Production and Testing of Moisture Behavior and Thermal Properties of Rapeseed Straw and Ganoderma resinaceum Mycelium Bio-Composites

Our research aims to integrate mycelium biocomposites into the construction industry by developing materials that are competitive with the current conventional options. We address performance, durability, and applicability. The protocol addresses the gap in ensuring correct production and testing of mycelium biocomposites in alignment with the construction industry standards, with a focus on achieving repeatable and homogenous experimental results.

The material shows performance comparable to conventional construction materials, especially in terms of insulation, highlighting its promise. The next challenge is addressing durability and end-of-life management. The latter, a novel consideration for bio-based construction materials.

Our focus will remain on mycelium construction materials, and in the future, also focus on pure mycelium materials, looking at the intrinsic values of fungal species, as well as in mycelium biocomposites. We also look into automation for the industrial scape. To begin, use a sterile inoculation loop to cut a fully colonized 100 millimeter diameter Petri dish of ganoderma resinaceum medium into four equal sections.

Transfer two sections of the colonized medium to a sterile laboratory blender cup. Add 50 milliliters of malt extract broth to the cup and mix it with the mycelium on agar. Then pour the inoculated broth mixture into the bag containing autoclave, cellulose and water.

Massage the contents of the bag manually for two minutes to ensure even mixing. Now set the climate chamber to 30 degrees Celsius and 80%relative humidity, and transfer the inoculated bag to the climate chamber for five days. For substrate preparation, place an empty bowl or bucket on a scale and tare it.

Then transfer the substrate into the bucket and record its weight. Next, weigh demineralized water in a 1.65 to one ratio relative to the substrate. Mix the substrate and water thoroughly with the hands.

Use a cement mixer for handling larger quantities of substrate. Then place the hydrated substrate mixture into autoclavable bags. Place the bags in an autoclave, and run a cycle at 121 degrees Celsius for 25 minutes.

For substrate inoculation, using a scale, weigh the spawn to be 10%of the total wet weight of the substrate and water. Pour the weighed spawn into the bag containing the sterilized substrate. Then seal the bag using a heat sealer or tape, and shake or massage the bag gently for two minutes to distribute the spawn evenly.

For molding, weigh the mold on the scale. Fill it with the inoculated substrate, and spread it evenly to create a flat surface. Afterward, cover the mold with perforated foil and secure it in place with tape.

Place the filled and covered molds in a climate chamber set to 25 degrees Celsius and 80%relative humidity for seven days. After approximately seven days of growth, carefully remove the sample from the mold. Place it on baking paper in an oven set to 65 degrees Celsius for 24 hours to absorb moisture and prevent sticking.

After calibrating the heat flow meter software, input the basic data and specimen description into the software. Set the upper and lower plate temperature as required. Then place the mycelium-based composite sample in the heat flow meter, and close the door.

Select the previously performed calibration. Then left-click to tick the load set point at 2.1 kilopascal, and click the start button to initiate the test. To measure specific heat capacity, place the mycelium-based composite sample inside the heat flow meter, and close the door securely.

Set the values specified in the set point table. And select the previously performed empty stack calibration. Left-click to tick the load set point at 2.1 kilopascal.

Then click the start button. For moisture absorption and desorption analysis, prepare a water box filled to one quarter of its height with water. Use three strips of plastic tape to suspend the mycelium-based composite sample above the water without touching it.

Then measure the sample using a vernier caliper. At specified intervals of zero, 0.5, 1, 2, 4, 8, 24, and 48 hours, remove the sample from the water box. Weigh it on a scale, and measure its dimensions quickly to minimize moisture loss.

After each measurement, return the sample to the water box and close the lid. After 48 hours, take the sample out of the water box, and place it in a climate chamber set at 25 degrees Celsius and 40%relative humidity. For compressive strength measurements, use a vernier caliper to measure the dimensions of the mycelium-based composite sample following standard procedure.

Place the sample in the universal testing machine, positioning it centered above the lower compression plate. Then turn on the universal testing machine, and start the operating software to ensure proper connection. In the software, search for ISO 29469 using the search tool.

Right-click the listed standard, and press Edit Method to proceed. Press the Start Experiment button in the universal testing machine software to start the compression test. To condition fresh samples, suspend them in the water box for 24 hours as previously described.

Transfer unused humid samples to an oven set to 50 degrees Celsius with fan ventilation for 12 hours. To assess water repellents, add nine milliliters of water with one milliliter of blue dye in a 20 milliliter Erlenmeyer, and mix thoroughly. Then using a thin felt-tip pen, divide the surface of the mycelium-based composite sample into four quadrants.

Using a micropipette, measure 100 microliters of the dyed water. Place one droplet on a flat surface in each of the four quadrants. Using a tripod-held camera, aligned at eye level with the top surface of the sample, take a photograph of each droplet.

Samples that passed visual inspection showed a white uniform surface with smooth texture and no discoloration or flaking, matching the expected appearance for adequately grown mycelium-based composites. Visibly non-adequate mycelium-based composite samples exhibited signs of contamination, including multicolored surface patches such as green, black, yellow, and blue, as well as areas with uneven texture, and flaky or overgrown regions. A third example of poor quality MBC showed a loosely packed structure with visible straw particles and incomplete mycelium coverage.

The average thermal conductivity of the samples remained consistently low at 0.0367 watts per meter Kelvin, confirming adequate insulation properties. The average compressive strength was highest in the post-dried condition at 24.99 kilopascals, followed by the dry state at 21.02 kilopascals. And lowest under wet conditions at 14.85 kilopascals.