamber or housing, which may humidify and/or dehumidify the air, adjust temperature and also the CCh-content and/or the oxygen (O2) content of the air, e.g. the oxygen (O2) content and/or the CO2-content may be decreased and/or increased. The air recirculation is designed such that the air is forced through the air transporting layers and thereby contributing to optimising the growth conditions within the layers. The active optimization does not require a predefined temperature in the surrounding environment.

In the present context, passive optimisation of the growth conditions of the wood-decaying fungus may include exchange of air, e.g. CO2 and/or oxygen, through a microfilter, e.g. placed on the walls of the chamber, which allows for gas exchange to the surrounding environment while filtering away airborne fungal spores and bacteria and maintaining humidity levels, thereby maintaining purity and high humidity in the housing. The microfilter used for the passive optimisation may be any microfilter with such attributes, e.g. a filter known as a SacO2 filter. The size of the filter, e.g. its surface area, may be selected based on the amount of substrate in the chamber or housing to maintain contents of CO2 and/or O2 at a useful level, e.g. CO2 of up to about 5%, e.g. >1.5%, which is produced by the fungal mycelium. The humidity level may thereby be maintained in the housing at approximately 99%. In the chamber or housing, or optionally also the surrounding environment around the housing, a predefined temperature of e.g. approximately 25°C to 30°C is maintained, depending on the fungal strains utilised.

In an example of the invention, the layers, i.e. the air transporting layer(s) and the substrate layer(s), are placed on a growth surface, e.g. a growth surface of the chamber or housing, before incubation. The growth surface may have any shape as desired. For example, the growth surface may be planar, or the growth surface may deviate from planar. In a specific example, the growth surface has a double curved shape reflecting the intended shape of the composite material produced in the method. The growth surface may be the surface of a scaffold or a scaffold assembly. In an example, the air transporting layer(s) and the substrate layer(s) are placed between two surfaces to thereby shape the air transporting layer(s) and the substrate layer(s), e.g. the incubation stack or the composite material, according to the respective surfaces and the spaces between the respective surfaces. It is also contemplated to use more than two surfaces, e.g. a growth surface and a surface of a counter scaffold and any number of further surfaces. For example, the method may employ a scaffold and two or more counter scaffolds. For example, the surfaces may include the growth surface of the scaffold and a surface of a counter scaffold. Together, the scaffold and the counter scaffold provide the material between the surfaces of the scaffold and the counter scaffold with the corresponding shape. In the present context, the fermentation of a material on a surface is considered "shaping" the material. In a specific example, the growth surface is placed on a scaffold of a material that is removable from the housing, and which is further removable from the composite material after the production of the composite material. Thus, the method may comprise the step of removing the composite material, e.g. the shaped composite material, from the scaffold. For example, the scaffold may be made of a material not comprising lignocellulosic material to thereby prevent the mycelium to grow into the scaffold material. The scaffold may for example be a polymer or clay. It is also contemplated that when a scaffold is used, especially a scaffold that is removable after the incubation, the method is used without the air transporting layer, e.g. no hollow plant stems are used.

Various details of the features of the present invention are illustrated in Figure 5. For example, Figure 5 shows the layers and the incubation stack at different stages of the method, and the composite product is also shown.

A second aspect of the invention is a composite material comprising a mycelium of a wood-decaying fungus and at least one layer derived from a lignocellulosic material and at least one layer derived from hollow plant stems and an interfacing surface between the hollow plant stems and the lignocellulosic material, wherein the mycelium transgresses the interfacing surface. The composite material is obtainable in the method of the invention, and any embodiment of the method may be used to produce the composite material, and any advantage explained for any aspect of the invention is equally relevant for the other aspect of the invention.

Additionally, variations to the disclosed embodiments may be under-stood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.

Brief description of the drawing

The present invention will now be described in more detail with reference to the appended schematic drawing showing embodiment(s) of the invention.

Figure 1 schematically shows the incubation stack of the invention;

Figure 2 schematically shows a chamber with incubation stack of the invention;

Figure 3 schematically shows a chamber with incubation stack of the invention;

Figure 4 schematically shows a chamber with incubation stack of the invention;

Figure 5 shows various details about the invention;

Figure 6 shows various details about the invention.

