Life Cycle Assessment of Capacitive Deionization Technology

Clean and stable water supply is one of the pressing global challenges. Desalination serves as a sustainable alternative to mitigate the water stress. However, it high electricity consumption during operation phase usually result in major environmental impacts. Capacitive deionization (CDI) is regarded as a promising desalination technology due to its unique properties of low-energy and environmental-friendliness. This study aims at evaluating the resource demands as well as their associated environmental impacts of a laboratory scale CDI system using life cycle assessment (LCA) approach. Empirical measurements from a laboratory-scale CDI system developed by our research group are used for the inventory analysis in LCA. SimaPro 8 software was applied to assess the life cycle environmental impacts (CML 2) and cumulative energy demand (CED) of the CDI system in this study. The electricity consumption for CDI operation was measured at 1.44 MJ (0.4 kWh), whereas its total cumulative energy demand was estimated about 23.9 MJ for producing 1 m3 of desalinated water. Results from the impact assessment of CDI revealed a lower global warming potential (GMP100) at 1.43 kg CO2 eq, which was mainly attributed to the major reduction in electricity consumption, as compared to conventional energy-intensive desalination technologies. Moreover, the utilization of material and chemical were shown to be significant contributors to overall environmental impacts in the CDI system (rather than electricity consumption), particularly for the usage of N,N-dimethylacetamide (solvent) and titanium (material for current collector). Use of chemicals might release derivatives that generated adverse impacts in ozone depletion and acidification potentials. This suggests that future studies in CDI design may move forward to substitute or reduce the two to improve the overall environmental performances of the system.