Mining water from gypsum

Water resources in the world are scarce and unevenly distributed. In deserts, the only source of drinking water is groundwater, often saline and of poor quality. In many places, the groundwater levels have dropped dangerously due to overexploitation. Gypsum deposits, that are very common in deserts, are a potential source of drinking water, a fact that is realised by very few people. Gypsum contains 20% of water by weight, and in many arid and desert countries, there are billions of cubic meters of gypsum, representing trillions of litres of clean drinking water. It takes only moderate heating, to temperature around 100°C, to liberate this water and convert the gypsum into bassanite or anhydrite. Such temperatures can be reached by solar power, or alternatively, the heat from flaring oil wells can be used. Anhydrite has a considerably smaller volume than gypsum, so the conversion of shallow underground layers of gypsum into anhydrite creates a subsidence, which can serve as a reservoir for the liberated water. Holland Innovation Team (HIT) is working on this project since 1987, and we have indicated that the macro-engineering concept of dewatering gypsum deposits can solve the water problem in many dry areas in future, for drinking purpose as well as for drip irrigation. We would like to thank Saint-Gobain Gypsum (Cormeilles gypsum mine in Paris) and the SAMIA mine (Nouakchott, Mauritania) for the donation of pure gypsum blocks for testing purposes. We aim for a pilot test at a suitable desert location, in which several modes of heat supply and water capture will be tested. Several possible drilling and capture configurations are described in this paper.