Senegalese President Macky Sall was to symbolically lay the first stone of Senegal’s very first seawater desalination plant in Dakar on Tuesday, May 31. Once built, the site will provide 50,000 m3 of drinking water per day. The cost is high: 137 billion CFA francs (208 million euros), financed by a loan from the Japan International Cooperation Agency (JICA). But this project is supposed to solve the problem of recurrent water cuts in Dakar, and help the country to face the growing risk of lack of water in the region.
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“While the country is already facing water stress, a 30% to 60% increase in water withdrawals is expected by 2035said a World Bank report, published in March. The Dakar region is particularly exposed even though it already concentrates half of the production of the country’s GDP and population”.
40% of the world’s population lacks water
The case of Senegal is far from isolated. The lack of water already affects 40% of the world’s population and is expected to increase with global warming. “These statistics demonstrate that conventional water sources, such as precipitation, snowmelt and river runoff (…) are no longer sufficient to meet human demand in regions where water is scarce”, estimated a study published in 2019 in the journal Science of the Total Environment.
In response, desalination became an option “increasingly viable”, notes the World Bank. The number of factories in the world is estimated at 16,000, compared to 6,000 in 2000. The technology has long been reserved for a handful of high-income countries: Saudi Arabia and Kuwait still concentrate a quarter of the world’s capacities. But the technology is slowly spreading in low-income countries as costs come down.
Drinking water supply
Slightly less than two-thirds of desalinated water in the world is reserved for drinking water supply in cities and 30% for industrial use. The agricultural sector concentrates less than 2% of demand. “This figure is mainly due to the relatively high cost of desalinated water, explains Michelle van Vliet, professor at University Utrecht, in the Netherlands, and co-author of the study. But its use for irrigation is likely to increase if costs go down, especially for the more expensive crops.” This is already the case in Spain, on the Canary Islands, where around 30% of crops are irrigated with desalinated water, underlined the latest IPCC report on adaptation, published last February.
Can we imagine, then, that no one will run out of water in 2050? In practice, the solution is not applicable by all. In a study published in the journal Nature, Chinese researchers pointed out – while 284 major cities in the world could be affected by water shortages by the middle of the century – that desalination could be an effective solution for only half of them. Thus in Lahore (in Pakistan) or in Delhi (in India), two megalopolises at risk, the geographical situation, far from the sea, as well as the cost prevent considering desalination as a credible solution.
Not to mention that this rapid development is not without controversy. The researchers point to a risk of pollution: the production of one liter of desalinated water leads, in parallel, to the formation of one and a half liters of brine (concentrated in salt, chlorine and copper), most often discharged into the sea or in landfills. Some scientists are concerned about the effects of this waste on marine ecosystems. According to estimates, 52 billion cubic meters of brine are already produced each year. Admittedly, treatment techniques exist, but their high cost still makes their adoption prohibitive.
The other concern comes from the large amount of energy consumed by desalination plants. The most recent data dates back to 2012: the International Renewable Energy Agency estimated the amount of energy needed to run the stations at 75 TWh per year. However, only 1% of them were powered by renewable energies. If desalination continues to run on fossil fuels, the carbon dioxide emissions linked to these processes could increase by 180% by 2040 according to calculations by the world organization. Global Clean Water Desalination Alliance. Proof that, as is often the case, when it comes to adapting to global warming, the solutions are not self-evident.
A falling bill
The cost of producing one cubic meter of desalinated water is €1.34 on average, according to the World Bank. By comparison, it was around €10 in the 1970s, then dipped below €5 in the 1990s.
Worldwide, desalination plants produce 95 million cubic meters of drinking water per day, supplying 300 million people.
high-income countries (with a gross national income of more than €11,665 per inhabitant) still concentrate 67% of global capacities.
In six countriesmore than half of the water consumed comes from desalination: Equatorial Guinea, United Arab Emirates, Seychelles, Cape Verde, Oman and Barbados.