Why energy use limits the sustainability of desalination

The article discusses the critical role and limitations of desalination as a response to global water scarcity, which affects nearly four billion people annually. Despite Earth being predominantly covered by water, less than one percent is accessible freshwater, driving increased reliance on desalination, especially in drought-prone coastal regions. Desalination, the process of removing salts and contaminants from seawater to produce freshwater, serves as a necessary but costly and energy-intensive solution. Approximately 350 million people depend on desalinated water, highlighting its importance despite environmental and economic drawbacks. Two primary desalination methods dominate: membrane-based reverse osmosis (RO) and thermal desalination. RO forces seawater through semipermeable membranes under high pressure to separate salts, requiring significant energy—up to 10 kWh per cubic meter for seawater—due to the need to overcome osmotic pressure and mechanical membrane limits. Thermal methods, such as multi-stage flash and multi-effect distillation, evaporate water to separate salts but consume even more energy