Detailed description

In the figures, the sizes of components and regions may be exaggerated for illustrative purposes and, thus, are intended to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout, even though they may not be identical.

Referring initially to Figure 1, reeds were provided from a lakeshore in Denmark as the hollow plant stems 21. The reeds were of the species common reed Phragmites australis and each reed had a length of about 2 m and a diameter of 5 mm to 8 mm. The reeds were placed side by side in a layer to make up the air transporting layer 2. Hemp hurds were provided from a local Danish producer and used as the lignocellulosic material 31. The hemp hurds were fibrous particles with a length of 0,1 to 1,5 cm, and the hemp hurds were placed on the transporting layer 3. Thereby, an interfacing surface 32 was created between the reeds and the hemp hurds, e.g. between surface of the reeds and surface the hemp hurds. Further layers of reeds and hemp hurds were added to provide an incubating stack 4 containing four layers of hemp hurds, i.e. four substrate layers 3, and three layers of reeds, i.e. three air transporting layers 2. However, more layers, i.e. air transporting layers 2 followed by substrate layers 3 each arranged alternatingly may be arranged at the arrow. Prior to stacking, each layer 2,3 was pasteurized, soaked in water, then drained, and an inoculum of Ganoderma lucidum was added to the layers. The inoculum was provided by growing mycelium of G. lucidum at 26°C on grain for five days thereby providing a mycelium carrier appropriate for transferring the mycelium to the growing layers. In another example, Trametes versicolor was used for inoculation.

The layers 2,3 were stacked, and the incubating stack 4 was placed in an enclosed chamber 7 where the temperature and also the microclimate could be controlled, and air access was provided through a filter with a 0.45 pm pore size. Specifically, the microclimate was controlled to have 99% relative humidity (RF) and 5% CO2. The temperature was maintained between 25°C and 30°C, and the incubation stack 4 was incubated for 21 days. The incubation allowed formation of the mycelium in the incubation stack 4 and the mycelium transgressed the interfacing surfaces 32 thereby providing the composite material 1.

In a sterile environment the incubation stack 4 was cut to discrete planar elements that were placed in adjacency on a continuous non-planar scaffold 5. In a micro-climate-controlled environment, the discrete elements were cured, and grown together, and formed an outer fungal skin. The curing of the joined elements were then terminated by increasing the temperature to 55°C and by dehydration for 7 days. In an alternative example, a temperature of 60°C was used. The scaffolds were removed leaving behind a self-supporting, stiff, low-density, insulating, sound absorbing composite material structure.

Further embodiments are shown in Figure 2, Figure 3, and Figure 4 where the incubation stack 4 is shown in a chamber 7. These Figures show a left panel where the incubation stack 4 is depicted in an XZ or YZ plane and a right panel where the incubation stack 4 is depicted in perspective. The elements of the incubation stack 4 are as shown in Figure 1, and in Figure 2, the air transporting layers 2 and the lignocellulosic substrate layers 3 are ordered. Specifically, the hollow plant stems 21 are arranged in parallel in a discrete layer to form the air transporting layers 2. In Figure 3, the hollow plant stems 21 are arranged in parallel but without forming a distinct layer in the XY plane. In Figure 4, the hollow plant stems 21 are arranged in random but in a distinct layer.

Further details are illustrated in Figure 5, which in panel A shows incubation of combined air transporting layers 2 and lignocellulosic substrate layers 3. Panel A also shows the hollow plant stems 21 and the lignocellulosic material 31 placed in a chamber 7. Panel B shows the composite material 1, e.g. as an incubation stack 4, as a generic living mass. In panel C, the incubation stack 4 is dehydrated and heated. Panel D shows how the composite material 1 has been cut into discrete, dehydrated elements 11. Panel E shows three subpanels with the incubation stack 4 where the air transporting layers 2 and the lignocellulosic substrate layers 3 are incubated (left subpanel) and how, during incubation, the fungal mycelium 33 grows across the air transporting layer 2 and lignocellulosic substrate layer 3 and transgressing the intersecting layer at the interfacing surface 32 (encircled middle panel). In the right panel of panel E, the composite material 1 is shown as a growing living mass during incubation. In panel G, the composite material 1 has been cut as discrete living elements 11, and in panel H, the discrete elements 11 are shown after dehydration on the growth surface 51 of a scaffold 5, where the discrete elements 11 are grown together on the scaffold 5.

