ORS7-1332
Bio-Based resin bio-composites reinforced with biochar/hydrochar for Sustainable Facade Applications
Topic
S7. Innovations in Polymeric Composites: From Design and Processing to Industrial Applications
When and Where
Sep 30, 2026
12:05 - 12:20
Room 107
Session Chairs
Seokhoon AHN
Presenter(s)
Luis Cutz (TU Delft)
Co-Author(s)
Abstract
Introduction
Facade systems account for a significant share of the embodied carbon in building envelopes, driven largely by petroleum-derived polymer matrices and energy-intensive bulk moulding compounds (BCMs). On the polymer side, facade composite matrices are broadly divided into thermosets and thermoplastics. Thermoplastics (e.g., PE, PP, PVC) dominate wood-plastic composite cladding for their recyclability and extrusion compatibility, while thermosets (e.g., polyester, epoxy, rubber, and furan resins) offer greater dimensional stability, rigidity, and thermal resistance at the cost of reprocessability. In the context of bio-based and durable composite materials, furan resins are particularly relevant because they can be derived from renewable resources and are known for their chemical resistance, thermal stability, and durability. Therefore, a novel furan resin is used as the thermoset matrix in the present work.
Conventional BMCs use mineral fillers such as calcium carbonate and glass fiber because they are inexpensive, readily available, and effective in improving processability and dimensional stability. However, increasing interest in more sustainable composite materials has encouraged the investigation of renewable fillers derived from biomass such as biochar. While biochar has been explored as a sustainable fuel or soil amendment, its use in facade-grade composites for the building envelope remains limited, primarily due to poor interfacial compatibility with polymer matrices, which constrains mechanical performance, moisture resistance, and processability. This study addresses this knowledge gap by evaluating hydrothermal carbonization- and pyrolysis-derived chars as fillers in bio-based furan resin composites, benchmarking their performance against facade application requirements, with a primary focus on enhancing mechanical properties and weather resistance. In addition, the unique aspect of this study is that it was conducted in partnership with a Dutch company, ensuring that the outcomes of this work can be scaled up from prototype to commercial level.
Materials and Methods
Biochar was produced from almond shells via pyrolysis at 400-800°C, and hydrochars were produced at 260-280°C. The bio-composite production process comprised three successive stages: filler drying, dough preparation, and compression moulding. Prior to panel production, the filler material was dried in a laboratory oven at 105°C for two hours to minimize its moisture content and to ensure reproducible processing conditions. The composite dough was prepared in a blade mixer, where a furan bio-based resin was stirred under vacuum to remove residual moisture. Subsequently, the filler (25wt%-43wt% loading) was gradually added to the resin mixture. The prepared dough was processed into flat panels by means of compression moulding. Mechanical properties were assessed via three-point bending test and charpy impact testing. Thermal behavior was characterized via TGA/DSC. Morphology and filler matrix-interaction were examined via SEM-EDS, FTIR and BET. Wettability was measured using contact angle measurements of water.
Results
Biochars and hydrochars produced from almond shells have an average fixed carbon content of 85wt% and 48wt%, respectively. Compared with the raw almond shell, the hydrochar FTIR spectra indicate a mild transformation stage. The persistence of O–H, C=O, C–O, and C–O–C bands shows that HTC preserves oxygen-containing functional groups to a significant extent. On the other hand, the reduction of polar functional groups in the biochar's FTIR results suggests that pyrolysis produces a less hydrophilic and more carbonized filler compared with both the raw almond shell and the hydrochars.
Based on preliminary findings, bio-based resin biocomposites reinforced with biochar at 400°C had an average modulus of 3.17 GPa and flexural strength of 46 MPa. Preliminary findings for bio-based resin biocomposites reinforced with hydrochar at 260°C show an average modulus of 2.18 GPa and flexural strength of 36 MPa.
