Janetti, et al (2024) Thermal conductivity of biochar-clay composites for the internal insulation of buildings. Case Studies in Construction Materials. https://doi.org/10.1016/j.cscm.2024.e04083

Biochar-clay composites are emerging as an eco-friendly solution for internal insulation in buildings, offering sustainability and performance benefits. A recent study explored their thermal properties, focusing on how factors like biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More type, composite density, temperature, and moisture affect their effectiveness.

These composites combine biochar, a carbon-rich byproduct of biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More, with clay, a material known for its moisture-regulating properties. Together, they offer low thermal conductivity and high moisture buffering, making them suitable for energy-efficient renovations, especially in heritage buildings where external insulation isn’t an option.

The study tested various biochar-clay mixtures, measuring thermal conductivity under different conditions. At 20°C and dry conditions, composites with densities between 222–610 kg/m³ achieved thermal conductivities of 0.06–0.18 W/(m·K). Lighter composites with biochar from miscanthus biomass performed better thermally than those using denser biochar from biomass power plants. Adding natural fibers like straw improved strength without significantly affecting thermal performance.

Moisture and temperature were found to impact thermal conductivity. A 10°C temperature increase combined with 20 kg/m³ added moisture raised thermal conductivity by 10–26%, depending on the composite. This highlights the need to consider real-world conditions when applying these materials.

While the results are promising, further research is needed to optimize these composites for practical use, including understanding moisture dynamics and performance in real-world settings. This work positions biochar-clay composites as a sustainable alternative in modern insulation practices.