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Desalination: worth its salt in an increasingly water-scarce world

Water scarcity updates

As the world warms up, droughts are set to be more frequent and severe. Given likely population growth, that creates the threat of a liquidity crisis. By 2050, nearly half of the global urban population is projected to live in water-scarce regions.

The world is not short of water. It covers 71 per cent of the earth’s surface. But it is not where it is needed and 97 per cent of it is salty. Desalination is a partial, but increasingly important, solution. Egypt is the latest to embrace it. It is seeking investors to join with its sovereign wealth fund in a $2.5bn desalination project.

As a lower middle-income country, it is in a minority. About 90 per cent of desalination capacity is in high-income countries, as the chart shows. That is partly because they are expensive to erect. Poseidon, a subsidiary of Brookfield Infrastructure Partners, expects to spend $1.4bn on a desalination plant for Orange County in California. The project, opposed by some on ecological grounds, is expected to get the green light by the end of the year after 20 years in the planning.

Desalination plants are also costly because they use a lot of energy to run. Producing water accounted for as much as a fifth of all energy consumption in Saudi Arabia, according to a 2017 research paper.

But that may be changing. More efficient pumps, membranes and energy-recovery devices mean it now uses a quarter of the electricity it did in the 1980s, says Barclays. Moreover, renewable energy is starting to feature more heavily, including in the Egyptian project. The global industry wants to power a fifth of new desalination plants this way between 2020 and 2025.

As well as the falling cost of renewables, there are innovations in design. A concept known as the “Seawater Greenhouse” uses seawater and solar power to create cooler and more humid conditions for greenhouse-cultivated crops in arid regions. There is growing interest in hybrid systems that use concentrated solar power to heat up water and generate electricity to drive pumps, though more work is needed to reduce costs.

Challenges remain, but there is a good case for harnessing the sun to make potable water. The worst water shortages are in sunny climates. All too often, adapting to climate change involves energy-hungry equipment that creates more emissions. Using renewable energy for desalination holds out the promise of breaking that feedback loop.

The Lex team is interested in hearing more from readers. Please tell us what you think of desalination technology in the comments section below.

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