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Desalination—removing salt from seawater—has emerged as a growing option for supplying drinking water as climate change worsens droughts, disrupts rainfall patterns and contributes to wildfires, according to Associated Press reporting. The basic goal is to create freshwater in places where rainfall, rivers or groundwater cannot reliably meet water demand.
Most modern desalination plants rely on reverse osmosis, a process in which seawater is forced at high pressure through a semi-permeable membrane. The membrane lets water molecules pass while blocking most salts and other impurities, producing freshwater on one side and a highly concentrated salt solution known as brine on the other.
Before the seawater reaches the membrane, plants typically filter it to remove debris and microorganisms that could clog equipment. After reverse osmosis, the freshwater is treated again to meet drinking water standards, which often includes adding minerals.
An older approach, thermal desalination, works differently: it heats seawater until it evaporates, then condenses the vapor back into liquid while leaving salt behind. The AP report said thermal desalination is still used in some regions but is generally more energy intensive than reverse osmosis.
Desalination is used widely beyond the Middle East, and the AP report points to drought-prone coastal areas in the United States—particularly California and Texas—as places where the technology has become more common. In parts of Africa and Australia it is also used, and in some Pacific Island nations where rising seas have contaminated groundwater with salt, desalination is becoming an increasingly important freshwater source.
The report said more than 20,000 desalination plants operate worldwide, and that the industry has expanded at about 7% annually since 2010, citing the International Desalination and Reuse Association. It noted that use is especially significant in the Middle East: Kuwait and Oman, among other countries, source more than 85% of their drinking water from desalination, according to a 2022 report by the French Institute of International Relations.
While desalination can increase freshwater supply, the AP report describes significant trade-offs, starting with energy use. It cited a 2025 study published in the journal Water Research estimating that desalination plants worldwide produce between 500 million and 850 million tons of carbon emissions annually.
The same AP reporting compared that range to an estimate that the entire global aviation industry emits about 880 million tons, according to Air Transport Action Group. The report also said desalination’s byproduct—highly concentrated brine—is typically discharged back into the ocean, where it can harm seafloor habitats and coral reefs by increasing salinity and introducing chemicals used during treatment.
The intake systems that draw water into desalination plants can also trap and kill fish larvae, plankton and other organisms at the base of the marine food web, the report said. Those losses can ripple outward, reducing populations of fish and larger predators that depend on them.
Researchers and companies are pursuing ways to reduce environmental impacts, the AP report said, including powering plants with renewable energy and developing more efficient membrane technology to reduce energy consumption. Some are also experimenting with moving the process into the deep sea, where natural ocean pressure can help drive reverse osmosis and lower the need for additional energy.
The AP report also highlighted that many experts argue water recycling and conservation should come first. It said wastewater purification typically uses far less energy than seawater desalination and can substantially reduce impacts on marine life.