High-Efficiency Solar Steam Generation Using a Biochar-Modified Sponge Evaporator Derived from Turkish Coffee Waste

Solar seawater desalination represents a sustainable approach to addressing the global freshwater shortage. Nevertheless, the high cost of photothermal materials remains a significant obstacle to the large-scale production of solar steam generation (SSG) systems. Herein, we developed a cost-effective photothermal evaporator (CTCW-S) by integrating carbonized Turkish coffee waste (CTCW) with a commercially available, hydrophilic, self-floating cellulosic sponge (S). The CTCW was obtained through pyrolysis of collected coffee waste, yielding a porous carbonaceous material with strong photothermal properties. The combination of the sponge's rapid water absorption capability and the adequate solar absorption efficiency of the CTCW enabled the resulting material to generate efficient steam. Under one solar illumination, CTCW-S demonstrated a water evaporation rate of 1.63 kg m^-2 h^-1 and a solar-to-vapor conversion efficiency of 81%. These results underscore the potential of CTCW-S as a cost-effective and scalable solution for water purification and seawater desalination. Utilizing biomass-derived waste in photothermal materials presents a novel and sustainable approach to addressing global freshwater scarcity.