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Looking at new technologies for a thirsty planet

Schematics for using solar heating to enable reverse osmoses to separate salt from water producing drinkable water from brackish and sea water. image credit: Berkely Lab

There were an estimated 700 million people on Earth suffering from drinkable water scarcity in 2018 and that figure is expected to grow to 1.8 billion by the end of the next decade. One in four people live in places at high risk of running out of water.

Yet. our blue planet has plenty of water but most of it is either in form of ice (polar caps) or salty. Water distillation

Water desalination production worldwide based on thermal and reverse osmoses. Source: GWI Desal Data & IDA

is thousands of years old but it requires a lot of energy to heat the water to its boiling point. More recently engineers have developed a method to filter the water separating the salt through a membrane (reverse osmoses). This is better in energy terms but still quite expensive (it takes about 15,000 KW to get 4,500 cubic meter of drinkable water), somewhere between 0.5 and 1$ per cubic meter (in 2019 the 0.5$ per cubic meter barrier has been broken).

Now, that cost might seem negligible but you have to compare it to the cost of normal water (that is basically 0) and consider that desalinated water is not just for drinking but for agriculture (and agriculture requires a tremendous amount of water: to grow one apple it takes 70 litre of water, half a kg of chicken requires 2,275 litres of water…).

Desalination plants geography. Notice how Saudi Arabia is the major producer, followed by US (California). Source: Pacific Institute

Researchers at the Berkely Lab have invented a new process to power desalination using solar energy (see graphic). By using direct solar energy they expect to dramatically cut the cost of producing drinkable water (as well as the one to irrigate fields). Rather than applying reverse osmoses their process uses ionic liquid separation through forward osmoses.

Notice, however, that this process is addressing just one part of the cost in producing water, another important factor that is often neglected, is the cost of managing the salt produced. Today, most desalination plants are simply throwing the brine (salt) back in the sea but this is in creasing local salinity adversely affecting the plancton and the whole food chain. Proper disposal of salt is costly and will have to be managed.

As with any technology there are ups and there are down. It is usually quite difficult to find a solution with no strings attached.


About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the Industry Advisory Board within the Future Directions Committee and co-chairs the Digital Reality Initiative. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.