Enhanced thermal insulation of biochar-gypsum composites

Low-carbon and energy-efficient construction materials are crucial in mitigating the environmental impact of the construction industry while enhancing energy efficiency within buildings. Here, we developed sustainable, lightweight biochar-gypsum composites with enhanced thermal insulation properties for building applications. Biochar, a wood waste-derived carbon-negative material in this study, was integrated into gypsum plaster at various dosages to assess its impact on thermal insulation and mechanical performance. The results demonstrated that biochar addition significantly reduced thermal conductivity, with a maximum reduction of 65% (from 0.77 to 0.27 W/(m·K)) at 60 wt% biochar with pores as thermal barriers. Simulation results revealed that irregular heat flux pathways could alleviate heat transfer by delaying temperature equilibration across the biochar-gypsum composites. However, a high biochar content reduced mechanical properties, with compressive strength decreasing from 22.3 MPa (0 wt%) to 1.7 MPa (60 wt%). Moderate biochar addition (20 wt%) balanced the overall performance, reducing thermal conductivity by 40% while maintaining a compressive strength of 4.7 MPa. These findings highlight biochar-gypsum composites as eco-friendly construction materials that can enhance energy efficiency and foster waste valorisation in sustainable construction.