Alyssa Gilbert Director of Innovation, Grantham Institute – Climate Change and the Environment, Imperial College London Dragan Tutic Chief Executive Officer and Founder, Oneka Technologies Several arid countries across the Middle East rely on desalination to meet 50-100% of their municipal water demand, including Kuwait, Oman and Saudi Arabia,75 as water scarcity continues to intensify globally. Regenerative desalination is a sustainable approach to water purification that reuses and recycles water and resources within the process, thereby minimizing waste, energy demand and environmental impacts compared to conventional desalination methods. When powered by renewable energy, regenerative desalination systems can further reduce water treatment-related emissions. Together, these advances could make desalination more sustainable, easing pressure on planetary boundaries related to climate change, freshwater use, novel entities and biosphere integrity. Most conventional desalination systems use energy-intensive reverse osmosis (RO), which forces seawater through high-pressure membranes to separate freshwater from salts and produces brine that is discarded through costly and resource- intensive disposal methods.76 In contrast, an emerging regenerative method called electrodialysis with bipolar membranes (EDBM) splits water molecules to produce hydrogen and hydroxide ions, which then combine with salt ions to form usable acids and bases like hydrochloric acid and sodium hydroxide.77 Desalination plants can recover and reuse these chemicals, reducing reliance on external inputs, lowering costs and decreasing the volume and chemical load of brine wastes. When paired with sustainable sources like solar, wind or low-grade waste heat, EDBM can support lower- emission, lower-impact desalination in resource- constrained or remote settings.78 Pilot projects are already demonstrating the feasibility of recovering valuable materials from high-salinity brine. For instance, a semi-industrial site in Southern Europe processed seawater brine into hydrochloric acid and sodium hydroxide using EDBM, achieving product purities above 90%.79 On Lampedusa Island, an integrated system combining nanofiltration, evaporation ponds and EDBM recovered high-purity magnesium and calcium hydroxides while minimizing liquid discharge.80 Start-ups like Desolenator are using solar energy or industrial waste heat to power circular desalination without emitting any greenhouse gases during operations and fully eliminating toxic brine disposal,81 or using wave energy like Oneka to desalinate seawater in a sustainable and emission- free way without any emissions or chemicals. This can be combined with lower salinity, highly diluted brine or be used as artificial reefs for marine life.82 Other pilots are exploring brine reuse in aquaculture, algae cultivation and constructed wetlands – using the minerals in brine to support plant and animal growth or restore natural habitats. As regenerative desalination technologies advance, they could ease pressure on several key planetary boundaries, reshape industrial water use, generate usable outputs and expand water access. By drawing power from renewables rather than fossil fuels, regenerative systems support the climate change boundary. Recovering chemicals from brine reduces harmful discharges, helping address biosphere integrity and the spread of novel entities. With a projected 40% gap between freshwater supply and demand by 2030,83 sustainable seawater treatment could help ease pressure on freshwater resources, alongside urgent alternative solutions, which are also needed to ensure reliable supply. However, costs remain high, and renewable energy used for desalination could compete with other needs – especially in energy-constrained regions.84 Further, despite promising pilot results, widespread deployment may take a decade or more due to high energy demands, uncertain markets for recovered materials and limited policy support.85,86 Economically, adoption could create new roles in membrane engineering, chemical recovery, decentralized water treatment and environmental monitoring. Modelling studies of hybrid RO-BMED (bipolar membrane electrodialysis) systems suggest potential cost reductions of up to 25% compared to standalone desalination, assuming high-value acid and base recovery.87 However, these systems remain at early-stage or modelled scale, and most experts agree that broader deployment depends on membrane advances, co-product markets and policy support – factors that could take a decade or more to align. With proper technical configurations and local investment, regenerative approaches could reduce the environmental trade-offs of desalination while expanding access to freshwater. Pilot projects are already demonstrating the feasibility of recovering valuable materials from high-salinity brine. 10 Emerging Technology Solutions for Planetary Health 32

10 Emerging Technology Solutions for Planetary Health 2025