Recovering water out of thin air
Fog catchers have been providing water to people in dry, mountainous regions for decades. Due to climate change, more regions get drier, pushing the need for this technology.
- Fog collectors are usually made of a large expanse of mesh that intercepts the fog and catches water droplets. The recovered water can be used for drinking and in agriculture.
- A new technology from the Netherlands allows a polymer-coated textile to take in water from the air as temperatures cool down, and to release the water again when temperatures rise.
On the surface, it may seem like Earth is overflowing with water. Around 70% of our planet is covered in saltwater ocean. On a typical day a similar amount of sky is covered by water-droplet filled clouds. Even in the middle of a desert, air holds moisture in the form of water vapour.
Despite this, getting access to fresh water is not always easy. By 2050, the UN estimates that 5 billion people – over half the predicted population – could suffer water shortages because of climate change, pollution, and increased demand.
To tackle this problem, one solution is to take water from air – or rather, from fog.
The way it works is relatively simple. Fog, like a cloud, contains water droplets suspended in air. Fog collectors are usually made of a large expanse of mesh that intercepts the fog and catches those water droplets. As wind pushes the fog through the mesh, these water droplets build up on the mesh and eventually gravity pulls them down to be collected in a trough.
People have been extracting water from fog for decades in remote, arid regions of countries across the world, from Chile in South America to Nepal in South Asia. The largest fog-collection and distribution system in the world was built in 2015 in the Anti-Atlas Mountains in Morocco, by local NGO Dar Si Hmad.
Peter Trautwein, CEO of Munich-based aqualonis, a company which developed the CloudFisher fog collectors used in the Dar Si Hmad project since it was upgraded in 2017, says the technology is a lifeline for people living in areas where water is scarce.
In total, around 1,200 people living across 16 villages on Mount Boutmezguida in the Aït Baamrane area of the Anti-Atlas Mountains use fog water for drinking and in their households. Thirty-one CloudFisher fog collectors provide over five million litres of water to these people each year, meaning they no longer have to trek hours each day to retrieve water from open wells, or worry about dropping groundwater levels due to overuse and climate change “That’s a big revolution in this valley because people start to grow their own gardens, so they live much healthier now,” he says.
In other places fog water has different uses: In the south of Spain it’s used to fight forest fires, and in South America it is often used for agriculture, says Otto Klemm, professor of climatology at the University of Münster, Germany.
But in order to use fog collectors, a region has to fit a specific set of criteria. Fog must be present for large periods of the year, with no rain at the same time. And, of course, there need to be people close by who require water. “That combination is rather rare,” says Klemm.
There are plenty of mountain ranges in Europe, for example, where it would be possible to collect fog water. But in most places there’s no need to go to such lengths – typically, where there is a lot of fog, there is a lot of rain, too. “For example in central Germany there is a mountain range maybe eleven or twelve hundred meters high and there’s a lot of fog at the mountaintops,” he says. “But no one would collect fog for freshwater production because there’s so much rain.”
Perhaps because of these limitations, installing fog water collection systems has until now largely been the work of volunteers and NGOs. But as climate change means droughts are becoming more common, and water scarcity is predicted to be a problem for billions of people by 2050, more people are getting interested in developing new technology to harvest water from air.
One example is Netherlands-based startup Sponsh. Based on work by Catarina Esteves at Eindhoven University of Technology, they have created a polymer-coated textile that takes in water from the air as it cools down, and releases the water again when temperatures rise. It works at humidity levels as low as 70%, compared to 95% required for traditional fog collectors. “When it is cold the polymer arms stand out, and they want to collect water,” says Lourens Boot, CEO of Sponsh. “They make a slight hydrogen bond with the H2O molecules.”
The simplest way to use this textile would be to wrap it around trees or vines to provide water for growing crops like nuts or grapes, says Boot. But if the air temperature wasn’t quite right – in its current formulation, the textile releases water when the temperature reaches 30ºC – or a farmer wanted more control over the release of water, the company also plans to make a system where water is collected in a box and can be fed into an irrigation system.
The technology is still in the early stages. At the moment the company has created material around 50 square centimetres in size and hopes to scale that up to metres by this summer. They are due to run pilot tests using prototypes this year in time to launch the basic version in 2020.
Agriculture accounts for around 70% of global water usage, so finding ways to lessen the strain it puts on the world’s water supply will be helpful in a future where water stress becomes more widespread.
It’s hard to say how climate change will affect typical fog collection projects, like the one in Anti-Atlas Mountains. It might make fog collection harder at certain altitudes but newly possible at others, says Klemm.
Either way, water scarcity is set to affect more people than ever in the coming years. “All the Mediterranean climates in the world, which is California, Australia, South Africa, and our own Mediterranean Europe, will all have that issue,” says Boot.
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