Applicability of Paper and Pulp Industry Waste for Manufacturing Mycelium-Based Materials for Thermoacoustic Insulation

Abstract

Cellulose and paper produce significant waste such as ash, activated sludge, and sludge from the pulp and paper industry. Depending on the raw material, legislation, and subprocesses, these sludges contain around 30–50% organic matter, mainly composed of less than 0.02 mm cellulose fibers and hemicellulose and lignin. This work used sludge from the pulp and paper industry as a substrate for manufacturing mycelium-based biomaterials using the white rot fungus Trametes versicolor. Chemical and surface analyses revealed the formation of new materials. Acoustic impedance analyses revealed that these materials have a noise reduction coefficient and sound absorption average comparable to extruded polystyrene and polyurethane. In addition, the material’s thermal conductivity was near that of sheep wool. Therefore, the biomaterials fabricated using sludge and Trametes versicolor have the potential to be a game-changer in the industry as promising thermoacoustic insulators.

1. Introduction

Expanded polystyrene (EPS) is one of the most widely used thermal insulators in the construction and packaging industry. EPS-based materials are mainly preferred due to their low cost and versatility, for almost half of thermal. These materials represent 30% of insulator materials for the construction market in the European Union [1]. According to the life cycle assessment developed by Kulakovskaya in Switzerland, the economic and environmental impacts of EPS boards in 2020 were 662 million CHFs and 134 kilotons of CO₂-eq, respectively [2]; however, they have a low recycling rate. A 2018 study revealed that in 2014, of the 2.2 million tons of polystyrene produced in the United States, only 20,000 tons were recycled, representing a rate of just 0.9% [3]. This is why the pollution associated with this type of material is a growing environmental concern, not only due to the large amount of waste but also due to the adverse effects of its waste on ecosystems, such as the marine ecosystem and human health [4].

Developing new biodegradable materials that can replace petroleum-based materials while mitigating their environmental footprint represents a tremendous scientific and technological challenge. In this context, mycelium-based materials that use white rot fungi are a cutting-edge alternative to replace EPS in the construction industry. These materials are manufactured using specialized white rot fungi, which decompose wood or lignocellulosic waste [5], forming a white and spongy substance that can be used to produce affordable and environmentally sustainable biomaterials, as reported previously. For instance, Al-Qahtani et al. [6] reported a review on mycelium-based thermal insulation for domestic cooling footprint reduction. Volk et al. [7] studied the life cycle assessment of mycelium-based materials. Charpentier-Alfaro et al. [8] reported on decaying fungi for mycelium-based materials. Ghazvinian et al. [9] investigated the mycelium-based approach for architectural applications. Attias et al. [10] studied nanocellulose–mycelium materials. Teixeira et al. [11] analyzed the production of biodegradable mycelium-based materials and their mechanical properties using white rot fungi. Huang et al. reported that white rot fungi can degrade lignin and its derived structures, colonizing wood from living or dead trees through their intra and extracellular systems of oxidative enzymes [12]. Meanwhile, Harshvardhan et al. [13] proposed that these biomaterials can be promising tools for the biotransformation of endocrine-disrupting compounds.

Therefore, white rot fungi can colonize a substrate based on the hyphae bind. The particles that form the substrate act as an adhesive that holds a mycelial network. This characteristic and its ability to degrade lignin and cellulose make white rot fungi ideal for creating materials from lignocellulosic waste, such as those from the pulp industry. These biomaterials, known as mycelium-based materials (MBMs), possess properties that would allow them to be positioned as a replacement for traditional insulating and packaging materials due to their thermal conductivity, sound absorption, and fire safety properties, being similar to materials such as EPS, which are frequently used in this kind of application [14,15,16]. In addition, a 2022 study showed that thermal inertia allows the manufacturing of bricks that reduce temperature fluctuations in buildings compared with other materials, such as expanded vermiculite and lightweight expanded clay [17].

The addition of nano- and microcellulose has been widely researched to enhance the mechanical properties of fungal biomaterials. For instance, incorporating 30% cellulose nanofibers improves tensile strength by 30% and elasticity by 44% [10]. Bhagavathi et al. [18] reported that adding microcrystalline cellulose accelerated the curing process of polyurethane. Marcuello et al. [19] proposed that hemicellulose improves the interfacial adhesion properties of lignocellulosic polymers. Studies also show that mycelium foams grown on cellulose from wastewater treatment have compressive strengths comparable to expanded polystyrene (EPS) but with double the density [20]. Sayfutdinova and colleagues found that adding cellulose results in cohesive biomaterials, with microcellulose degrading in two weeks and nanocellulose in five days, promoting mycelium growth [21]. Bacterial cellulose improves particle cohesion and increases density and tensile strength, thus enhancing compressive strength [14,22]. Additionally, Sun et al. showed that adding 2.5% cellulose nanofibers to a wood particle substrate yields a biomaterial with improved flexural strength and elastic modulus [23]. These findings highlight the potential of cellulose additives to significantly enhance fungal biomaterials, paving the way for sustainable and high-performance materials.

The sludge generated as waste by the pulp industry, called pulp and paper mill sludge (PPMS), represents a valuable alternative for incorporating cellulose from these residues. Including micrometric cellulose could significantly improve the mechanical properties of the resulting biomaterials, especially in terms of compressive strength. This is partly because for each ton of paper, around 40 to 50 kg of dry solid waste is generated, of which 70% is primary sludge. It is worth noting that world paper production exceeded 400 million tons in 2020, and the generation of primary sludge far exceeds 12 million tons annually [24]. These residues, generated during the cellulose fiber liberation process, are primarily composed of short fibers of less than 0.2 mm, which are unsuitable for manufacturing cellulose products, as well as hemicellulose, lignin, and peptides hydrolyzed during the process (see Table 1) [25,26,27].

