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David Bradley ISSUE #74
July 2008
Rocky Water Source

Getting water from rock could be a whole lot easier than getting blood from a stone. Gypsum, a rocky mineral abundant in desert regions where fresh water is usually in short supply, could become a novel source of fresh water there, as well as providing a way to make use of "flared" gas from oil fields.

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Peter van der Gaag of the Holland Innovation Team, in Rotterdam, The Netherlands, explains that, chemically speaking, gypsum is calcium sulfate dihydrate, and has the chemical formula CaSO4.2H2O. In other words, for every unit of calcium sulfate in the rock there are two water molecules, which means gypsum is 20% water by weight. van der Gaag suggests that a macro-engineering project could be designed to tap off this water from deposits of desert gypsum, which could release trillions of liters of clean drinking water for such regions.

The dehydration process requires energy, but this is not in short supply in deserts, where sunlight is abundant, and in many cases, wasted by oil and gas fields flaring unwanted gas. van der Gaag explains that it takes only moderate heating to liberate water from gypsum. "Such temperatures can be reached by small-scale solar power, or alternatively, the heat from flaring oil wells could be used," he says. He adds that, "Dehydration under certain circumstances starts at 60 Celsius, goes faster at 85 Celsius, and faster still at 100 degrees."

The dehydration of gypsum results in the volume of the material being reduced substantially, so that the release of water will cause local subsidence, forming an instant reservoir for the water. "The macro-engineering concept of dewatering gypsum deposits could solve the water shortage problem in many dry areas in the future, for drinking purposes as well as for drip irrigation," concludes van der Gaag. Small-scale tests have already proved successful.

Int J Global Environ Issues, 8: 274–281, 2008