Around the world, many populations are facing freshwater shortages. In response, new desalination plants are built every year, but they raise a number of questions. Are they compatible with sustainable development?
Every year, global demand for freshwater increases by 1%. Faced with this constant increase, we're now turning to the oceans... to turn salt water into fresh water!
There are two main desalination techniques: the thermal process, which makes salt water drinkable by distillation, and osmosis (now in the majority), which recovers freshwater from the oceans by filtering it through a membrane. These two solutions consume a lot of energy, while 99% of the electricity used worldwide in the twenty thousand or so existing plants is fossil fuel-based (2017 figures).
According to the IFRI report, at least 120 million tonnes of carbon dioxide are emitted every year. If nothing is done to make the process more sustainable, this figure could rise to 280 million tonnes by 2050.
What's more, every day, desalination plants discharge over 140 million cubic meters of brine, a concentrate of warmer, saltier seawater containing numerous chemicals. Saltier and therefore less oxygenated, ocean water captures less CO2. An unsolvable problem for the moment, but one that raises questions.