The Untapped Potential of Fog Harvesting

by Torrey Douglass

With the exception of the air we breathe, there is nothing we need more than fresh, clean water. It’s why populations are concentrated along the coasts, lakes, and rivers. It’s why farmers keep an eagle eye on the weather and why squabbles over water rights can devolve into vicious litigation. And it’s also why some people look at an encroaching fogbank, and, instead of seeing a cause for cancelling picnic plans or postponing that hot air balloon flight, they see a water tap that can be turned on with the right tools.

The concept of collecting water out of the air through condensation is not new. For over 2,000 years, people have used water from fog for consumption and other human needs like irrigation, washing, and livestock care. The Incas used stone walls that captured and directed water into irrigation channels, and domed stone structures perforated with tiny openings served as “air wells” in deserts in the Middle East.

In more recent decades, a number of companies and organizations have looked to fog harvesting as a method for bringing potable water to communities plagued by water scarcity. FogQuest, a Canadian nonprofit, has installed fog collection projects in a number of countries including Nepal, Morroco, Guatemala, Eritrea, and Chile, among others. In 1992, FogQuest installed its first system comprised of 100 fog collectors—metal frames with 50 square meters of fine netting stretched within each—on a foggy ridge site in Chile called El Tofo. Fog blown through the netting left behind droplets that slid down into piping that carried the water seven kilometers away to storage tanks in Chungungo, a village on the coast. Over the next ten years, the collectors fed water to Chungungo, and its population doubled over the same time period. On a day without fog, the system did not produce any water, but on the days with the heaviest fog, over 100,000 liters (26,417 gallons) of water were sent down the mountain for Chungungo’s citizens—an average of three liters per day per square meter of netting.

Chungungo is not far from Lima, a city that receives an average of just six millimeters of precipitation annually. In such exceptionally dry conditions, the fog harvesting system was a relatively low-cost and effective way to provide water for the community. It could have continued for another ten years and more if local politicians had not begun advocating for alternative water solutions (like a $1M desalination plant) around 2000. In an attempt to demonstrate the need for government investment, the fog harvesters were allowed to fall into disrepair, becoming completely non-operational by 2003. No alternative system was built, and today Chungungo has (again) resorted to the pricey strategy of trucking in water for its people.

The project at El Tofo demonstrated both the potential and the vulnerabilities of fog harvesting. Yes, the system can pull potable water out of the air, but it needs the right conditions environmentally—significant fog with enough wind to push it through the mesh—as well as culturally. Other projects have reported how lack of community buy-in can lead to inattentive infrastructure maintenance and the system’s ultimate failure. So working with the people the system serves, and designing it to integrate effectively into the local customs, is critical for its longevity.

The Warka Water nonprofit puts this wisdom into practice, consistently integrating local expertise, materials, and building methods into its projects. Founded by Italian artist, designer, and architect Arturo Vittori, the nonprofit looks to both old traditions and new advancements to develop sustainable, culturally appropriately solutions for challenges faced in remote and undeveloped areas. Its water tower, a bamboo frame covered in netting, was designed to be rugged enough to endure the elements while also light enough to be replicated without the need for heavy equipment. Vittori has taken the additional and admirable step of making his designs open source, so anyone motivated to do so can create their own Warka Water Tower, adapting it to their particular geographic and cultural context.

The tower, as well as Vittori’s nonprofit, is named after the Warka tree, a large fig tree found in Ethiopia whose ample shade and abundant fruit make it a gathering hub and highly valued resource for a community. In 2015, Warka Water helped a community in Ethiopia install their own tower. Its organic shape resembles a pillar that gracefully narrows upward with a slight flare at the top. The round nature of the tower facilitates fog collection regardless of the wind’s direction. It is designed to collect not just water, but also precipitation and even the condensation that occurs in the evenings and mornings as the temperature change releases moisture from the air. The footprint is small—the diameter of a mature redwood—and it costs less than $1,000. With the whole community on hand to contribute, it goes up in less than a day, and it is constructed with local, biodegradable materials. Once it is up and functioning, the tower collects 100 liters (26 gallons) of water every day.

The work of Vittori and others exploring fog harvesting comes none too soon, as climate change ejects weather and precipitation out of their once-predictable patterns. Researchers continue to experiment with different netting materials, configurations, and coatings to optimize collection. A team at MIT even used an ion emitter to give fog droplets an electric charge that impells them toward a wire mesh, much like how a magnet attracts iron filings. With this approach, the mesh collects significantly more droplets, which are then gathered into a channel that carries the collected water to storage.

I live in the hills of Anderson Valley, and our home sits above a small vale where fog floats by on misty mornings, sometimes layered and light as ribbons of taffeta, other times dense as a wall of cotton. Motivated by California’s ongoing drought conditions and the very real need to find alternative sources of fresh water besides our wells and waterways, I assembled two types of fog catchers. One uses a large filter pad used in AC units, and the other uses vertical fishing line stretched between two threaded rods. The filter pad is an affordable equivalent to the raschel mesh used by FogQuest and other fog harvesting engineers (raschel mesh can be purchased at BaysideFogCollectors.com). The fishing line approach mimics the Baleen found in the mouths of some whales, a profusion of snugly positioned and bristly plates that sift plankton from the water they suck in. Both designs use 1-½” PVC piping for the structures. Instructions follow if you would like to make your own.

