Adaptation option


Desalination is the process of removing salt from sea or brackish water to make it useable for a range of 'fit for use' purposes including drinking. It may thus contribute to adaptation to climate change in all those circumstances in which water scarcity problems may be exacerbated in the future. Desalination produces a by-product, brine (a concentrated salt solution) that must be disposed. Desalination techniques include:

  • Electrically driven technologies: Reverse osmosis is the most frequently used technique: it consists of filtering water with osmosis membranes that separate salt from water. Feed water is forced though the rolled up membrane with high pressure. Other techniques include Mechanical Vapour Compression (MVC) and Electrical Dialysis (EDR)
  • Thermally driven technologies: multistage flash distillation (MSF), multi effect distillation (MED), Thermal Vapour Compression (TVC) and Membrane Distillation (MD).

According to the UN World Water Development report 2014, ‘there are currently more than 16,000 desalination plants worldwide, with a total global operating capacity of roughly 70 million m3/day, and the operating capacity could double by 2020’. Currently, desalination is largely used in the Middle East and North Africa (70% of global capacity), in the US, increasingly in Asia, but to a limited extent in Europe e (10% of global capacity). Several southern EU countries are however using desalination to cover freshwater needs. Spain is the biggest user of desalination with currently 700 desalination plants and a capacity of 1.6 million m3 a day, providing water for 8 million people every day. Other EU Mediterranean countries have much smaller capacities, with some 240 000 m³/day in Italy, 100 000 m3/day in Cyprus and 30 000 m³/day in Greece (EEA, 2012). Desalination is expected to double over the next 50 years in Spain. The United Kingdom has opened in 2010 its first desalination plant in east London, the Thames Water Desalination Plant.

Additional Details
Reference information

Adaptation Details



IPCC categories

Structural and physical: Technological options

Stakeholder participation

In the absence of mandatory EIA there is no formal consultation process for the construction of a desalination plant. Participation levels depend on local legislation.

Success and Limiting Factors

Desalination is very energy intensive: Desalination is an example of conflict between mitigation and adaptation measures, as it is still the most energy intensive water treatment method and as most countries power their desalination plants with fossil fuel. Energy consumption for desalination by reverse osmosis is around 4 kWh per cubic meter; distillation needs about 10kwh per cubic meter. As a result, operating costs are high. Research is focusing on increasing the energy efficiency of the desalination process and increasing the use of clean energy to power the plants, through the development of synergies between power generation and water services. The International Desalination Association has a goal of achieving a 20% energy reduction by 2015 (UN WWDR 2014). Technologies to reduce energy consumption of desalination:

  • Improve energy efficiency of pre-treatment in reverse osmosis
  • Develop forward osmosis technique over reverse osmosis
  • Develop electrodialysis for desalination

Renewable energies and desalination:

  • Combination of desalination and thermal power generation, where waste heat from the power plant is used as heat source for the desalination.
  • Solar-driven desalination:  This option is especially suite for arid regions, such as the Middle East. The project SolarPACES IA, supported by the International Energy Agency, aims to combine, solar energy plants and desalination plants, using the waste heat produced by the solar plant to purify water. In Europe, demonstration projects have been led in Spain (Almeria). A disadvantage of the technique is that seasonal variation affects the performance of the plant, while demand for freshwater can remain constant through the year (UN WWDR 2014).

Wind-powered desalination: In Sydney, Australia, desalination plants are using energy produced by the Capital Wind Farm near Queanbeyan (UN WWDR 2014).

Brine discharge can negatively impact on local marine ecosystems as it increases salinity levels in seawater. Brine and other waste produced by the desalination process contain chemicals used during the pre-treatment phase. As brine is heavier than water, it accumulates on the seafloor, threatening species which are sensitive to the level of salinity (EEA, 2012). An on-going project financed by Life + is testing new desalination technologies minimizing the volume of generated brine. In Barcelona, the brine produced by the desalination plant of Llobregat is diluted in the pure treated water of the nearby wastewater treatment plant at Baix Llobregat before being discharged back into the sea. This technique reduces the negative impact of brine discharges.

Costs and Benefits

Investment and operation costs are still very high, which makes desalination not suited for large water consuming sectors such as agriculture (irrigation) or for consumption at a distance from the plant due to transportation costs (UN WWDR 2014). Similarly, if the technique seems an option in middle or high income region, it is not affordable for poorest regions (UN WWDR 2014). Energy consumption can account for half of the desalination cost, which makes energy savings a very important element to cut the costs of desalination. Desalination is very sensitive to electricity prices. In Spain, a significant increase in energy prices since 2004, combined with low prices of water, made desalination too costly and led to reducing the use of the technology. Many desalination plants in the south of Spain are running below capacities. In general costs have decreased significantly because of technology improvement but are depending on plant size, raw water quality, energy costs and terms of financing.

The Communication "Addressing the challenge of water scarcity and droughts in the European Union" in 2007 and later the Blueprint to Safeguard Europe’s water resources (2012) propose a hierarchy of water measure, considering that alternative water supply through desalination should be used as a last resort once other improvement of efficiency in demand and production have been exhausted. The communication on resource efficiency (COM(2011) 21), aims to create a framework for policies to support the shift towards a resource-efficient and low-carbon economy. Desalination is mentioned as an option that provides a solution to water supply problems but it may increase fossil fuel consumption and greenhouse gas emissions.

There is no clear legal framework for desalination under EU law. An environmental impact assessment is not required for desalination plants under the EIA directive. Impacts of the desalination process, notably the discharge, are not addressed either (PRODES report).

Some desalination plants have already been funded under the EU Regional Development Fund (e.g. Alicante II-ES), and the EU is supporting the construction of desalination plants in third countries (for instance in Gaza).

Implementation Time

5-10 year.

Life Time


Reference information

Fact sheet provided by the OURCOAST II Project

Published in Climate-ADAPT Sep 03 2016   -   Last Modified in Climate-ADAPT Sep 10 2022

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