Research on harvesting water from fog

An unusual research project wants to use fog for irrigation, writes Sandi Doughton.

Fog has been billowing inside a small greenhouse on the University of Washington (UW) campus for the past month, but it doesn’t arrive on little cat feet as with the poem Fog. It comes hissing out of highpressure nozzles.

The man-made mist is part of an effort to help slum-dwellers in Peru harvest moisture from the air. With a small grant from the Environmental Protection Agency, UW students and professors are building and testing fog catchers – and hoping to reel in a bigger grant to mount a full-scale operation in Lima.

‘‘It’s like a cold sauna in here,’’ UW ecologist and civil engineer Susan Bolton said, ducking into the plastic ‘‘hoop house,’’ where industrial-grade misters spewed out a cloud of fine water droplets.

A noisy exhaust fan drew the cloud through a drape of black plastic netting. Droplets settled on the mesh, coalesced and trickled into a plastic bucket.

Forty-five minutes into the morning’s first test run, Bolton and graduate student Peter Cromwell emptied the bucket into graduated cylinders to measure the haul: 1212 millilitres.

Wringing water from fog is not a new idea. Almost 2000 years ago, the people of the Canary Islands gathered water that dripped from trees – nature’s own fog catchers. Several engineered fogcollection systems are in operation around the world, including one in the highlands of Guatemala that provides a village of 200 people with 7000 litres a day.

Standard fog catchers are large rectangles of plastic mesh suspended on frames. The UW project is exploring new materials and designs that may boost the yield and lower the cost, said Ben Spencer, assistant professor of landscape architecture.

‘‘The more better.’’

Spencer is part of a group of UW faculty that has been working for several years in Lomas de Zapallal, a sprawling squatter community on the northern outskirts of Lima.

Few homes have piped water, so people pay a premium to have it delivered by truck, Spencer said.

Lima is also one of the world’s most arid cities, with some neighbourhoods receiving a scant 12 millimetres of rain a year. But thick fog rolls in off the Pacific between June and December, making the area ideal for fog-catching.

For expert advice, the UW group turned to Robert Schemenauer, founder of FogQuest, a nonprofit based in Kamloops, British Columbia. An atmospheric physicist, Schemenauer pioneered most

water you can get,

the of the fog-collection systems in use today.

The technology will never be a substitute for large municipal water supplies, he said.

It works best in small, mountainous communities where frequent fog combines with a steady breeze needed to propel the mist through collectors.

Any new designs the UW team comes up with will have to be practical, above all, Schemenauer said.

‘‘You need something that’s cheap and strong and will last for 10 years.’’

The UW group is testing fibrous plastic mats used to stabilise slopes and turf.

‘‘We call them our hairy fog collectors,’’ Spencer said.

Early results suggest the greater surface area of the fuzzy mats may extract more water than the standard plastic mesh. Students are also experimenting with collectors of different shapes, including one that resembles the mainsail of a sloop.

The team set up a couple of small test collectors in Lomas de Zapallal, and have been working with the people there to determine whether they’re interested in a system and how they would prefer to use it, Cromwell said.

‘‘The community has to buy into it,’’ he said.

What people seem to want most is water to irrigate parks and green spaces, he said.

In some parts of the world, fog nurtures forests, which absorb the water from the air. But in Lima, those forests were cut down hundreds of years ago, Bolton said.

‘‘This is moisture that kind of doesn’t go anywhere,’’ she said. ‘‘It’s not like we’re diverting a river.’’

Locals hope to use water collected from fog to coax trees to grow again.

‘‘The idea is that you can use fog to put those forests back,’’ Bolton said.

At work: University of Washington faculty member Susan Bolton and student Peter Cromwell measure the amount of water collected in 45 minutes.

Photos: MCT The Seattle Times Water research: The ‘‘hoop house’’ on the campus where low-cost materials are being used to catch fog to create an irrigation system in Peru, where there is plenty of fog but little rain.