Can we produce drinking water without leaving a carbon footprint?

Bordered by the sea on its east and west coasts, the parched landscape of Saudi Arabia is one of the hottest and driest places on earth. The lines “Water, water everywhere, Not a drop to drink” come to mind when you think of the challenges facing this nation.

The capital Riyadh averages just three inches a year, and some pockets of the country may not see rain for a decade or more. In summer, temperatures within its cities regularly exceed 40C, rising to 55C out in the desert. There are no lakes or rivers in the country, and its underground aquifers are rapidly depleting.

Needless to say, Saudi Arabia understands the value of water all too well.

But unlike the lost and desperate sailors in Coleridge’s famous poem, “Rime of the Ancient Mariner”, Saudi scientists have taken advantage of the salty sea around them through desalination. Now, as the world’s largest producer of desalinated water, they are moving towards a future where this essential resource is affordable and sustainable.

Zero carbon desalination

Traditionally, desalination has been achieved through distillation, where seawater is heated to separate the potable liquid from salt and other contaminants. The process is not only energy intensive but also expensive.

But this all changed in 2016, when Crown Prince Mohammed bin Salman announced Vision 2030, a strategic plan that sought to improve life in all parts of Saudi society. It included several sustainability commitments – such as increasing energy from renewable sources and reducing carbon emissions – which are now part of the Saudi Green Initiative.

The trickle down effect was visible everywhere, but especially in the country’s water industry. Leading the charge was the Saltwater Conversion Corporation (SWCC), the corporation that produces about 70 percent of the Kingdom’s desalinated water.

The SWCC launched a program to replace thermal distillation technology at its plants with reverse osmosis, a more energy-efficient process that forces salty water through fine membrane filters. Compared to distillation, this method typically uses only a quarter of the energy to produce the same amount of water, according to the SWCC.

The corporation has also introduced newer membrane filtration technology – developed by scientists based in Saudi Arabia – to halve the amount of energy used according to SWCC consulting engineer Nikolay Voutchkov. It’s so efficient, the SWCC set a new Guinness World Record in March 2021, for the lowest energy water desalination plant in the world.

“Despite our achievements so far, we still have the drive to do better,” says Voutchkov.

The SWCC has now set goals to halve its energy consumption by 2030 and be carbon neutral by 2050. Much of this change will come from further improvements in technologies used in the plants, says Voutchkov . These include improved membrane filtration systems, new energy recovery devices that will reduce waste to almost zero, and more energy efficient pumps, all of which will contribute to a reduction in the use of fossil fuels.

The SWCC also plans to introduce more extensive carbon capture and storage processes into its distillation processes and introduce an extensive tree planting program across its sites to encourage further CO sequestration.2 emissions.

Their desalination plants are also being made smarter. With the help of AI systems, machines are able to automatically maximize their energy and chemical use when producing water, says Voutchkov.

Perhaps some of those carbon emissions could also be saved by harnessing the power of the sun – something scientists at Saudi Arabia’s King Abdullah University of Science and Technology (Kaust) are investigating.

One futuristic proposal under consideration is a “solar dome”, which will focus the sun’s heat to evaporate seawater and produce fresh water. Similar types of technology are already being used to produce electricity through steam power, but if scientists deem it viable for full-scale implementation, this will be the first time it has been used for desalination.

Researcher working at the Desalination Technology Research Institute (DTRI)

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Researcher working at the Desalination Technology Research Institute (DTRI)

(SWCC)

But Kaust has already built more realistic prototypes. In one, desalination equipment was combined with solar panels so that the heat generated by these panels could help evaporate the seawater. Tests have shown that it can produce as much as 1.64l of water per square meter of solar panel surface every hour and that water for use in farming does not require additional treatment.

Turning seawater into a resource

Desalination – even of the low-energy reverse osmosis type – comes with another challenge: salt water. This by-product has the potential to affect coastal life and ecology, as some desalination plants release it back into the sea. In fact, as a country with no lakes or rivers, Saudi Arabia is the largest producer of brine in the world.