Building on these premises, this study verified the hypothesis that applying PPMS to fabric mycelium-based materials is suitable for thermoacoustic insulation in construction applications. In particular, MBM was manufactured using sludge from the pulp and paper industry. For this purpose, the white rot fungus Trametes versicolor was used, which has a high potential for producing this type of biomaterial [14,16,30,31]. The materials produced were characterized using physicochemical, morphological, microstructural, and acoustic analyses, compared with commercially available materials currently available as thermal and acoustic insulators. This way, its potential use in a sustainable construction industry was evaluated.

2. Materials and Methods

2.1. Materials

The PPMS was provided by a local pulp- and paper-processing mill as original waste. In particular, it was kept humid and stored in a plastic bag at room temperature for about two weeks. The solid agar medium was malt extract Agar (Merck, Rahway, NJ, USA) and agar-agar (Winkler Ltd., Santiago, Chile).

2.2. Physicochemical and Microstructural Characterization of Sludge

The pH of the received sludge was evaluated by suspending 5.0 g of dry sludge in 100 mL of distilled water. The humidity was determined by drying 100.0 g of the sludge at 105 °C for 24 h and calculating the difference in mass. The organic matter content was assessed by calcining 100.0 g of the sludge at 800 °C, with the weight of the remaining solid corresponding to ash and the mass loss representing organic matter. The sludge samples were analyzed in triplicate.

Chemical analysis of the sludge was carried out using attenuated total reflection infrared spectroscopy (Shimadzu IRSpirit FTIR, Japan) and atomic absorption spectroscopy (Perkin Elmer PinAAcle 900 Series AA). The crystalline phases in the sludge were analyzed by X-ray diffraction (Bruker D8 Advance, CuKα, Germany). To verify the presence of heavy metals in the sludge, inductively coupled plasma mass spectrometry (ICP-MS) was used (Perkin Elmer Elan 9000 ICP/MS, USA).

2.3. Preparation of Biomaterial

2.3.1. Fungal Inoculum

The spawn of Trametes versicolor was selected for its performance in biomass generation and hyphal extension, as described by Jones et al. [32]. This fungus is known for degrading lignin and cellulose at higher rates than other fungi, making it particularly suitable for the present study. Its proven ability to grow on Eucalyptus and pine trees, used in manufacturing cellulose pulp at the plant that provided the PPMS, further justified its use in this study. For this study, the spawn of Trametes versicolor AC9911 was sourced from Agrocontinental Chile S.A. and stored at 4 °C in a breathing bag.

2.3.2. Substrate Preparation

The pulp and paper mill sludge was dehydrated at 105 °C (ECOCELL 111, MMM group, Germany) for 24 h and stored dry in airtight vacuum bags. To be used as a substrate, the sludge was rehydrated with excess freshwater, blended for 2 min, and soaked overnight. The excess water was removed, and the sludge was sterilized in an autoclave (All America, 25X-2, USA) at 121 °C for 20 min using a polypropylene container. Figure 1 summarizes the substrate preparation carried out in this work.

2.3.3. Mycelium Cultivation and Deactivation

The biomaterials were manufactured by mixing 10 wt.% of Trametes versicolor with 90% of the substrate, which had been sterilized in an autoclave using molds. The molds were filled layer by layer, compressing and filling to achieve a 1.015 g/cm³ density. The prismatic molds used were 160 × 40 × 40 mm, designed in 3D using Thinkercad (http://www.tinkercad.com, accessed on 27 August 2024), and printed in PLA (Creality Ender-3 V2, eSUN 1.75 mm). They featured easy-release mechanisms and holes to facilitate gas exchange between the substrate and the atmosphere.

The samples were then incubated at 28 °C and 85% relative humidity (BIOBASE BJPX-M150) for 7 days inside the molds, followed by 3 days outside to allow the growth of a white mycelium covering. All samples were dried in a convection oven (ECOCELL 111) at 80 °C for 12 to 24 h until their weights stabilized, ensuring a low humidity unsuitable for further fungal development. The mycelium’s weight, diameter, and height were measured for each sample before and after drying. The percent shrinkage was calculated by subtracting the dry volume from the wet volume and then dividing this shrinkage by the wet volume. Figure 2 shows photographs of the mycelium-based material fabricated using Trametes versicolor on PMMS.

2.4. Hyphae Growth Rate

To measure the hyphal growth rate, malt extract agar (MEA) (48 g/L, Merck) and a solid medium composed of sludge from the pulp and paper industry and agar-agar (Winkler) (53 g of dry PMMS and 20 g of agar-agar in 1000 mL of distilled water) were used. The media were sterilized in an autoclave at 121 °C for 20 min. Molten agar was aseptically poured into 90 mm Petri dishes under a laminar flow hood and allowed to solidify. A single inoculum was placed at the edge of each Petri dish, contacting the wall of the dish. Each experiment was performed in triplicate. The plates were individually sealed with Parafilm and incubated at 28 °C and 85% relative humidity in the dark. The radial growth (mm) was measured daily from the center of the inoculum to the tip of the longest hypha at the same time each day for 11 days. The plates were photographed and processed with the ImageJ software (1.54i version) [33].

2.5. Characterization of MBM

The density of the biomaterials was evaluated following the ISO standard 9427:2003 [34], considering the biomaterial’s dry mass ratio to its volume. The moisture content was also determined based on ISO 16979:2003 [35]. The water absorption rate was also evaluaJapanted following the ASTM standard C 1585 [36].