At the time of this writing, the fog catchers have yet to be tested and compared. Due to their size, they are only appropriate for smaller applications, like positioning near a tree or garden bed that would benefit from fog-gleaned irrigation. Yet even small fog catchers can help take a little pressure off your current water sources, and the experience of building one can lead to insights that improve the next project, with the potential for scaling up as designs are increasingly optimized.

Only part of Mendocino County is coastline, but all areas experience fog and morning dew on the grass. Drinking fog is, after all, how our famous redwoods slake their thirst. Our future depends on us staying calm in the midst of crisis, and combining creativity, adaptability, and practicality to find new methods for addressing perpetual human needs. We would do well to mimic the redwoods. Perhaps Mendocino folks of tomorrow will toast to wellness and resilience with a tall glass of fog.

Build Your Own Baleen Fog Collector

MATERIALS

(2) 3’ lengths of 1½” PVC pipe
(1) 32” length of 1½” PVC pipe
(2) 90° 1½” PVC elbows
(2) 1½” PVC T-pieces
(4) 9” lengths 1½” PVC
(4) end caps for 1½” PVC
(2) 3’ long threaded metal rods ½” diameter
1000 yds of 3mm fishing line
(2) long U bolts with 1½” bend
(1) 33” length of gutter

INSTRUCTIONS

Drill two 3/4” holes into each of the 3’ lengths of pipe, one 2” from the top and the other, along the same axis, 24” from the top. Attach the elbow pieces to the top of the 3’ lengths and lay them on the floor 3’ apart with the holes facing each other. Place the rods into the drilled holes and the 32” pipe into the elbow on the left side, doing the same on the right to create a U shape. Attach the T-pieces to the bottoms, perpendicular to the top bar. Add two 9” lengths to each T-piece, adding a cap piece to each end. This completes the main structure.

This next step will take a while. Tie the fishing line to the bottom of the rod on one side, and proceed to thread it up and around the top rod then down and around the bottom, using the grooves of the threads to hold each section in place. When you reach the end, tie off the line so it is secure and as taut as possible. Slide the U-bolts onto the side pieces of pipe about 4” from the bottom rod, with one side slightly lower. If the bolts are not snug, screw a small screw into the pipe just below them to prevent sliding. Place a gutter so it is resting on the U-bolts, and push it all the way to the pipe on the higher side to allow it to angle down toward the low side, leaving a small gap. Install the collector in a location that experiences regular fog, facing directly into the wind for best results. Place a vessel under the gutter to collect your fog water.

Photos, top left to right: close up of fishing line stretched over threaded rod; and materials for the baleen fog catcher; the air filter used in the mesh fog catcher. Next row, left to right: the baleen fog catcher; the mesh fog catcher; and materials for the mesh fog catcher.

Build Your Own Mesh Fog Collector

MATERIALS

(3) 3’ lengths of 1½” PVC pipe
(2) 90° 1½” PVC elbows
(2) 1½” PVC T-pieces
(4) 9” lengths 1½” PVC
(4) end caps for 1½” PVC
(1) 20” x 30” air cleaning filter
(16) zip ties
(2) long U bolts with 1½” bend
(1) 33” length of gutter

INSTRUCTIONS

Using the elbow pieces, attach the 3 lengths of PVC pipe into a U shape. Attach the T-pieces to the bottom of the U, perpendicular to the top bar. Add two 9” lengths to each T-piece, adding a cap piece to each end. This completes the main structure.

Using the zip ties, attach the filter mesh to the structure, hanging first from the top bar and then securing to the sides. Slide the U-bolts onto the side pieces of pipe about 4” from the bottom of the filter, with one side slightly lower. If the bolts are not snug, screw a small screw into the pipe just below them to prevent sliding. Place a gutter so it is resting on the U-bolts, and push it all the way to the pipe on the higher side to allow it to angle down toward the low side, leaving a small gap. Install the collector in a location that experiences regular fog, facing directly into the wind for best results. Place a vessel under the gutter to collect your fog water.

*This photo of fog harvesting equipment in Chile does not depict a FogQuest project, though it shows the same type of system used. For photos and information about FogQuest, visit FogQuest.org.

main photo by Debra Eloise. p18 cobweb photo by Norbert Velescu courtesy of Unsplash; fog catchers image Atrapanieblas en Alto Patache by Nicole Saffie, Pontificia Universidad Católica de Chile, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons. redwood branch photo by Jeremy Bezanger courtesy of Unsplash.

Torrey Douglass is a web and graphic designer living in Boonville and the art director for Word of Mouth magazine.