Spent mushroom substrates (SMS), a lignocellulosic residue from mushroom cultivation, represent a promising raw material for the valorization of nontoxic materials supporting the circular bioeconomy. The inherent biological pretreatment of the birch wood substrate during shiitake cultivation reduces the need for chemicals prior to fibrillation. SMS was fibrillated using an extruder and a blender at high (28 wt %) and low (5 wt %) solid contents, respectively, with and without a predispersion step. Extrusion proved to be the most energy-efficient method, requiring only 11 kWh/t, compared with 417 kWh/t for blending. When combined with predispersion, extrusion is the second most energy-efficient fibrillation method (789 kWh/t), compared to blending with predispersion (1195 kWh/t). Microscopy and fiber fractionation confirmed fibrillation into microfibers after extrusion and the presence of residual mycelium. Sheet formation by vacuum filtration over a coarse mesh significantly lowered the filtration time compared to a fine filter. Sheets produced from fibrillated SMS possessed tensile strength up to 7.5 times higher than commercial birch kraft pulp sheets prepared under the same conditions. The improved tensile strength is due to the presence of mycelial fibrils, which enhanced fiber–fiber bonding. Overall, extrusion provides a scalable, energy-efficient route for SMS fibrillation for the production of future all-natural materials without the need for chemical modification.

Thin, high-performance separators are crucial for enhancing the volumetric energy density of electrochemical energy storage devices. Cellulose nanofibril networks are promising candidates due to their intrinsic hydrophilicity and ability to form thin, mechanically strong networks. In this study, wood particles were directly TEMPO-oxidized and fibrillated into nanofibrils (TOCNF) using a microfluidizer, and their resulting networks were tailored with kraft lignin via a simple mixing and casting approach. The influence of lignin content on separator properties and supercapacitor performance was systematically evaluated. The modified networks were compared with pristine TOCNF networks and commercial polyolefin separators. An optimal lignin content of 10 wt% provides the best balance of properties, combining high electrolyte uptake (∼280 wt%), good wet tensile strength (∼6 MPa), and sufficient thermal stability. Supercapacitors assembled with this separator delivered high specific capacitance (112.1 F g−1 at 0.5 A g−1), low series resistance (2.4 Ω), and stable, symmetric charge–discharge behavior. Increasing lignin content to 20 and 30 wt% led to reduced mechanical integrity and electrochemical performance. Overall, the bio-based separators outperformed the commercial reference, highlighting lignin-tailored TOCNF networks as sustainable and high-performance alternatives for next-generation energy storage applications.

Underutilized co- and by-products are upgraded into materials with functional properties. The utilization of mushroom farming residues is investigated, specifically mushroom residues and spent mushroom substrate – whose chemical composition is determined – to produce cosmetic face masks, packaging films, and oil sorbents. Flexible mushroom sheets exhibit conformability and antioxidant activity between 82 and 94%, and better tensile strength in comparison with commercial cosmetic masks, making them suitable for such applications. Plasticization with glycerol increases the flexibility and tensile strain from ≈1 to 45% and moisture sorption from 32 to 100 wt.%. Spent mushroom substrate pulp yields stiff and strong rigid sheets with Young's moduli of 5 GPa and tensile strengths of 42 MPa. These sheets show 100% antioxidant activity, having hydrophobic behavior and oxygen barrier properties in dry conditions, and thus are promising for bioactive packaging applications. Foamed spent mushroom substrate sorbents demonstrate high affinity for both oil and water, with a water and oil uptake of 21 and 28 times their weight, respectively, while maintaining structural integrity. These properties make the foams viable as bio-based oil sorbents, highlighting the potential of by-products for advanced functional materials.

Cellulose filaments with a unique microtape-like shape (width/thickness ratio ≈ 40) were studied for their potential as reinforcement in bio-epoxy resin with the hypothesis that their gross-sectional geometry would allow for efficient stress transfer and a higher transverse modulus. The microstructure of the spun filaments, orientation of the cellulose fibrils within them, and their mechanical properties were analyzed. Unidirectional (UD) composites with bio-epoxy resin were fabricated using vacuum infusion resulting in filament content of ≈ 23 vol% and low density 1.18 gcm−3.

