Biochar-derived shape-stabilized phase change materials for sustainable building applications: Progress, performance, and future outlook

In terms of energy efficiency, the utilization of phase change materials has been proven to be a viable approach for lowering energy usage while maintaining indoor thermal comfort. Nevertheless, PCM leakage during melting is a major challenge for effective functioning. Therefore, traditional supporting materials for shape-stabilized PCMs (ssPCMs), such as expanded perlite, vermiculite, pumice, and zeolite, have significant limitations. Natural resources typically have low impregnation ratios, which limits their practical performance. Biochar, on the other hand, is created from a variety of waste resources. This provides a sustainable and highly efficient alternative support for PCMs. The porous structure, significant surface area (up to 2000 m 2 /g), and surface functional groups of biochar allow it to encapsulate significant amounts of PCMs without leakage. Furthermore, its production promotes circular economy concepts via carbon sequestration and waste valorization. The present review addresses biochar-based ssPCMs and their use in buildings. We investigate biochar manufacturing methods, modification approaches, and PCM impregnation to improve thermal and structural characteristics. The utilization of these composites in buildings is also reviewed, including their effects on compressive strength, thermal performance, and economic and environmental impact. The overall review concludes by summarizing the key findings and offering recommendations for future studies toward more effective advancements and scalable approaches.