The biomaterials were chemically analyzed by attenuated total reflectance spectroscopy (Shimadzu IR Spirit FTIR, Japan) at 24 °C with 40% relative humidity, averaging at 10 scans with a resolution of 1 cm⁻¹. Additionally, surface analysis of the biomaterials was performed using field-emission scanning electron microscopy (FE-SEM, Zeiss GeminiSEM 360, Germany) operated at an EHT of 5 keV, which also allowed for a relative chemical analysis using EDX (Oxford max ultra 40).

2.6. Thermal and Acoustic Analysis

The thermal conductivity of the biomaterials was analyzed using a KD-2 PRO thermal analyzer with the KS1 probe. Using the transient linear heat source or hot needle method, the KD2-Pro device was used for thermal analysis and complied with references [37,38]. In the traceability process of the thermal analyzer KD2-Pro with the KS-1 sensor, several thermal conductivity measurements were performed on glycerin (CAS 56-81-5), whose thermal conductivity was 0.282 W/mK at 20 °C.

The acoustic conductivity of the biomaterials was studied through an acoustic We added this reference to the reference section and modified the reference numbers impedance, according to references [39,40], using a sonometer located 5 cm from the tube entrance, and then a white noise signal was applied and adjusted to 90 Dba. The sound spectrum was also adjusted using an equalizer for 1/8 frequency bands between 63 Hz and 5000 Hz. Before the analysis, an initial test was conducted using an acoustic isolation foam sample with the exact dimensions of the studied samples. When the sound absorption measures were similar to those reported by the material supplier or in bibliographic references, each sample was analyzed. To verify the data consistency, every sample was registered up to 6 times for 5 s at 7 different microphone positions.

2.7. Data Analysis

In this work, the OriginPRO 2016 software, Version 93E (Origin Lab Corporation, Northampton, MA, USA) was used to process the raw data using different techniques.

3. Results and Discussion

3.1. Physicochemical Characterization of Sludge

Table 2 shows the main physicochemical properties of the sludge used for manufacturing the mycelium-based materials in this work.

Figure 3 shows the ATR FT-IR spectrum of the sludge and the main infrared transmittance bands of the chemical components of the sludge, where the presence of characteristic cellulose signals can be observed. In particular, the stretches characteristic of the O-H bond specific to cellulose are present between 3595 cm⁻¹ and 3865 cm⁻¹ (peaks 8, 9, 10, and 11). Also, the peaks between 2800 cm⁻¹ and 2937 cm⁻¹ (peaks 6 and 7) correspond to the asymmetric stretches of the C-H bonds of the aromatic and aliphatic groups found in cellulose, hemicellulose, and lignin. The presence of cellulose is further supported by the peaks at 1054 cm⁻¹ and 1030 cm⁻¹ (peaks 1 and 2), corresponding to the asymmetric stretches of the C-O-C bonds present in cellulose [41,42]. The transmittance band at 1684 cm⁻¹ (peaks 4 and 5) corresponds to the OH group likely associated with water absorbed in the sludge. Finally, peak 3 at 1512 cm⁻¹ is characteristic of calcium carbonate, which is used in the Kraft process of cellulose production [43,44].

Table 3 summarizes the contents of elements detected by ICP-MS. It reveals several heavy metal ions, such as Cd, V, and Hg, but their concentrations are insignificant. Therefore, manipulating the sludge in manufacturing mycelium-based materials would be safe for humans. Additionally, the high contents of calcium, sodium, and potassium ions and the absence or low concentration of toxic metals favor mycelial growth, indicating that the substrate is adequate.

Figure 4 shows the sludge’s X-ray diffraction patterns, revealing the presence of a crystalline cellulose phase [41,45], with diffraction peaks located at 2θ = 15.04°, 16.88°, and 22.74°, associated with the (1–10), (110), and (200) planes [46], highlighted in red. It has been reported that cellulose favors the development of mycelia, improving the mechanical resistance that allows them to spread and explore their environment [21,47].

3.2. Physicochemical Analysis of Biomaterials

The mycelium-based materials were characterized by scanning electron microscopy to determine the presence of hyphal fibers, which act as a binding agent in the biomaterial. Figure 5 shows scanning electron microscopy images of the biomaterials formed from Trametes versicolor and the substrate formed with the sludge. These images reveal the formation of filaments of different sizes corresponding to the hyphae of T. versicolor.

The hyphal extension rate of Trametes versicolor was evaluated to assess its potential as a biomaterial for construction applications. Figure 6 shows the radial extension in both media, MEA and PMMS, revealing that the radial growth rate in MEA increased daily while the growth rate in the PPMS medium remained constant. Additionally, an analysis of the cumulative growth in both media showed that the MEA slope was steeper than that of PPMS. This indicates a difference in nutrient availability between the two media. MEA provides simple molecules like sugars, readily available for fungal assimilation. In contrast, PPMS contains more complex molecules that require biochemical processes to be broken down and utilized by the fungi. A 6.02 mm/day growth rate was observed, slightly higher than the 5.27 mm/day reported in a previous study [48]. This suggests that Trametes versicolor could be a promising candidate for biomaterial production using PPMS, as its rapid hyphal growth would allow for the quick colonization of the support material and increased biomaterial production.

The hyphal diameter was also measured using SEM micrography and the ImageJ software. The hyphal mean diameter was close to 1.7 µm, as shown in Figure 7, higher than the hyphae diameter reported for Trametes versicolor in other substrates [49]. Thinner hyphae could affect the mechanical properties of the biomaterials, which will be evaluated in future studies.

