<p>Radiative cooling materials, which passively dissipate heat by reflecting sunlight and emitting infrared radiation through the atmospheric window, hold transformative potential for energy-efficient and sustainable thermal management. In particular, biomass-derived coolers have gained attention for their natural optical properties and environmental compatibility. However, such materials often depend on energy-intensive or complex processing to achieve the necessary photonic structures, while their limited mechanical strength and durability restrict practical outdoor application. Here, we report a high-performance, fully recyclable radiative cooling biocomposite fabricated directly from natural wood through an energy-efficient top-down approach that combines multi-stage crystalline restructuring with nanostructural assembly. This design synergistically combines enhanced cellulose crystallinity, capillary-driven self-densification, and hydrogen-bonded nanofiller networks to achieve exceptional mechanical properties (416.7 MPa tensile strength) and unprecedented cooling power (106 W/m²), surpassing most conventional cooling materials. During the daytime, field tests validate 8.8 °C sub-ambient temperature reduction under 879 W/m² solar irradiance. The cooling biocomposite, produced at scale via particle-solution shock process, exhibits high recyclability and foldability, completing an environmentally conscious life cycle. The energy‑efficient manufacturing process enables meter‑scale production, offering a promising pathway toward carbon‑neutral thermal management in sustainable buildings and agricultural applications.</p>