Assessment of carbon footprint and neutrality potential in groundwater desalination: Reverse osmosis versus electrodialysis reversal under fouling scenarios on a volcanic island

Volcanic islands often rely heavily on groundwater, but their geology creates complex water-rock interactions and recurrent salinization, making desalination a critical water management strategy. This study conducts a comparative evaluation of the carbon footprint associated with electrodialysis reversal (EDR) and reverse osmosis (RO) processes, with a specific focus on their application in Tenerife (Canary Islands). Operational data from an existing EDR facility were used as the baseline, while alternative RO plant design parameters were systematically examined. In addition, decarbonization strategies were investigated, with particular attention to the integration of renewable energy sources and the practice of blending feedwater with permeate. Results indicate that the RO process is principally influenced by membrane fouling, which significantly increases energy demand, and consequently, the carbon footprint. This trend persisted until stabilization under severe fouling conditions (flux decline of 20–45 %), at which stage membrane replacement was required. Under the evaluated scenarios, the RO process exhibited a carbon footprint of 0.33–0.45 kgCO₂/m 3 prod , with a reduction of up to 17 % achievable through product blending. Comparable values were determined for the EDR system, although chemical usage represented a larger contribution of the total emissions. The incorporation of a renewable mini-hydroelectric plant had a more pronounced effect on RO process, reducing the carbon footprint to 0.008–0.01 kgCO₂/m 3 prod . • Comparative assessment of RO and EDR for volcanic groundwater desalination. • Silica-induced fouling elevates specific energy demand and carbon footprint in RO. • Chemical consumption represents a major contributor to EDR-related emissions. • Permeate blending mitigates energy requirements and associated CO₂ emissions. • Mini-hydropower integration enables near carbon-neutral desalination operation.