To make the water of the oceans usable, it must be desalinated. According to estimates by the International Desalination Association (IDA) and Global Water Intelligence (GWI), there are around 20,000 seawater desalination plants worldwide, with a total capacity of around 100 million cubic metres of water per day.

These desalination plants are mainly located in regions where water is scarce, particularly in the Middle East (about 6,700 units), Asia (4,800 units), North America (3,300 units, particularly in California), South America (1,400 units) and Southern Europe (2,100 units). Of these, 330 plants are located on the Canary Islands alone, supplying the extensive banana plantations and the tourism sector.

According to estimates, the demand for water through desalination could increase to 300–400 million cubic metres of water per day by 2050. The GWI forecast assumes that the capacity required worldwide will double or triple by 2030.

The Middle East and North Africa region could already obtain 70 to 80 per cent of its water resources from desalination by then. India and China are planning to significantly expand their desalination capacities. The same applies to the USA.

Desalination plants, which convert seawater or brackish water into fresh water, are extremely energy-intensive. Energy accounts for around 40 to 50 per cent of operating costs. Depending on the technology used (reverse osmosis or thermal process), the energy requirement per cubic metre of water varies from 3-6 kWh to 15-25 kWh. Many plants cover their high energy needs with fossil fuels and emit large amounts of CO2. The future therefore lies in the use of renewable energies, such as solar and wind energy, as well as hydropower. However, it is difficult to implement on a net-zero basis. The most modern desalination plant in the world to date still relies on 60% fossil energy.

And there is another environmental problem. During the desalination of 100 litres of water, a waste product is produced, highly concentrated brine, which is fed directly back into the water. From 100 litres of salt water, about 45 litres of desalinated water are obtained by desalination and about 55 litres of brine are produced. It pollutes the ecosystem in many ways. It is estimated that by 2023, about 51 billion cubic metres of brine had been washed into the oceans. This corresponds to a salt layer of 15 cm on the area of France.

Many countries have responded to the challenges of water scarcity and the problems associated with desalination by launching research projects. You can find out more about this topic by clicking on the links below.