Chemical characterization of biomaterials was carried out using FT IR-ATR spectroscopy to confirm the formation of a new biomaterial. Figure 8 shows the infrared spectrum of the biomaterials using the sludge and Trametes versicolor, revealing transmittance bands that disappear and appear compared with the substrate’s infrared spectrum, as seen in Figure 8. The characteristic bands in the range between 3595 cm⁻¹ and 3865 cm⁻¹ can be related to the O-H bond stretching due to the presence of cellulose. The peaks between 2800 cm⁻¹ and 2937 cm⁻¹ correspond to the asymmetric stretching of the C-H bond of the aromatic and aliphatic groups found in cellulose, hemicellulose, and lignin. The transmittance band at 1684 cm⁻¹ is related to the OH group of water absorbed in the sludge. The peaks at 1054 cm⁻¹ and 1030 cm⁻¹ correspond to cellulose’s asymmetric stretching of the C-O-C bonds [41,42].

3.3. Thermoacoustic Analysis of Biomaterials

The biomaterials obtained using T. versicolor on PMMS were analyzed using acoustic impedance, according to reference [40]. Table 4 shows the values of the sound absorption coefficients expressed as noise reduction indices (NRCs) and sound absorption (SAA), which were obtained for the biomaterial using the sludge as a substrate and Trametes versicolor. The biomaterial manufactured with T. versicolor on PMMS presented similar values to those reported for commercially available thermoacoustic insulators, such as expanded polyurethane and extruded polyurethane. However, its density was higher than that of traditional isolator materials [50], suggesting that it has potential as an alternative to commonly used acoustic insulation materials.

Table 5 shows the thermal conductivity of the biomaterials obtained using the KD-2 PRO thermal analyzer. These results reveal that the biomaterial had similar thermal values and conductivity coefficients lower than 0.1 W/m K, regardless of the type of substrate used. In addition, all biomaterials recorded values of thermal conductivity slightly higher than those of commonly used thermal insulation materials, such as fiberglass and extruded polystyrene [51,52]. These results demonstrate the potential of this type of biomaterial as a thermal insulator, which may represent a significant challenge that must be overcome to gain traction as a viable alternative in the construction industry.

3.4. Prospect for Large-Scale Industrial Use

This study demonstrated that mycelium-based materials produced from forestry waste, like PPMS, possess significant potential for large-scale industrial applications. These biomaterials exhibit high porosity, low density, excellent thermal insulation, and satisfactory sound absorption properties. Furthermore, they are fully compostable at the end of their lifecycle, promoting environmental sustainability [53]. However, for practical use at a large scale, there are still some challenges to be addressed:

1. The selection of fungal species: Using native fungi adapted to local conditions could make the production process more efficient and sustainable [32,54]. These fungi thrive in their local environment, leading to better and more consistent growth on forest debris. Alternatively, using economically damaging fungi such as Trametes versicolor [55], known for their efficiency in breaking down lignocellulosic materials, could reduce the energy required for incubation.

2. The optimization of growth parameters: The optimization of parameters such as temperature, humidity, aeration, and modularity to allow the exchange of energy and matter during the growth process could improve the properties and consistency of the final product [56].

3. Substrate quality: The contaminant and metal concentration, as well as the additional processing of the forest waste substrate, such as size reduction and pretreatment, could improve the homogeneity and performance of biomaterials [31,57,58].

4. Sterilization: For large-scale production, it is essential to investigate methods that enable the rapid sterilization of substrates, such as nuclear radiation, to ensure the development of microbiologically contamination-free biomaterials [59].

Further research and development are essential to overcome these challenges and enable large-scale industrial use. Optimizing growth parameters, improving substrate quality, maintaining homogeneity, and developing scalable sterilization techniques will be crucial for successfully implementing mycelium-based materials from forestry waste in various applications, such as thermal and acoustic insulation, in building construction.

4. Conclusions

Sludge generated by the pulp and paper industry is now being used as a raw material for sustainable construction biomaterials based on the mycelium of the fungus Trametes versicolor. Chemical, physical, microstructural, and surface analyses confirmed the formation of these new biomaterials. Acoustic impedance analyses revealed that these materials have a noise reduction coefficient and sound absorption average comparable to extruded polystyrene and polyurethane. In addition, the material’s thermal conductivity is near that of sheep wool. These mycelium-based materials produced from forestry waste possess significant potential for large-scale industrial applications due to their high porosity, low density, excellent thermal insulation, and satisfactory sound absorption properties. Therefore, they are an ecological and promising alternative to conventional construction materials.

Author Contributions

Conceptualization, H.M., P.M., F.C. and M.S.; methodology, H.M., P.M., I.A.U.-P., F.C., G.R.-G. and M.S.; validation, P.M., D.A.V. and M.S.; formal analysis, H.M., P.M., D.A.V. and M.S.; investigation, H.M., P.M. and M.S.; resources and data curation, H.M., I.A.U.-P. and P.M.; writing—original draft preparation, H.M., P.M., M.W. and M.S.; writing—review and editing, H.M., P.M., M.W. and M.S.; visualization, H.M., P.M. and M.S.; supervision, P.M., M.W. and M.S.; project administration, P.M. and M.S.; funding acquisition, M.S. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is unavailable due to privacy related to the Funder.

Acknowledgments

The authors thank ANID BASAL FB210015 CENAMAD and ANID Becas Doctorado Nacional 21231394.

Conflicts of Interest

The authors declare no conflicts of interest.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Figures and Tables

Figure 1. Schematic representation of mycelium-based material fabrication.

Figure 2. Photograph of biomaterials obtained using Trametes versicolor on PPMS.

Figure 3. ATR FT-IR spectrum of sludge.

