Abstract
Mycelium-bound composites are promising materials for sustainable packaging, insulation, fashion, and architecture. However, moulding is the main fabrication process explored to date, strongly limiting the ability to design the complex shapes that could widen the range of applications. Extrusion is a facile and low energy-cost process that has not yet been explored for mycelium-bound composites with design freedom and structural properties. In this study, we combine cheap, easily and commonly available agricultural waste materials, bamboo microfibres, chitosan, and mycelium from Ganodermalucidum, to establish a composite mixture that is workable, extrudable and buildable. We study the impact of bamboo fibre size, chitosan concentration, pH and weight ratio of bamboo to chitosan to determine the optimum growth condition for the mycelium as well as high mechanical stiffness. The resulting materials have thus low energy costs, are sustainable and can be shaped easily. The developed composition is promising to further explore the use of mycelium-bound materials for structural applications using agricultural waste.
Highlights
To prepare mycelium-enriched bamboo fibres to use in the composite paste to be extruded, mycelium is first grown on the fibres
It is known that the mycelium growth kinetics, morphology, and properties are largely influenced by the substrate that provides the physical support and nutrients to the fungus [41]
To determine which bamboo fibre size to use in our composition, we first incubated the mycelium-enriched sawdust with chopped bamboo fibres of 1 mm, 500 μm and 200 μm-length, and studied the mycelium morphology and properties (Fig. 3)
Summary
To be able to extrude mycelium-bound composites, it is necessary to develop an initial paste or mixture that is extrudable and has shaperetention properties In the following, these two characteristics are termed workability and buildability [27,28,29]. We explore the use of bamboo chopped fibres and chitosan as ingredients to increase the workability and buildability of mycelium mixtures to build mycelium-bound composites using extrusion. The bamboo fibres will provide the nutrients for the growth of mycelium [35,36], chitosan will serve as a rheological modifier to increase the workability and allow extrusion, and the mycelium will bind all the component together These components are natural and readily available from agricultural waste, making them interesting as sustainable alternative materials. Further optimisation of the substrate composition could enhance the final properties of the mycelium-bound material
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