Wide-angle X-ray scattering showed that the cellulose fibrils were relatively well aligned in the filament axis, having an orientation factor of 0.78. The axial filament modulus was measured to 33 GPa, the in-plane transverse modulus to 12 GPa and the axial strength was approx. 380 MPa. The longitudinal E-modulus of the UD composites was measured to 10 GPa and the strength to 120 MPa, both 3 times higher than the used bio-epoxy agreeing well with the estimated values. The transverse elongation at break of the UD composite was higher than typical values reported for glass-fiber epoxy composites, but the effect of filament shape on the transverse modulus was less significant than the predicted 4.5 GPa but still better than estimated for circular fibers. The lower property is likely due to the low filament content and the partially uneven in-plane filament arrangement. Simulations based on shear stress analysis suggest that the transverse properties of the UD composite could be improved by ensuring that the filament planes remain predominantly parallel in-plane during fabrication, and the overall mechanical properties could be improved by increasing the filament content.

Bioflex is a biodegradable polymer blend combining poly(butylene adipate-co-terephthalate) (PBAT) and bio-based poly(lactic acid) (PLA), offering properties comparable to polyethylene. However, challenges like limited processability and low mechanical properties restrict its use to agricultural films. In this study, fibers from end-of-life textiles (polyester, viscose, cotton, and silk) are used to address these limitations, demonstrating a resource-efficient approach to reducing landfill deposits. Adding fibers to the polymer blend (30 wt%) visibly improves the melt strength. The end-of-life fibers affect the mechanical properties in different ways: polyester fibers almost double the tensile strength, viscose fibers triples flexural strength, and silk fibers lead to the highest compressive strength. The retained colors of the fibers further contribute to vibrant composites, making them ideal for cosmetics packaging, household goods, fashion accessories, and toys. Additionally, the composting test revealed varied disintegration behaviors. Cotton and silk began disintegrating first, viscose followed, while polyester showed no disintegration, extending the composite's durability in use. This study highlights the potential of end-of-life textiles as an excellent reinforcement for Bioflex copolymer blends, promoting efficient resource use, reducing environmental waste, and unlocking new application areas for biodegradable polymers.

Utilization of biomass and reuse of industrial by-products and their sustainable and resource-efficient development into products that are inherently non-toxic is important to reduce the use of hazardous substances in the design, manufacture and application of biomaterials. The hypothesis in this study is that spent mushroom substrate (SMS), a by-product from mushroom production, has already undergone a biological pretreatment and thus, can be used directly as a starting material for fibrillation into value-added and functional biomaterial, without the use of toxic substances. The study show that SMS can be effectively fibrillated at a very high concentration of 6.5 wt % into fibrils using an energy demand of only 1.7 kWh kg−1, compared to commercial and chemically pretreated wood pulp at 8 kWh kg−1, under same processing conditions. SMS is a promising resource for fibrillation with natural antioxidant activity and network formation ability, which are of interest to explore further in applications such as packaging. The study shows that biological pretreatment can offer lower environmental impact related to toxic substances emitted to the environment and thus contribute to reduced impacts on categories such as water organisms, human health, terrestrial organisms, and terrestrial plants compared to chemical pretreatments.

Natural fibers have gained popularity for reinforcing polymers due to their renewability, biodegradability, and usually have lower costs than synthetic fibers. The demand to reduce environmental impact has heightened awareness of the importance of adopting resource-efficient alternatives in line with recycling, reusing, and responsible consumption practices. This study integrates resource-efficient use of materials using a co-rotating twin screw extruder (TSE) in the development of biocomposites as an alternative for recycling, reducing landfill disposal, and contributing to the circular economy. 

The influence of recycling wood-polymer composites (WPCs) was explored by subjecting the materials to nine extrusion cycles. The properties of the WPCs were evaluated after every other cycle and compared to those of virgin and recycled polypropylene (PP) and WPCs. The results revealed that, although shear forces during extrusion decreased the aspect ratio of the wood fibers and reduced tensile strength after nine recycling cycles, the WPC still maintained higher mechanical properties than virgin PP, highlighting the advantages of using recycled WPC over PP. Recycling WPCs reduces the overconsumption of fossil-based plastics, decreases landfill disposal, and lessens the need for virgin fibers. 

The valorization of end-of-life textiles was studied as a potential candidate for use in biocomposites. The primary challenge was to develop a low-energy consumption method for feeding, fibrillating, and compounding textiles with thermoplastic polymers without requiring chemical or mechanical pretreatments. A continuous extrusion process, recycled-textile long fiber thermoplastic (RT-LFT), was developed to incorporate end-of-life textiles into a PP matrix using a co-rotating TSE. The results demonstrated that RT-LFT is a direct, effective, and energy-efficient method for compounding end-of-life textiles with polymer, enabling the textiles to be separated into individual fibers that are well dispersed within the matrix. 

