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How to harvest water from clouds of fog
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LAARE, Kenya – Jacob Murungi and his wife don't sleep much. Instead, they spend their nights in the local forest high in the mountains of central Kenya collecting water — from the trees.
"I'm out here all night, carrying full water containers to the house, putting empty ones out," he says in Swahili.
It's early morning, and Murungi is standing next to a towering tree. At its base rests a large yellow plastic jerrycan. A plastic sheet — discarded packaging taken from the trash and cleaned — is pinned to the bark of the tree using thorns from a nearby plant and then tucked into the jerrycan.
"At night when the mist comes, water forms on the tree. Then it rolls down the trunk, onto the plastic and into this container," he explains, tapping the jerrycan.
This September morning, the air is cool. Murungi's wearing a wool hat and a maroon fleece, long pants and tall rubber boots. But the sun — strong at the equator — will soon warm the area. When the ground heats up during the day, its moisture evaporates into the air. Then when the night brings cooler temperatures, that moisture condenses, forming a fog of water droplets that Murungi and his wife collect.
Finding water in many parts of Kenya is a struggle. The country is in the midst of its worst drought in decades. Rivers are drying up and the rainy season, once certain, has repeatedly failed to produce significant rainfall. Around the world, climate change is worsening drought conditions and limiting water access, leaving people searching for surprising sources, like fog and dew.
And while some of the methods for fog harvesting, like this one in the mountains, have been around for generations, scientists and entrepreneurs have been innovating new ways, including technology that can pull water from the air in practically any environment.
'Poverty taught us this'
Murungi says on an average night, one tree can fill five jerrycans (more than 20 gallons) with this method. He says everyone in their small village gets water this way.
"Look around," he says. "They're everywhere."
All around the forest, jerrycans and plastic sheets seem to sprout from the trees.
Murungi takes a jug with some of that morning's haul across the street to their small house. He's a farmer and needs to get water to his two cows, who graze outside amid more empty plastic cans.
His wife, Rudia Nyuroka, takes a break from planting yams. She says the water from the trees covers all their household needs – cleaning, cooking, bathing, water for the animals and drinking (after they boil it).
Asked who taught them to harvest the fog like this, she smiles wryly.
"Poverty," she says in the local Meru language with a small laugh. "Poverty taught us this."
The couple has been doing this for decades, starting when their now-grown children were babies. Their parents did it, too, using banana leaves and metal pots before plastic was available. Fog harvesting is traditional here – and in other parts of the world. And it's becoming increasingly crucial.
A method that mimics nature
If the couple didn't have the trees, the closest source of water is about a mile's walk down a steep hill to a school where there are water taps. They also collect rainwater, but fog is more reliable and the rains rarely come.
"Water really is the first way that climate change is being experienced," says Rachael McDonnell, deputy director general for research at the International Water Management Institute.
McDonnell says this idea of taking water from the air is not new, but as humans look for more sources, there's an increasing amount of development happening with it.
"It's fascinating how it's becoming a little bit more mainstream," McDonnell says. "These are traditional techniques, and they are being expanded."
Most fog harvesting operations around the world use big mesh nets to trap the fog, which condenses into water and drains into collection buckets. Scientists and universities around the world, including Kenya, are trying to find the best material and structure for nets, and working to improve the method.
"Of course, this is just mimicking nature. The plants that we see in our desert. They grow little hair, little outgrowths, that as the moist air comes, it traps it," McDonnell says. "Nature does it best, always. But we're learning to harness it for some of the uses that we as humans need."
In the last decade or so, fog harvesting projects have sprouted up in Morocco, Chile, Yemen, Ethiopia and across Southeast Asia, especially near coasts where water-drenched air is moved by the wind.
And McDonnell points out – there's no energy involved. The carbon footprint is essentially nothing. There is one problem, though: Fog isn't necessarily a constant. And it, too, is affected by climate change.
"It depends how long the fogs are available for. Is it a season? Is it three months?" she says.
Like magic
Getting water from fog isn't the only way to harvest from the air. New technology has made it possible to pull atmospheric water from practically any environment, taking the reliability of fog out of the equation. It uses fans to suck in hot, moisture-filled air and then cools the air to condense the water – much like a dehumidifier or an AC unit. The water is then filtered and minerals are added, making it safe for drinking.
This technology has been developed in several places around the world, including Kenya. One place it's being used: Kibera, the biggest slum in the capital city of Nairobi.
Tucked into the winding alleyways of dirt roads and corrugated steel is Saint Juliet's Primary School, with around 500 students from first to eighth grade. During morning break, two young girls walk down a set of wooden stairs carrying a bright green plastic pitcher.
Outside, a boxy machine sits inside a metal cage. Beneath it is a tap. One of the girls puts the pitcher down and turns the tap, filling up the pitcher with fresh, clean water in seconds. Their teacher Chris Musonye stands nearby.
"Before we had this system, it was challenging," he says. "We would waste a lot of time running up and down looking for water."
The taps in Kibera, managed by the city, often run dry. Musonye says right now, they've been off for three months. That's led the price of water being sold at kiosks in the slum to quadruple, meaning most kids simply can't afford it.
"They would spend the entire day thirsty," he says. "But since we got this machine, the kids can be able to at least get enough water to drink."
That machine, called Majik Water, was developed by Beth Koigi, a 32-year-old Kenyan woman.
A decentralized water source
Koigi grew up in a water-rich area north of Nairobi, but she moved to an eastern part of Kenya for college, where water was hard to find. She says it was the first time she had to think about water.
"For me, it was kind of a shock," she remembers. "Every time you have to think, oh, where do I get water for today?"
Then there was a prolonged drought a few years ago, which meant she started seeing similar circumstances all over the country. Even her hometown's rivers dried up. Koigi wanted to figure out a way to create clean drinking water, even when traditional sources were dry. She calls it a "decentralized" water source.
"I wanted to look for ways that you can have a water source – even if you don't have water for anything else, you have clean drinking water," Koigi says. "Because I think you can survive without taking a shower, but you can't survive without water for drinking. So that was the whole idea."
Koigi eventually met some like-minded people at a climate conference and together they founded Majik Water to make what they call "atmospheric water generators." It was initially backed by a Kenyan climate incubator, funded in part by the World Bank.
Several years later, Majik Water has a few dozen air-to-water systems around Kenya. Some have been financed by donors (like the one at Saint Juliet's Primary School), others by nongovernmental organizations or private companies. The technology is expensive, costing thousands of dollars for even the most basic model. And it uses energy – often solar powered – so it's not passive in terms of environmental impacts like traditional fog harvesting.
It's for these reasons that Koigi says she wants her system to be seen as a kind of a last resort.
"I just feel like, you know, there isn't one way of solving the water issue. A lot of people are trying to think what is the easiest way to solve the water crisis, but I don't think there's one solution. It's a combination of many," she says.
She says that needs to include environmentally forward policies, community outreach, rethinking water consumption and reducing greenhouse gas emissions.
But part of the solution is exploring all possible water sources – including pulling it right out of thin air.
Copyright 2023 NPR. To see more, visit https://www.npr.org.
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