Conclusion
Preliminary results establish biochar and hydrochar as viable, carbon-negative fillers for bio-based facade composites, achieving similar flexural strengths as reported in literature for bio-based bio-composites (43-50 MPa). The best reinforcement observed thus far was at 37wt% loading, demonstrating that these bio-based composites are not only a promising solution for the building environment but also for valorizing low-grade residues such as almond shells.
Facade systems account for a significant share of the embodied carbon in building envelopes, driven largely by petroleum-derived polymer matrices and energy-intensive bulk moulding compounds (BCMs). On the polymer side, facade composite matrices are broadly divided into thermosets and thermoplastics. Thermoplastics (e.g., PE, PP, PVC) dominate wood-plastic composite cladding for their recyclability and extrusion compatibility, while thermosets (e.g., polyester, epoxy, rubber, and furan resins) offer greater dimensional stability, rigidity, and thermal resistance at the cost of reprocessability. In the context of bio-based and durable composite materials, furan resins are particularly relevant because they can be derived from renewable resources and are known for their chemical resistance, thermal stability, and durability. Therefore, a novel furan resin is used as the thermoset matrix in the present work.
Conventional BMCs use mineral fillers such as calcium carbonate and glass fiber because they are inexpensive, readily available, and effective in improving processability and dimensional stability. However, increasing interest in more sustainable composite materials has encouraged the investigation of renewable fillers derived from biomass such as biochar. While biochar has been explored as a sustainable fuel or soil amendment, its use in facade-grade composites for the building envelope remains limited, primarily due to poor interfacial compatibility with polymer matrices, which constrains mechanical performance, moisture resistance, and processability. This study addresses this knowledge gap by evaluating hydrothermal carbonization- and pyrolysis-derived chars as fillers in bio-based furan resin composites, benchmarking their performance against facade application requirements, with a primary focus on enhancing mechanical properties and weather resistance. In addition, the unique aspect of this study is that it was conducted in partnership with a Dutch company, ensuring that the outcomes of this work can be scaled up from prototype to commercial level.
Materials and Methods
Biochar was produced from almond shells via pyrolysis at 400-800°C, and hydrochars were produced at 260-280°C. The bio-composite production process comprised three successive stages: filler drying, dough preparation, and compression moulding. Prior to panel production, the filler material was dried in a laboratory oven at 105°C for two hours to minimize its moisture content and to ensure reproducible processing conditions. The composite dough was prepared in a blade mixer, where a furan bio-based resin was stirred under vacuum to remove residual moisture. Subsequently, the filler (25wt%-43wt% loading) was gradually added to the resin mixture. The prepared dough was processed into flat panels by means of compression moulding. Mechanical properties were assessed via three-point bending test and charpy impact testing. Thermal behavior was characterized via TGA/DSC. Morphology and filler matrix-interaction were examined via SEM-EDS, FTIR and BET. Wettability was measured using contact angle measurements of water.
Results
Biochars and hydrochars produced from almond shells have an average fixed carbon content of 85wt% and 48wt%, respectively. Compared with the raw almond shell, the hydrochar FTIR spectra indicate a mild transformation stage. The persistence of O–H, C=O, C–O, and C–O–C bands shows that HTC preserves oxygen-containing functional groups to a significant extent. On the other hand, the reduction of polar functional groups in the biochar's FTIR results suggests that pyrolysis produces a less hydrophilic and more carbonized filler compared with both the raw almond shell and the hydrochars.
Based on preliminary findings, bio-based resin biocomposites reinforced with biochar at 400°C had an average modulus of 3.17 GPa and flexural strength of 46 MPa. Preliminary findings for bio-based resin biocomposites reinforced with hydrochar at 260°C show an average modulus of 2.18 GPa and flexural strength of 36 MPa.
Conclusion
Preliminary results establish biochar and hydrochar as viable, carbon-negative fillers for bio-based facade composites, achieving similar flexural strengths as reported in literature for bio-based bio-composites (43-50 MPa). The best reinforcement observed thus far was at 37wt% loading, demonstrating that these bio-based composites are not only a promising solution for the building environment but also for valorizing low-grade residues such as almond shells.