Figure 4. X-ray diffraction pattern of sludge sample. The red lines highlight the diffraction peaks related to the crystalline cellulose phase, as mentioned in the previous paragraph.

Figure 5. SEM images of mycelium-based biomaterials using Trametes versicolor. (a) Exterior face; (b) interior face.

Figure 6. Radial extension of Trametes versicolor hyphae in MEA and PPMS. (a) Cumulative growth; (b) daily growth rate.

Figure 7. Hyphal diameter of biomaterials obtained using Trametes versicolor on PMMS.

Figure 8. ATR FT-IR spectrum of Trametes versicolor on PMMS.

Table 1

Physicochemical parameters of pulp and paper mill sludge. The range is a compilation from refs. [25,26,27,28,29].

Apparent Density(g/cm3)	Humidity(%)	pH	Cellulose(%)	Hemicellulose(%)	Lignin(%)
0.419–0.598	50–75	6.8–8.2	57–72	8.0–12.4	19.7–32.5

Table 2

Physicochemical parameters of sludge obtained from a local pulp and paper mill.

Humidity (%)	pH	Organic Matter Content (%)	Ash Content (%)	Color
85 ± 2	7.49 ± 0.07	11.45 ± 0.02	1.44 ± 0.1	Grayish

Table 3

Chemical composition of sludge (in mm/g) by atomic absorption spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS).

Ca	Na	K	As	Ba	B	Cd	V	Hg
1100.2 ± 5.7	3730 ± 1.7	1378 ± 4.0	4.3 ± 0.1	781.4 ± 2.2	135.5 ± 1.2	0.5 ± 0.01	38.7 ± 0.6	<0.25
Co	Cr	Cu	Mo	Ni	Pb	Se	Zn	Au
1.3 ± 0.01	5.6 ± 0.02	12.3 ± 0.1	3.2 ± 0.04	9.3 ± 0.2	1.5 ± 0.02	<0.22	94.7 ± 0.2	<0.23

Table 4

Sound absorption coefficients of materials.

Material	Density (g/cm3)	Noise Reduction Coefficient (NRC)	Sound Absorption (SAA)
Sludge biomaterial with T. versicolor	0.689	0.25 ± 0.02	0.25 ± 0.02
Expanded polyurethane	0.028	0.50	-
Extruded polyurethane	0.025	0.33	-

Table 5

Thermal absorption coefficients of biomaterials based on Trametes versicolor.

Material	Substrate	Thermal Conductivity Coefficient(W/m K)
Mycelium-based material	Sludge	0.052 ± 0.003
Fiberglass	Not applicable	0.033–0.045
Extruded polystyrene	Not applicable	0.025–0.035

References

1. Ardente, F.; Beccali, M.; Cellura, M.; Mistretta, M. Building Energy Performance: A LCA Case Study of Kenaf-Fibres Insulation Board. Energy Build.; 2008; 40, pp. 1-10. [DOI: https://dx.doi.org/10.1016/j.enbuild.2006.12.009]

2. Kulakovskaya, A.; Wiprächtiger, M.; Knoeri, C.; Bening, C.R. Integrated Environmental-Economic Circular Economy Assessment: Application to the Case of Expanded Polystyrene. Resour. Conserv. Recycl.; 2023; 197, 107069. [DOI: https://dx.doi.org/10.1016/j.resconrec.2023.107069]

3. Vila-Cortavitarte, M.; Lastra-González, P.; Calzada-Pérez, M.Á.; Indacoechea-Vega, I. Analysis of the Influence of Using Recycled Polystyrene as a Substitute for Bitumen in the Behaviour of Asphalt Concrete Mixtures. J. Clean. Prod.; 2018; 170, pp. 1279-1287. [DOI: https://dx.doi.org/10.1016/j.jclepro.2017.09.232]

4. Oswald, F. Recycling and Reutilisation Opportunities and Techniques of the Insulation Material EPS (Expanded Polystyrene) after the Lifetime of EIFS (Exterior Insulation Finishing System). Sustainability and Toxicity of Building Materials—Manufacture, Use and Disposal Stages; Elsevier: Amsterdam, The Netherlands, 2024; ISBN 9780323983365

5. Cerimi, K.; Akkaya, K.C.; Pohl, C.; Schmidt, B.; Neubauer, P. Fungi as Source for New Bio-Based Materials: A Patent Review. Fungal Biol. Biotechnol.; 2019; 6, pp. 1-10. [DOI: https://dx.doi.org/10.1186/s40694-019-0080-y]

6. Al-Qahtani, S.; Koç, M.; Isaifan, R.J. Mycelium-Based Thermal Insulation for Domestic Cooling Footprint Reduction: A Review. Sustainability; 2023; 15, 13217. [DOI: https://dx.doi.org/10.3390/su151713217]

7. Volk, R.; Schröter, M.; Saeidi, N.; Steffl, S.; Javadian, A.; Hebel, D.E.; Schultmann, F. Life Cycle Assessment of Mycelium-Based Composite Materials. Resour. Conserv. Recycl.; 2024; 205, 107579. [DOI: https://dx.doi.org/10.1016/j.resconrec.2024.107579]

8. Charpentier-Alfaro, C.; Benavides-Hernández, J.; Poggerini, M.; Crisci, A.; Mele, G.; Della Rocca, G.; Emiliani, G.; Frascella, A.; Torrigiani, T.; Palanti, S. Wood-Decaying Fungi: From Timber Degradation to Sustainable Insulating Biomaterials Production. Materials; 2023; 16, 3547. [DOI: https://dx.doi.org/10.3390/ma16093547]

9. Ghazvinian, A.; Farrokhsiar, P.; Vieira, F.; Pecchia, J.; Gursoy, B. Mycelium-Based Bio-Composites for Architecture. Mater. Res. Innov.; 2019; 2, pp. 505-514.

