Biomass-based mineralized chitin microsheets for high-efficiency radiative cooling

The increasing frequency of extreme heat events under global climate change, combined with high energy consumption and CO₂ emissions from conventional cooling systems, threatens both ecological sustainability and human health. While traditional passive radiative cooling materials offer a potential solution, they often lead to pollution and have complex designs with high costs. To address these limitations, we developed Mineralized Chitin-based Composite Microsheets (MCCM), a low-cost, eco-friendly radiative cooling material derived from shrimp shells. By leveraging the natural mineralized multiscale Bouligand structure of shrimp shells, we designed a simple chemical treatment to remove proteins, lipids, and pigments while preserving its multiscale structure. Under solar irradiation, MCCM enables sub-ambient radiative cooling, achieving an average temperature reduction of 4.5 °C, attributed to its high solar reflectance (90.0 %) and mid-infrared emissivity (96.0 %). When applied to building exteriors and rooftops, MCCM significantly enhances annual energy-saving performance (>80 GJ) and effectively reduces CO₂ emissions. Additionally, it exhibits excellent thermal stability and flame retardancy and can be recycled as agricultural fertilizer, further enhancing its sustainability. This simple processing method for high-value utilization of waste shrimp shells offers a novel approach to developing low-cost functional materials and recycling biomass waste, demonstrating significant potential for building temperature management.