Droughts are getting worse. Is fog-farming a fix? todayheadline

The city of Alto Hospicio, in Chile’s Atacama Desert, is one of the driest places on Earth. And yet its population of 140,000 continues to balloon, putting mounting pressure on nearby aquifers that haven’t been recharged by rain in 10,000 years. But Alto Hospicio, like so many other coastal cities, is rich in an untapped water resource: fog.

New research finds that by deploying fog collectors — fine mesh stretched between two poles —  in the mountains around Alto Hospicio, the city could harvest an average of 2.5 liters of water per square meter of netting each day. Large fog collectors cost between $1,000 and $4,500 and measure 40 square meters, so just one placed near Alto Hospicio could grab 36,500 liters of water a year without using any electricity, according to a paper published on Thursday in the journal Frontiers in Environmental Science. 

By placing the collectors above town — where the altitude is ideal for exploiting the region’s predictable band of fog — water would flow downhill in pipelines by the power of gravity. So that initial investment for collectors would keep paying liquid dividends year after year. “If you’re pumping water from the underground, you will need a lot of energy,” said Virginia Carter Gamberini, a geographer and assistant professor at Chile’s Universidad Mayor and co-lead author of the paper. “From that perspective, it’s a very cheap technology.”

It’s a simple idea that’s already in use around the world. Fog is just a cloud that touches the ground. Like a puffy cloud higher in the atmosphere, it teems with tiny water droplets that gather in the mesh of a fog collector, dripping into a trough that runs into a tank. Communities across South America, Africa, and Asia have been deploying these collectors, though on very small scales compared to other methods like pumping groundwater.

So why haven’t cities expanded their use? For one, if a region gets rain, that volume of water is much higher than what can be extracted from fog, and communities can store that rainfall in reservoirs. Fog collection also requires constant attention, as the devices can break in fierce winds, requiring repairs.

The economics are tricky, too. Water remains very cheap in places with modern infrastructure, disincentivizing fog collection, said Daniel Fernandez, an environmental scientist at California State University, Monterey Bay who studies the technology but wasn’t involved in the new paper. “They’re going to catch a few gallons, if you’re lucky, in a day,” said Fernandez, who also founded a company that installs collectors. “That’s kind of cool to get that much from fog. But how much is that going to cost you to turn on your tap and get that much?” 

The investment is more enticing where water is scarcer and therefore more expensive, Fernandez said. As climate change makes droughts more intense, communities struggling to get enough water might find the economics make sense. Supplementing aquifers, reservoirs, and other established sources with fog would help a region diversify its water system, in case one of them dries up or gets contaminated. Alto Hospicio can’t just rely on its aquifers, since they’re no longer being replenished by rain. “Without thinking outside the box, including fog harvesting, that solution places a limit on how long human habitation can exist there,” said Michael Kiparsky, director of the Wheeler Water Institute at the University of California, Berkeley, who wasn’t involved in the new paper.

Dense cities, though, may struggle to deploy fog collectors compared to the countryside. “The wind load on a fog collector is like that on the sail of a sailing ship,” said Robert S. Schemenauer, executive director of FogQuest, a Canadian nonprofit that advises on collection projects. “It has to be very strongly anchored. Therefore, placing it on the building could lead to building damage or material ending up on the street below.”

Beyond drinking water, using the fog for hydroponic farming could help Alto Hospicio and other parched communities grow their own food. Gamberini is already doing additional research elsewhere in the Atacama to expand this kind of farming, growing tomatoes, lettuce, and other crops with fog water and bountiful desert sunlight.

Even in the United States, where water is comparatively cheap, gardeners are experimenting with fog collectors. Peter Weiss, an atmospheric chemist at the University of California, Santa Cruz, has been installing them in Pacifica, just south of San Francisco. In the summertime, fog can provide enough water to sustain a home’s established plants without turning on the hose. 

For Weiss’ next project, he wants to bring fog collection to California’s vineyards. “That could be a way to make it more sustainable, less water intensive,” he said. “At first I hated fog because it’s so dreary. But then I started collecting it, and I loved it.”