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Salt of the earth

As the ocean covers three quarters of the surface of the earth, little wonder people see it as a possible source of freshwater. That basically means desalinating it to make it at least clean enough for agriculture and even good enough to drink. How does it work? Distillation is the cheap option, responsible for most desalinised water, but a newer filtering process using membranes, called reverse osmosis, now accounts for nearly half the world’s capacity to turn ocean into freshwater.

Desalination is not a new process. Since Kuwait’s first large-scale desalination plant in the 1960s, it has spread into use in over a hundred countries, with Saudi Arabia accounting for about 24% of total world capacity. The world’s largest desalination plant in Ashkelon, Israel, uses reverse osmosis to produce 100 million m3 of water per year. The industry is mature, so few if any subsidies will be needed to develop it further, experts say. Also, the cost of desalinisation has declined to less than US$2 per thousand gallons (less than US$0.50 per m3), making it competitive with, say, shipping surface water over long distances. AB

©OECD Observer No 254, March 2006