10. Attias, N.; Reid, M.; Mijowska, S.C.; Dobryden, I.; Isaksson, M.; Pokroy, B.; Grobman, Y.J.; Abitbol, T. Biofabrication of Nanocellulose–Mycelium Hybrid Materials. Adv. Sustain. Syst.; 2021; 5, 2000196. [DOI: https://dx.doi.org/10.1002/adsu.202000196]

11. Teixeira, J.L.; Matos, M.P.; Nascimento, B.L.; Griza, S.; Holanda, F.S.R.; Marino, R.H. Production and Mechanical Evaluation of Biodegradable Composites by White Rot Fungi. Ciênc. Agrotecnol.; 2018; 42, pp. 676-684. [DOI: https://dx.doi.org/10.1590/1413-70542018426022318]

12. Huang, D.; Guo, X.; Peng, Z.; Zeng, G.; Xu, P.; Gong, X.; Deng, R.; Xue, W.; Wang, R.; Yi, H. et al. White Rot Fungi and Advanced Combined Biotechnology with Nanomaterials: Promising Tools for Endocrine-Disrupting Compounds Biotransformation. Crit. Rev. Biotechnol.; 2018; 38, pp. 671-689. [DOI: https://dx.doi.org/10.1080/07388551.2017.1386613]

13. Harshvardhan, A.; Saikia, P. Microbial Bioremediation: A Sustainable Approach for Restoration of Contaminated Sites. Microbes in Agri-Forestry Biotechnology; CRC Press: Boca Raton, FL, USA, 2022; ISBN 9789811518119

14. Nussbaumer, M.; Van Opdenbosch, D.; Engelhardt, M.; Briesen, H.; Benz, J.P.; Karl, T. Material Characterization of Pressed and Unpressed Wood–Mycelium Composites Derived from Two Trametes Species. Environ. Technol. Innov.; 2023; 30, 103063. [DOI: https://dx.doi.org/10.1016/j.eti.2023.103063]

15. Xing, Y.; Brewer, M.; El-Gharabawy, H.; Griffith, G.; Jones, P. Growing and Testing Mycelium Bricks as Building Insulation Materials. IOP Conf. Ser. Earth Environ. Sci.; 2018; 121, 022032. [DOI: https://dx.doi.org/10.1088/1755-1315/121/2/022032]

16. Elsacker, E.; Vandelook, S.; Damsin, B.; Van Wylick, A.; Peeters, E.; De Laet, L. Mechanical Characteristics of Bacterial Cellulose-Reinforced Mycelium Composite Materials. Fungal Biol. Biotechnol.; 2021; 8, pp. 1-14. [DOI: https://dx.doi.org/10.1186/s40694-021-00125-4] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/34863310]

17. Zhang, X.; Hu, J.; Fan, X.; Yu, X. Naturally Grown Mycelium-Composite as Sustainable Building Insulation Materials. J. Clean. Prod.; 2022; 342, 130784. [DOI: https://dx.doi.org/10.1016/j.jclepro.2022.130784]

18. Bhagavathi, L.R.; Deshpande, A.P.; Ram, G.D.J.; Panigrahi, S.K. Effect of Cellulosic Fillers Addition on Curing and Adhesion Strength of Moisture-Curing One-Component Polyurethane Adhesives. Int. J. Adhes. Adhes.; 2021; 108, 102871. [DOI: https://dx.doi.org/10.1016/j.ijadhadh.2021.102871]

19. Marcuello, C.; Foulon, L.; Chabbert, B.; Molinari, M.; Aguié-Béghin, V. Langmuir-Blodgett Procedure to Precisely Control the Coverage of Functionalized AFM Cantilevers for SMFS Measurements: Application with Cellulose Nanocrystals. Langmuir; 2018; 34, pp. 9376-9386. [DOI: https://dx.doi.org/10.1021/acs.langmuir.8b01892]

20. Blauwhoff, D.; La Bianca, I. From Biomass to Mycelium Composite: An Exploration on Cellulose and Weed Residues; Stichting Toegepast Onderzoek Waterbeheer (STOWA): Amersfoort, The Netherlands, 2019.

21. Sayfutdinova, A.; Samofalova, I.; Barkov, A.; Cherednichenko, K.; Rimashevskiy, D.; Vinokurov, V. Structure and Properties of Cellulose/Mycelium Biocomposites. Polymers; 2022; 14, 1519. [DOI: https://dx.doi.org/10.3390/polym14081519]

22. Ghazvinian, A.; Gürsoy, B. Mycelium-Based Composite Graded Materials: Assessing the Effects of Time and Substrate Mixture on Mechanical Properties. Biomimetics; 2022; 7, 48. [DOI: https://dx.doi.org/10.3390/biomimetics7020048]

23. Sun, W.; Tajvidi, M.; Hunt, C.G.; McIntyre, G.; Gardner, D.J. Fully Bio-Based Hybrid Composites Made of Wood, Fungal Mycelium and Cellulose Nanofibrils. Sci. Rep.; 2019; 9, 3766. [DOI: https://dx.doi.org/10.1038/s41598-019-40442-8]

24. Quintana, E.; Valls, C.; Roncero, M.B. Valorization of Waste Paper Sludge as a Sustainable Source for Packaging Applications. Polym. Bull.; 2024; 81, pp. 9321-9345. [DOI: https://dx.doi.org/10.1007/s00289-024-05138-8]

