Long seen as a high-cost, energy-intensive process, desalination mega-projects are seeking to tap renewable resources to limit the cost and environmental concerns of this crucial technology. In June 2022 ENOWA, the energy, water and hydrogen subsidiary of Saudi Arabia's NEOM mega-project, signed a memorandum of understanding with French energy company Veolia and Japanese trading company Itochu to develop a reverse osmosis (RO) water desalination facility powered by 100% renewable energy. Slated for completion in 2025, the facility is expected to produce 500,000 cu metres of potable water per day, meeting 30% of NEOM's anticipated water demand.
In a similar push for zero-carbon desalination, in September 2022 the Dubai Electricity and Water Authority (DEWA) signed a partnership with Dutch start-up Desolenator to develop a solar-powered desalination pilot project.
The companies have already installed a pilot plant at the Jebel Ali power plant and desalination complex, which produces 1000 litres per day, and project the new technology could push the cost of desalinated water as low as $0.02 per litre. Although desalination costs vary considerably based on water source, technology and electricity prices, the average range globally is between $0.50 and $1.50 per cu metre.
DEWA aims to produce 100% of its desalinated water supply from a mixture of renewables and waste heat by 2030.
Over half of the global population suffers from some form of water scarcity every year, and, according to the UN Environment Programme, water supply could fall 40% short of demand by 2030 if no changes are made to water-management systems.
As the costs associated with desalination decrease, the process is likely to play a pivotal role in meeting the UN's Sustainable Development Goal 6, which aims to "ensure availability and sustainable management of water and sanitation for all".
Desalination is already a widespread practice, with approximately 16,000 plants operating in 177 countries. As of 2016 the Middle East and North Africa (MENA) region accounted for 46.7% of the world's desalination capacity, followed by the Asia-Pacific region (17.5%) and North America (12.9%).
Some island countries, such as the Bahamas or the Maldives, are fully reliant on desalination. Limited freshwater reserves and access to plentiful energy reserves have fuelled desalination investment in MENA, especially within the GCC. Approximately half of Saudi Arabia's annual water demand is met through desalination.
Desalination capacity in the Asia-Pacific region is expected to grow significantly, spearheaded by China. With one of the lowest water resources per capita rates in the world, at around 2000 cu metres, China is investing in a five-year plan to raise capacity to 2.9m tonnes a day.
The country's struggle with water scarcity was highlighted when this year's drought challenged China's significant hydropower infrastructure.
Egypt has also made major strides to expand renewables-powered desalination capacity. In 2021 the country tendered 17 25-year concessions from its sovereign wealth fund to construct solar-powered desalination plants. The plants themselves will be partially powered by renewables which, in combination with green financing, could lower production costs by an estimated 20-25%.
The government is targeting an installed desalination capacity of 6.4m cu metres per day by 2050, up from 800,000 in 2021.
This expansion is set to diversify the water resources of the Arab world's most populous country beyond the Nile River â which currently meets an estimated 97% of Egypt's water needs â as development on the upstream Grand Ethiopian Renaissance Dam moves ahead.
Desalination should also support the expansion of industrial and residential development further away from the Nile, in line with new urban development plans.
Major strides have been made since the 1970s to lower the cost and energy usage of desalination, mainly through the introduction of membrane-based RO technology. The cost of desalinated water halved between 1980 and 2005, and promises to decrease further with the scaling of new technologies and renewable resources.
While most desalination plants in the MENA region are powered by fossil fuels, the increasing use of renewable energy - coupled with plans for carbon capture and hydrogen production - should help many countries in the region meet their emissions targets.
Solar, in particular, presents a viable and increasingly affordable energy source for plants.
KarmSolar, an Egyptian solar power and utilities company, is constructing a pilot solar-powered desalination plant at Marsa Shagra on the Red Sea coast with a capacity of 200 cu metre per day. According to the company, any unstored excess water supply produced during peak sunlight hours could be used for local construction activities or in hydroponic gardens.
New technologies have the potential to diversify the power sources used in desalination. The US Department of Energy's National Renewable Energy Laboratory is sponsoring the development of a hydraulic and electric RO wave energy converter, a modular device capable of using the kinetic power of waves to generate potable water from seawater.
Meanwhile, Manhat, an Abu Dhabi-based start-up, has developed floating platforms that use sunlight to distil fresh water. In a zero-electricity process similar to the natural water cycle, sunlight evaporates seawater within a greenhouse-like structure, separating fresh water from salt crystals.
While these two technologies have not been deployed at an industrial scale, they could be used to complement conventional and sustainably powered desalination facilities in future.
Another major environmental concern associated with desalination is the production of brine, or wastewater.
Conventional desalination produces approximately 1.5 litres of wastewater concentrate per litre of potable water produced, at twice the salinity of seawater and containing chemicals such as chlorine or copper used in the treatment of equipment.
However, plans to commodify the brine produced in the desalination process could reduce its environmental impact. Treated brine produces high-purity industrial salt, bromine, boron, potassium, gypsum, magnesium and rare metals, many of which can be utilised downstream.
Within the scope of NEOM's planned desalination plant, brine by-products such as sodium hydroxide could potentially serve as feedstock for the project's planned green hydrogen production.
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