Evaluation of Resource Efficiency and Environmental Impact in a Plant Factory Using an Ion-Selective Electrode-Based Precision Nutrient Management System

Plant factories enable stable crop production, but face sustainability challenges due to intensive resource consumption. In particular, studies that quantitatively analyze nutrient use in plant cultivation and assess the environmental burdens remain scarce. To address this, this study developed and evaluated a precision nutrient management system using ion-selective electrodes (ISEs) for closed hydroponic lettuce cultivation. The system’s performance was compared with a conventional EC-based approach in terms of resource use efficiency and environmental impact using life cycle assessment (LCA). The ISE-based system effectively maintained NO3, K, and Ca concentrations within target ranges (root mean square error (RMSE) < 52 mg·L−1), producing healthy crops without the physiological disorders (tip-burn) observed in the EC-based control, while the EC-based system showed higher total fresh weight, which implies that the increase in fresh weight may not necessarily correspond to marketable yield due to the nutrient imbalances. In terms of efficiency, the ISE-based system improved water-use efficiency (WUE) by 48.4% and fertilizer-use efficiency (FUE) by 24.5%. Furthermore, LCA revealed that the ISE-based system reduced greenhouse gas emissions by 8% and freshwater ecotoxicity by 64% per kg of lettuce, primarily by extending the nutrient solution reuse period threefold. The results suggest that ion-specific precision management has the potential to enhance the sustainability and resource efficiency of plant factories.