In addition, the performance of fibers from end-of-life textiles was also evaluated using PP, and Bio-flex a biodegradable blend of polybutylene adipate terephthalate (PBAT)/ polylactic acid (PLA). The addition of the fibers did not show improvements in the mechanical properties of the PP matrix but showed great enhancement for the Bio-flex matrix. Adding fibers also improved the flow properties and melt strength of the polymers. Moreover, the disintegration under compositing conditions showed that the addition of fibers delayed the process when compared to neat polymer, but after 75 days cotton and silk biocomposites began to disintegrate. 

WPCs are often modified with fossil-based virgin elastomers to enhance their impact and toughness properties. However, the use of these elastomers increases competition for limited resources and raises the costs of WPCs. To address this, the influence of recycled materials as impact modifiers in WPCs was investigated by replacing virgin elastomer with recycled fibers from end-of-life textiles and recycled elastomer. The results indicated that both recycled materials are viable alternatives to virgin elastomer, offering comparable impact and toughness properties while reducing the WPCs' carbon footprint and costs. 

In conclusion, using recycled or end-of-life materials presents an excellent alternative to virgin materials in biocomposites. It contributes to the circular economy, reduces landfill waste, decreases material costs, enhances resource efficiency, promotes recycling, and adds value to end-of-life materials. 

Wood–polymer composites (WPCs) with polypropylene (PP) matrix suffer from low toughness, and fossil-based impact modifiers are used to improve their performance. Material substitution of virgin fossil-based materials and material recycling are key aspects of sustainable development and therefore recycled denim fabric, and elastomer were evaluated to replace the virgin elastomer modifier commonly used in commercial WPCs. Microtomography images showed that the extrusion process fibrillated the denim fabric into long, thin fibers that were well dispersed within the WPC, while the recycled elastomer was found close to the wood fibers, acting as a soft interphase between the wood fibers and PP. The fracture toughness (KIC) of the WPC with recycled denim fabric matched the commercial WPC which was 1.4 MPa m1/2 and improved the composite tensile strength by 18% and E-modulus by 54%. Recycled elastomer resulted in slightly lower KIC, 1.1 MPa m1/2, as well as strength and modulus while increasing elongation and contributing to toughness. The results of this study showed that recycled materials can potentially be used to replace virgin fossil-based elastomeric modifiers in commercial WPCs, thereby reducing the CO2 footprint by 23% and contributing to more efficient use of resources.

This study aimed to develop a manufacturing process for recycled textile long fiber thermoplastics (RT-LFT) and thereby contribute to circular economy. Three different post-consumer textiles (cotton denim and plain weave, and silk plain weave) were cut into strips and fed directly into a co-rotating twin-screw extruder in which the textile was fibrillated and compounded with polypropylene (PP). The fibrillation of the textile, fiber dispersion, and interaction with the matrix polymer were studied, and the thermal and mechanical properties of the composites were evaluated. For example, cotton denim composites containing 30 wt% fiber content resulted in 26% increase in yield strength and a 72% increase in modulus when compared with that of PP. The RT-LFT process is a straightforward method for transforming used textiles into composites like cups and bottoms, offering advantages such as reduced manufacturing costs, add value for waste material, and lower carbon emissions.

In this study, the possibility of adding nanocellulose and its dispersion to polyamide 6 (PA6), a polymer with a high melting temperature, is investigated using melt extrusion. The main challenges of the extrusion of these materials are achieving a homogeneous dispersion and avoiding the thermal degradation of nanocellulose. These challenges are overcome by using an aqueous suspension of never-dried nanocellulose, which is pumped into the molten polymer without any chemical modification or drying. Furthermore, polyethylene glycol is tested as a dispersant for nanocellulose. The dispersion, thermal degradation, and mechanical and viscoelastic properties of the nanocomposites are studied. The results show that the dispersant has a positive impact on the dispersion of nanocellulose and that the liquid-assisted melt compounding does not cause the degradation of nanocellulose. The addition of only 0.5 wt.% nanocellulose increases the stiffness of the neat polyamide 6 from 2 to 2.3 GPa and shifts the tan δ peak toward higher temperatures, indicating an interaction between PA6 and nanocellulose. The addition of the dispersant decreases the strength and modulus but has a significant effect on the elongation and toughness. To further enhance the mechanical properties of the nanocomposites, solid-state drawing is used to create an oriented structure in the polymer and nanocomposites. The orientation greatly improves its mechanical properties, and the oriented nanocomposite with polyethylene glycol as dispersant exhibits the best alignment and properties: with orientation, the strength increases from 52 to 221 MPa, modulus from 1.4 to 2.8 GPa, and toughness 30 to 33 MJ m−3 in a draw ratio of 2.5. This study shows that nanocellulose can be added to PA6 by liquid-assisted extrusion with good dispersion and without degradation and that the orientation of the structure is a highly-effective method for producing thermoplastic nanocomposites with excellent mechanical properties.