Electrochemical Upcycling of Shell Waste for Sustainable Nutrient Recovery from Wastewater

The increasing global population has boosted fertilizer demand for food production, food waste generation, and water pollution. Here, we report an electrochemical strategy to upcycle shell waste for nutrient reclamation from wastewater to tackle these challenges in one shot, in which shell waste is decomposed by anodic-produced H⁺, supplying cations (i.e., Ca²⁺ and Mg²⁺). Meanwhile, cathode-derived alkaline promotes the crystallization of nutrients (i.e., PO₄^3- and NH₄⁺) from the wastewater. We first validated this concept's promising P reclamation (84.2-99.2%) toward three common real wastewaters with P levels ranging from 7 to 1577 mg/L, indicating its potential for diverse applications. We further designed a scalable prototype for eggshells upcycling and P-fertilizer production from urine in a household setting, showing encouraging performance P recovery (>85.7% at 1.0 kW h/m³), reduced CO₂ emissions by 76.5%, and promising economic viability. Our work outlines a sustainable map for managing food waste, harvesting nutrients from wastewater, and eliminating water pollution.