Again, Voutchkov has an ambitious plan: to turn the by-product into a resource. “The desalination industry is often challenged with the impact of brine spills into the marine environment,” he explains. “However, the reality is that the desalination industry and regulators today have a comprehensive system to predict, monitor and control the potential environmental impact during all stages of project development and operation .”

In Saudi Arabia, the discharge from desalination plants is continuously monitored to ensure that the marine environment is preserved and protected, and that all waste is treated to an environmentally safe standard, according to Voutchkov.

He also says that brine is rich in minerals, including sodium chloride, magnesium and rubidium, and the extraction of these valuable resources could form the basis of a whole new industrial chain.

“The commercial proceeds have the potential to fully subsidize the cost of water production in Saudi Arabia, as well as lead us towards new sources of renewable energy for the Kingdom,” he says.

Plans are already underway to build a new treatment plant in the Kingdom that will act as a “brine mine”, where minerals and rare metals will be extracted from the brine. Sodium chloride, for example, will then be sold to local chlor-alkali companies that produce products such as chlorine and caustic soda.

According to Dr. Ahmad Al Amoudi, director of the Institute for Research, Innovation and Desalination Technologies at SWCC, agreements have already been made with several chlor-alkali production companies in Saudi Arabia to deliver these raw materials once the plant is on bottom.

Dr Al Amoudi’s team is also working with the US Department of Energy on a joint research program to look at ways to extract rubidium from seawater for the purposes of producing environmentally safe energy.

Hydrogel technology

In the misty desert of Namibia, where rain is rare and the fauna is thirsty, ingenuity is rewarded. This is why the mist-basking beetle, a creature no bigger than a strawberry, can be seen climbing high dunes and doing handstands. At these water-rich heights, the mist condenses on the beetle’s body and rolls straight into its mouth, completing the successful, magical extraction of water from the air.

At Kaust, researchers are perfecting technology that achieves similarly ingenious results. In 2018, Peng Wang and his team at the university’s Water Desalination and Reuse Center created a hydrogel—a polymer that looks like a black, squishy blob—that can capture water from the air for other uses or even for drinking.

Hydrogel can literally pull water out of thin air

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A hydrogel can literally pull water out of thin air

(Getty)

The hydrogel contains calcium chloride, a non-toxic salt that is particularly thirst-quenching; it absorbs water vapor and moisture from the air, and then releases the liquid when exposed to the right conditions.

In Kaust’s prototype tests, 35g of hydrogel absorbed 37g of water; when left outside in the sunlight for a few hours, the pure water separated from the gel and was collected. The laboratory estimated that collecting 3l of water could cost as little as half a cent per day, which is extremely important for the less affluent regions of the country in the coming years.

The next step was to take the production of water from a batch process to a continuous process – a task that the team achieved in 2019. And in 2020, the team was able to develop a prototype solar panel that was cooled using water from hydrogel, an innovation that is extremely useful in the heat of the Middle East.

Little is known that as temperatures rise, solar panels produce less energy and become more inefficient. In tests, Kaust researchers found that water released by the hydrogel could cool the solar panels by up to 10C, greatly improving their efficiency.

Renyuan Li, the lead researcher on the project, said when announcing the research results: “We believe that this cooling technology can meet the requirements of many applications because water vapor is everywhere and this cooling technology easy to adapt to different scales.

“The technology could be made as small as a few millimeters for electronic devices, hundreds of square meters for a building, or even larger for passive cooling of power plants.”

The future of water

As the effects of climate change increase, resources such as water will only become more valuable, which means that producing it cheaply and sustainably is more important than ever. And the research and innovations already underway in Saudi Arabia could be a model that could be replicated in other water-scarce parts of the world.

As Dr Al Amoudi says: “Water is so important to life and we must protect it for future generations.”

The IS Saudi Green Initiative Saudi Arabia’s whole-of-government approach to tackling climate change.

[The article was originally published in October 2021]

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