How much water can you harvest from fog?

21 12 2009

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How much water can you harvest from fog? I hadn’t really thought about it until, I recently came across the work of FogQuest. FogQuest is a small Canadian all-volunteer organization founded in 2000 that constructs fog collection systems in areas where conventional sources such as wells, rivers and pipelines are not available.

While not as applicable in most of the United States as a primary source of water harvesting (where we use approximately 100gals of water per person per day), the technology is still fascinating and has been effective in developing countries. The system is comprised of a series of screens made of polyethylene or polypropylene erected on poles in areas that frequently experience fog events. According to FogQuest’s website, a 40m2 system can on average collect approximately 200L per day (53 gallons). Like rain harvesting, there are days where no water is harvested, but on some days the system has been reported to collect up to 1000L (264 gallons). FogQuest estimates that a 40m2 system cost between $1,000-$1,500. They have a number of videos on their site that describe the system in more detail (Link to Videos). Andrew R. Parker, a zoologist at the University of Oxford, and Chris R. Lawrence, an investigator at QinetiQ, have developed another fog collection technology based on the Namib Desert Beetle’s wings. They have been able to mimic the beetle’s process for collecting water. It is an interesting application of biomimicry. As the name suggest, the Namib Desert Beetle (see photo) lives in the Namib Desert where only a half-inch of rain falls annually. In response, the beetle has developed a unique survival mechanism. It is able to use its wings to collect water from fog that forms in the early morning and blows across the desert. The researchers discovered that this is accomplished through a series of small bumps on the surface of the beetle’s wings. When the beetle positions its body at 45 degrees the fog collects on its back and runs down the wings to its mouth. Here is a link to a website with more information about the process (link).

Namib Desert Beetle
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In places with high winds, it is thought that this new fog collecting material may be more efficient than the open polyethylene mesh used by FogQuest because the water cannot be blown through it. Other applications being considered for the material include using it to reclaim water vapor from cooling towers to developing tents that would capture fog for drinking water. This material has even been envisioned to reduce or eliminate fog that can disrupt transportation systems (i.e. airports, roads).



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