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 epsilon(IR) of 96.1% and similar to 95.4%, respectively, and yielded an average sub-ambient cooling temperature of-6 degrees C even under a peak solar intensity of similar to 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 con-sumption and carbon emission.