25. Faubert, P.; Barnabé, S.; Bouchard, S.; Côté, R.; Villeneuve, C. Pulp and Paper Mill Sludge Management Practices: What Are the Challenges to Assess the Impacts on Greenhouse Gas Emissions?. Resour. Conserv. Recycl.; 2016; 108, pp. 107-133. [DOI: https://dx.doi.org/10.1016/j.resconrec.2016.01.007]

26. Turner, T.; Wheeler, R.; Oliver, I.W. Evaluating Land Application of Pulp and Paper Mill Sludge: A Review. J. Environ. Manag.; 2022; 317, 115439. [DOI: https://dx.doi.org/10.1016/j.jenvman.2022.115439]

27. Hazarika, J.; Khwairakpam, M. Evaluation of Biodegradation Feasibility through Rotary Drum Composting Recalcitrant Primary Paper Mill Sludge. Waste Manag.; 2018; 76, pp. 275-283. [DOI: https://dx.doi.org/10.1016/j.wasman.2018.03.044]

28. Jackson, M.J.; Line, M.A. Organic Composition of a Pulp and Paper Mill Sludge Determined by FTIR, 13 C CP MAS NMR, and Chemical Extraction Techniques. J. Agric. Food Chem.; 1997; 45, pp. 2354-2358. [DOI: https://dx.doi.org/10.1021/jf960946l]

29. Kim, J.S.; Lee, Y.Y.; Park, S.C. Pretreatment of Wastepaper and Pulp Mill Sludge by Aqueous Ammonia and Hydrogen Peroxide. Appl. Biochem. Biotechnol.; 2000; 84, pp. 129-139. [DOI: https://dx.doi.org/10.1385/ABAB:84-86:1-9:129]

30. Aiduang, W.; Chanthaluck, A.; Kumla, J.; Jatuwong, K.; Srinuanpan, S.; Waroonkun, T.; Oranratmanee, R.; Lumyong, S.; Suwannarach, N. Amazing Fungi for Eco-Friendly Composite Materials: A Comprehensive Review. J. Fungi; 2022; 8, pp. 1-28. [DOI: https://dx.doi.org/10.3390/jof8080842]

31. Elsacker, E.; Vandelook, S.; Brancart, J.; Peeters, E.; De Laet, L. Mechanical, Physical and Chemical Characterisation of Mycelium-Based Composites with Different Types of Lignocellulosic Substrates. PLoS ONE; 2019; 14, e0213954. [DOI: https://dx.doi.org/10.1371/journal.pone.0213954] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/31329589]

32. Jones, M.; Huynh, T.; John, S. Inherent Species Characteristic Influence and Growth Performance Assessment for Mycelium Composite Applications. Adv. Mater. Lett.; 2018; 9, pp. 71-80. [DOI: https://dx.doi.org/10.5185/amlett.2018.1977]

33. Collins, T.J. ImageJ for Microscopy. Biotechniques; 2007; 43, pp. S25-S30. [DOI: https://dx.doi.org/10.2144/000112517]

34. ISO 9427:2003 Wood-Based Panels—Determination of Density; The International Organization for Standardization: Geneva, Switzerland, 2003.

35. ISO 16979:2003 Wood-Based Panels—Determination of Moisture Content; The International Organization for Standardization: Geneva, Switzerland, 2003.

36. ASTM C1585-04 Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes; ASTM International: West Conshohocken, PA, USA, 2010.

37. ASTM D5334-08 Standard Test Method for Determination of Thermal Conductivity of Soil and Soft Rock by Thermal Needle Probe Procedure; ASTM International: Conshohocken, PA, USA, 2005.

38. Abdullah, A.; Mohamad, I.S.; Bani Hashim, A.Y.; Abdullah, N.; Wei, P.B.; Isa, M.H.M.; Abidin, S.Z. Thermal conductivity and viscosity of deionised water and ethylene glycol-based nanofluids. J. Mech. Eng. Sci.; 2016; 10, pp. 2249-2261. [DOI: https://dx.doi.org/10.15282/jmes.10.3.2016.4.0210]

39. ASTM E1050-24 Standard Test Method for Impedance and Absorption of Acoustical Materials Using a Tube, Two Microphones and a Digital Frequency Analysis System; ASTM International: Conshohocken, PA, USA, 2024.

40. Tao, J.; Wang, P.; Qiu, X.; Pan, J. Static flow resistivity measurements based on the ISO 10534.2 standard impedance tube. Build. Environ.; 2015; 94, pp. 853-858. [DOI: https://dx.doi.org/10.1016/j.buildenv.2015.06.001]

41. Hernández -Hernández, R.N.; Vázquez-García, R.Á.; Hernández-Ávila, J.; Veloz-Rodríguez, M.A.; Villagomez-Ibarra, J.R. Obtención de Celulosa Cristalina de Hoja de Maíz de Metztitlán Hidalgo. Pädi Bol. Cient. Cienc. Básicas Ing. ICBI; 2021; 9, pp. 7-12. [DOI: https://dx.doi.org/10.29057/icbi.v9iEspecial2.7993]

42. Yaras, A.; Arslanoğlu, H. Valorization of Paper Mill Sludge as Adsorbent in Adsorption Process of Copper (II) Ion from Synthetic Solution: Kinetic, Isotherm and Thermodynamic Studies. Arab. J. Sci. Eng.; 2018; 43, pp. 2393-2402. [DOI: https://dx.doi.org/10.1007/s13369-017-2817-3]

