Biodegradable, scalable and flexible fiber membrane for green passive radiative cooling

The passive radiative cooling (PRC) approach allows zero-energy cooling by reflecting solar light and radiating heat simultaneously. However, most of the current PRC materials, especially polymer-based ones, are not able to be naturally degraded in the environment over a short time period when discarded, causing the current white pollution problem. Herein, we demonstrate a novel PRC material based on eco-friendly fiber membrane derived from biomass-derived silk fibroin (SF) and polylactic acid (PLA), which can be quickly degraded in outdoor soil environment for just one month. The resulting SF/PLA fiber membrane achieved ultra-high solar reflectance R‾solar and infrared emittance ε‾IR of 96.1% and ∼95.4%, respectively, and yielded an average sub-ambient cooling temperature of ∼6 °C even under a peak solar intensity of ∼900 W m−2 owing to its outstanding optical properties. In addition, large-scale products were prepared by simple and cost-effective electrostatic spinning-based manufacturing process. This study offers a new strategy that combines biodegradation with zero-energy cooling and shows great potential for widespread future applications, substantially decreasing energy consumption and carbon emission. •A novel green passive radiative cooling fiber membrane that can be quickly degraded in soil environment is fabricated.•The fiber membrane achieves extremely high average solar absorbance (∼96.1%) and average infrared emittance (∼95.4%).•The fiber membrane yields an average sub-ambient cooling temperature of ∼6 °C even under solar intensity of ∼900 W m−2.•The fabrication process is simple and cost-effective, offering the possibility of preparing large-scale products.