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Adaptation option

Desalinisation

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 occurs severely and can be exacerbated in the future, also due to climate change. However, desalination is an energy intensive process; to avoid maladaptation it is essential that desalination is done using renewable energy. Moreover, desalination produces a by-product, brine (a concentrated salt solution) that must be properly disposed of to avoid adverse impacts on the marine environment. So desalination should only be applied if other more environmentally sustainable options (e.g. Water restrictions and water rationing, Water reuse) are not available or cannot be implemented. 

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 (SWRO). Feed water is forced though the rolled up membrane under high pressure. Other electrically driven technologies include Mechanical Vapour Compression (MVC) and Electrical Dialysis (EDR). 
  • Thermally driven technologies; the thermal desalination process uses energy to evaporate water and subsequently condense it again. Thermally driven technologies include: multistage flash distillation (MSF), multi effect distillation (MED), thermal Vapour Compression (TVC) and Membrane Distillation (MD).  

There are currently around 16,000 desalination plants worldwide, with a total global operating capacity of roughly 95.37 million m3/day and brine production of 141.5 million m3/day. Currently, desalination is largely used in the Middle East and North Africa (70% of global capacity), in the US, increasingly in Asia, and only to a limited extent in Europe (about 10% of global capacity). Several southern EU countries are however using desalination to help cover freshwater needs (Jones et al., 2019). 

In the EU, a small fraction of freshwater is obtained through seawater desalination. EU facilities can supply up to 2.89 billion m3 of desalted water a year (active capacity). 71% of the water produced is used for public water supply (2 billion m3, 4.2% of total water employed in public supply). 17% of the desalinated water produced in the EU is used for industrial applications, 4% in power plants, and 8% for irrigation. EU desalination plants are mainly located in Mediterranean countries, where they will be mostly needed in the future: about 1,200 plants provide a capacity of 2.37 billion m3 (82% of total EU desalination capacity) (Magagna et al, 2019). 

Additional Details
Reference information

Adaptation Details

IPCC categories

Structural and physical: Technological options

Stakeholder participation

According to the EU legislation, in the absence of mandatory EIA there is no formal consultation process for the construction of a desalination plant. At the level of countries, stakeholder engagement in desalination projects can be required by the specific national legislation in place or activated through informal processes, e.g. to co-identify the best location of a plant.

Success and Limiting Factors

Desalination is still the most energy-intensive water treatment method and to avoid maladaptation it needs to be combined with the use of renewable sources of energy and increasing efficiency in energy use. 

The electricity requirements vary according to the desalination technology, the salinity of the water source and the desired level of purity of the desalted water at the end of the treatment. In general, membrane desalination technologies such as reverse osmosis (RO) have lower energy requirements than thermal technologies such as multi stage flash (MSF). MSF systems require roughly 83-84 kWh/m3 of energy, while large scale RO systems require 3-5 kWh/ m3 for saline water and 0.5-2.6 kWh/m3 for brackish water (Olsson, 2012 in Magagna et al, 2019). As a result, operating costs are high. The International Energy Agency has estimated that at global level, the energy consumption of desalination is expected to increase eight-fold by 2040, due to increased demand for freshwater (International Energy Agency, 2016). 

Research is focusing on increasing the energy efficiency of the desalination process and on increasing the use of clean energy. Practices combining desalination with renewable energies include: 

  • Combination of desalination and thermal power generation, where waste heat from the power plant is used as heat source for the desalination process. 
  • Solar-driven desalination; this option is especially suited for drier and sunnier regions, such as the Middle East, Northern Africa and Mediterranean Europe. In July 1988, the first solar multi-effect distillation system was put in place at the Plataforma Solar de Almería, a solar research centre located in south-eastern Spain (García-Rodríguez and Gómez-Camacho, 2001).  
  • Wind-powered desalination; for example in the Greek island of Milos, where a wind-based desalination unit has been operating since 2007. The unit has a capacity of 3,000 m3/day.  
  • Desalination plants powered with sea-generated energy; a wave-powered desalination system is for example planned for Cape Verde, off the west coast of Africa. The developer claims the so-called Wave20 plant will produce drinking water at a third of the price of conventional systems. 
  • Desalination plants using geothermal energy; this energy source can generate electricity and heat, making it suitable for both thermal desalination and reverse osmosis. A project in Milos island (Greece), proved the viability of geothermal energy for desalination, producing 1,920 m3/day of fresh water for the local community at very low costs. 

Brine discharge can negatively impact on local marine ecosystems as it increases salinity levels in seawater. Brine produced by the desalination process contains chemicals used during the pre-treatment phase. As brine is heavier than normal seawater, it accumulates on the seafloor, threatening species which are sensitive to the level of salinity. (EEA, 2012). Research is investigating the best way to solve or minimise environmental problems caused by brine discharge and management. For example, the LIFE ZELDA project demonstrated the technical and economic feasibility of brine management strategies based on the use of electrodialysis metathesis (EDM) and valuable compound recovery processes with the final aim of reaching a zero liquid discharge (ZLD) process. Brine can also be converted to chemicals that can be re-used in the desalination process itself (Kumar et al., 2019). 

Costs and Benefits

The main drivers of costs are the used technology, energy cost, plant size and configuration, quality of feedwater and of desalinised water, and environmental compliance requirements. Most of these factors are site-specific in nature. Costs of conveyance and distribution of water are also important, and there are cost advantages for plants located near the coast and on low-lying land (due to lower energy needs for transport upwards; a 100-meter vertical lift is about as costly as a 100-kilometer horizontal transport). 

Overall, thermal desalination technologies, particularly MSF plants, are more capital-intensive than SWRO. However maintaining and operating costs for SWRO plants for each unit of output are double than those of MSF plants, and three times than those of MED plants. For both technologies, but particularly for thermal plants, energy is far and away the largest single item of recurrent cost. The quality of the source water (such as salinity, temperature, and biofouling elements) affects costs, performance, and durability, but also the water quality that can be achieved through the desalination process. 

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 measures, 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, if it is not powered with renewable energy. The EU aims to be climate-neutral by 2050 – an economy with net-zero greenhouse gas emissions. This objective is at the heart of the European Green Deal and in line with the EU’s commitment to global climate action under the Paris Agreement. This will require a shift towards renewable energy driven desalination plants with a higher energy efficiency.  

Implementation Time

Implementation time of desalination plants typically ranges between 3 and 6 years including all phases from planning to operational. 

Life Time

The lifetime is variable and depends on the used technology; for examples membranes need to be replaced every 2-3 years.

Reference information

References:

Magagna D., et al., (2019). Water – Energy nexus in Europe. Publications Office of the European Union, Luxembourg 

International Energy Agency, (2016). Water energy nexus. OECD/IEA 

World Bank, (2019). The role of desalination in an increasingly water-scarce world. World Bank, Washington, DC 

Jones E., (2019). The state of desalination and brine production: a global outlook. Science of the Total Environment, 657, pp. 1343-1356 

EEA, (2012). Towards efficient use of water resources in Europe. EEA Report No 1/2012 

Published in Climate-ADAPT Sep 03 2016   -   Last Modified in Climate-ADAPT May 17 2024

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