**Appendix I**

The evolution of mycelium and contaminant growth in the first batch is briefly described here. During the growth process, the state of the panels placed was visually assessed in a see-through enclosure. Environments were kept closed to limit contamination. Eleven days after inoculation, small amounts of mycelial growth were observed on the specimens. However, grey and green spots, likely contaminants, were seen. Twenty-one days after inoculation, mycelium formed a thin mat over most of the visible specimens' surfaces. The grey and green spots were still present. Forty-six days after inoculation, the mycelium formed a thick mat over the specimens, and the growth environments were opened for thorough assessment.

Further information about the height shrinkage and weight reduction of both cylindrical and rectangular specimen types is presented here. The shrinkage of the specimens grown for compression testing (i.e., in PVC pipes) was calculated by comparing the weight and dimensions of all specimens at the following stages: (1) inoculation, (2) beginning of drying (i.e., when growth environments were opened at the end of the growth period), (3) before cutting (i.e., specimens had to be cut to the sizes required for testing), (4) before the application of post-growth treatments, (5) before baking or drying, and (6) before mechanical testing (Table A1). To limit the growth of the contaminants after the mycelium growth period, contaminated parts of the specimens were removed from the grown materials. These parts do not possess mycelial growth. As such, they should not be used for the mechanical tests since they would generate invalid data. Removing these pieces jeopardized the comparison of the height and weight measurements. The width was not affected as the contaminated pieces were mostly slices at the top and bottom of the specimens. Therefore, upper or lower portions of the specimens were removed. In this regard, the weight evolution was analyzed for the specimens, with less than 10 g of contamination removed throughout the entire process.

**Table A1.** This table shows the evolution of the weight, height, and diameter from inoculation to the beginning of compression testing. Specimens were cut between steps 3 and 4. The weight was therefore kept between these two steps to ensure the comparison was continuous. The height was reset to 100% once the specimens were cut.


The weight and dimensions of all specimens grown for bending testing were measured at the following steps: (1) inoculation, (2) beginning of drying, (3) before the application of post-growth treatments, (5) before baking or drying, and (6) before cutting to required sizes for testing (Table A2). In contrast to cylindrical specimens, the post-growth treatments were applied to the specimens before cutting them to fit testing requirements for practicability. Each grown specimen was cut into six test specimens directly before the bending testing. All specimens grown for bending contained some contaminants. The weight of contamination manually removed during step 2 accounted for 28.84% of the initial weight of the specimens at inoculation. However, the uncontaminated parts of the specimens had to be trimmed further to fit the size requirements for testing. In total, 42.78% of the initial weight was

removed and could not be used for testing. Therefore, tracking the evolution of these measurements was more challenging. The data were divided into two sets to facilitate the analysis: all specimens, and only those on which less than 10% of contamination was removed throughout the entire process.

**Table A2.** This table shows the evolution of the weight, height, width, and length for the specimens grown for bending. Uncompacted (NC) and compacted (C) specimens were analyzed separately since compacted specimens were constrained in metal frames used for compaction.