43. Han, J.S.; Kang, D.S.; Seo, Y.B. Application of In Situ Calcium Carbonate Process for Producing Papermaking Fillers from Lime Mud. ACS Omega; 2021; 6, pp. 3884-3890. [DOI: https://dx.doi.org/10.1021/acsomega.0c05688] [PubMed: https://www.ncbi.nlm.nih.gov/pubmed/33585767]

44. Clausi, M.; Pinto, D. Valorisation of Water Potabilization Sludges as Precursors for Alkali-Activated Binders: Characterization and Feasibility Study. Materials; 2023; 16, 1998. [DOI: https://dx.doi.org/10.3390/ma16051998]

45. Padmanabhan, S.K.; Lionetto, F.; Nisi, R.; Stoppa, M.; Licciulli, A. Sustainable Production of Stiff and Crystalline Bacterial Cellulose from Orange Peel Extract. Sustainability; 2022; 14, 2247. [DOI: https://dx.doi.org/10.3390/su14042247]

46. Ren, W.; Guo, F.; Zhu, J.; Cao, M.; Wang, H.; Yu, Y. A Comparative Study on the Crystalline Structure of Cellulose Isolated from Bamboo Fibers and Parenchyma Cells. Cellulose; 2021; 28, pp. 5993-6005. [DOI: https://dx.doi.org/10.1007/s10570-021-03892-w]

47. Sydor, M.; Cofta, G.; Doczekalska, B.; Bonenberg, A. Fungi in Mycelium-Based Composites: Usage and Recommendations. Materials; 2022; 15, 6283. [DOI: https://dx.doi.org/10.3390/ma15186283]

48. Schoder, K.A.; Krümpel, J.; Müller, J.; Lemmer, A. Effects of Environmental and Nutritional Conditions on Mycelium Growth of Three Basidiomycota. Mycobiology; 2024; 52, pp. 124-134. [DOI: https://dx.doi.org/10.1080/12298093.2024.2341492]

49. Alves, R.M.; Alves, M.L.; Campos, M.J. Morphology and Thermal Behaviour of New Mycelium-Based Composites with Different Types of Substrates. Progress in Digital and Physical Manufacturing, Proceedings of the ProDPM’19, Leiria, Portugal, 2–4 October 2019; Springer International Publishing: Berlin/Heidelberg, Germany, 2020; pp. 189-197. ISBN 9783030290405

50. Pedroso, M.; de Brito, J.; Silvestre, J.D. Characterization of Eco-Efficient Acoustic Insulation Materials (Traditional and Innovative). Constr. Build. Mater.; 2017; 140, pp. 221-228. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2017.02.132]

51. Yucel, K.T.; Basyigit, C.; Ozel, C. Thermal Insulation Properties of Expanded Polystyrene as Construction and Insulating Materials. Proceedings of the 15th Symposium on Thermophysical Properties; Boulder, CO, USA, 22–27 June 2003; pp. 54-66.

52. Lafond, C.; Blanchet, P. Technical Performance Overview of Bio-Based Expanded Polystyrene. Buildings; 2020; 10, 81. [DOI: https://dx.doi.org/10.3390/buildings10050081]

53. Shakir, M.A.; Ahmad, M.I. Bioproduct Advances: Insight into Failure Factors in Mycelium Composite Fabrication. Biofuels Bioprod. Biorefining; 2024; pp. 1-16. [DOI: https://dx.doi.org/10.1002/bbb.2620]

54. Livne, A.; Pearlmutter, D.; Gal, E.; Wösten, H.A.B. Increased CO₂ Fixation and Reduced Embodied Energy of Mycelium Bio-Composite Materials Grown on a Mixed Substrate over Diurnal Temperature Cycles. Constr. Build. Mater.; 2024; 421, 135566. [DOI: https://dx.doi.org/10.1016/j.conbuildmat.2024.135566]

55. Tišma, M.; Žnidaršič-Plazl, P.; Šelo, G.; Tolj, I.; Šperanda, M.; Bucić-Kojić, A.; Planinić, M. Trametes Versicolor in Lignocellulose-Based Bioeconomy: State of the Art, Challenges and Opportunities. Bioresour. Technol.; 2021; 330, 124997. [DOI: https://dx.doi.org/10.1016/j.biortech.2021.124997]

56. Bonga, K.B.; Bertolacci, L.; Contardi, M.; Paul, U.C.; Zafar, M.S.; Mancini, G.; Marini, L.; Ceseracciu, L.; Fragouli, D.; Athanassiou, A. Mycelium Agrowaste-Bound Biocomposites as Thermal and Acoustic Insulation Materials in Building Construction. Macromol. Mater. Eng.; 2024; 309, 2300449. [DOI: https://dx.doi.org/10.1002/mame.202300449]

57. Manan, S.; Ullah, M.W.; Ul-Islam, M.; Atta, O.M.; Yang, G. Synthesis and Applications of Fungal Mycelium-Based Advanced Functional Materials. J. Bioresour. Bioprod.; 2021; 6, pp. 1-10. [DOI: https://dx.doi.org/10.1016/j.jobab.2021.01.001]

58. Van Wylick, A.; Elsacker, E.; Yap, L.L.; Peeters, E.; de Laet, L. Mycelium Composites and Their Biodegradability: An Exploration on the Disintegration of Mycelium-Based Materials in Soil. Constr. Technol. Archit.; 2022; 1, pp. 652-659.

59. Williams, E.; Cenian, K.; Golsteijn, L.; Morris, B.; Scullin, M.L. Life Cycle Assessment of MycoWorks’ Reishi^TM: The First Low-Carbon and Biodegradable Alternative Leather. Environ. Sci. Eur.; 2022; 34, 120. [DOI: https://dx.doi.org/10.1186/s12302-022-00689-x]