Deduction of carbon footprint for membrane desalination processes towards carbon neutrality: A case study on electrodeionization for ultrapure water preparation

Decarbonization of the industrial sector, especially in power generation, is vital for achieving carbon neutrality. The life-cycle greenhouse gas (GHG) emissions, namely carbon footprint, of a technology under the decarbonizing macro-environment should be deduced to reveal further opportunities for GHG reduction. Herein, a case study on ultrapure water (UPW) preparation by electrodeionization (EDI) was investigated through life cycle assessment (LCA) and compared with a conventional mixed-bed ion exchange (MBIX) technology. The carbon footprint of the EDI process was quantified as 1.30 kg CO2-eq/metric ton UPW, which is 27.73 % lower than the MBIX. With a decarbonized power grid and recycling of wasted EDI modules, the carbon footprint will be reduced by 91 %. Meanwhile, the proportion of module production and waste management will increase to 18 %. Thus, we suggest reducing the process energy consumption and improving the current efficiency of the EDI process by process modeling and optimization. With the decarbonization of electricity, the degraded reuse of plastic and the recycling of ion-exchange membranes and resins could be considered. The application of LCA to quantify the carbon footprint and provide suggestions for low-carbon designs could be extended to membrane desalination or industrial processes, supporting the revolution towards carbon neutrality.