Sustainable and Cost‐Effective Solar Steam Generation via Biochar‐Modified Natural Sponge Evaporator

Abstract Water scarcity is a critical global issue, and solar steam generation (SSG) using photothermal materials offers a sustainable solution for desalination. However, high costs and complex fabrication often limit their practicality. In this study, a low‐cost SSG system is developed by modifying a commercial cellulosic sponge with carbonized Turkish tea waste (CTW). The CTW, obtained via pyrolysis, provided strong light absorption and efficient photothermal conversion, while the sponge served as a lightweight, self‐floating substrate with rapid water uptake. The resulting CTW‐S composite achieved a water evaporation rate of 1.42 kg m ⁻² h ⁻¹ and a solar‐to‐vapor conversion efficiency of 83% under one sun illumination. This work demonstrates the potential of biomass‐derived materials for scalable, eco‐friendly, and low‐cost water treatment applications.