Figure 6 shows details about steps in the method with reference to the incubating stack 4 containing substrate layers 3 with lignocellulosic material 31 and air transporting layers 2 with hollow plant stems 21 as explained above for the other figures. Thus, the layers 2,3 are stacked and inoculated with fungi before incubating in step SI. Step S2 includes heat-inactivation and drying of the composite material 1 before cutting the composite material 1 in step S3. This involves obtained multiple and various shapes after cutting. As an alternative, the fermented incubating stack 4 is cut into desired shapes in step S4, and the following step S5 generally involves variations of the heating step. Thus, in step S5-1, the pieces are shaped on a scaffold 5 and heated to provide form dehydration and heat-inactivation. In step S5-2, the cut pieces are positioned adjacent before a combined drying and heat-inactivation to join the pieces to a single piece. In step S5-3, the cut pieces are heat-pressed and heat-inactivated.

Reference numerals

1 Composite material

11 Discrete element

2 Air transporting layer

21 Hollow biodegradable members 3 Substrate layer

31 Lignocellulosic material

32 Interfacing surface

33 Fungal mycelium 4 Incubation stack

5 Scaffold

51 Growth surface

6 Counter scaffold

7 Chamber

Claims

P A T E N T C L A I M S

1. A method of producing a composite material (1), the method comprising the steps of:

- providing a plurality of hollow biodegradable members (21) and arranging the hollow biodegradable members (21) in at least one air transporting layer (2);

- providing a lignocellulosic material (31) and arranging the lignocellulosic material (31) in at least one substrate layer (3);

- wetting at least one of the air transporting layer (2) and the substrate layer (3) with water;

- alternatingly stacking the air transporting layer(s) (2) with the substrate layer(s) (3) to form an incubation stack, the incubation stack (4) comprising interfacing surfaces (32) between the hollow biodegradable members (21) and the lignocellulosic material;

- inoculating at least one of the air transporting layer (2) and the substrate layer (3) with a wood-decaying fungus;

- allowing the wood-decaying fungus to form a mycelium (33) across at least one interfacing surfaces (32) to form the composite material (1).

2. The method according to claim 1, wherein the hollow biodegradable members (21) are hollow plant stems.

3. The method according to claim 1 or 2 further comprising the step of heating the composite material (1) to a temperature in the range of 50°C to 200°C.

4. The method according to claim 3, wherein the heating comprises heat-pressing.

5. The method according to any one of claims 1 to 4 further comprising the step of shaping the incubation stack (4) prior to or after inoculating the air transporting layer (2) or the substrate layer (3) with the wood-decaying fungus.

6. The method according to claim 5, wherein the air transporting layer(s) (2) and the substrate layer(s) (3) are placed on a growth surface (51) of a scaffold, and the method further comprises the step of removing the composite material (1) from the scaffold (5).

7. The method according to claim 6, wherein the air transporting layer(s) (2) and the substrate layer(s) (3) are placed between the growth surface (51) of the scaffold (5) and a surface of a counter scaffold (6).

8. The method according to any one of claims 1 to 7, wherein the lignocellulosic material 31 comprises material from two or more sources.

9. The method according to claim 8, wherein the lignocellulosic material 31 comprises material a wood-derived material and a hemp-derived material.

10. A composite material (1) comprising a mycelium (33) of a wooddecaying fungus and at least one layer derived from a lignocellulosic material (31) and at least one layer derived from hollow biodegradable members (21) and an interfacing surface (32) between the hollow biodegradable members (21) and the lignocellulosic material, wherein the mycelium (33) transgresses the interfacing surface.

11. The composite material (1) according to claim 10, wherein the composite material (1) has a thickness of at least 2 cm.