Sea water constitutes by far the biggest fraction (93%) of the water on earth. Though there are important local variations, it usually has a salt content of about 35,000 mg/l, or 3.5%, making it useless for consumption by either man or beast, and marginal for agricultural irrigation purposes. There has been a certain amount of research, and some success, into the possibilities of using seawater for irrigation, but suitable crops are few, the process is costly, and the yields are low.

As most people know, there has also been a huge amount of Research and Development done with respect to removing the salt from seawater. This has gone far enough, and so many large desalination plants are in satisfactory operation worldwide that this may now be described as a mature industry. Global R&D is now organized and coordinated from the Middle East Desalination Research Centre in Oman.

Unit costs, even for the biggest and most efficient plants, approach or exceed $1.00 per m3, so that the water produced can be used for only the highest- valued uses. The most important parameter in the cost equation is energy; when costs under $1.00/m3 are reported it is usually because of an unusually low-priced energy source. Desalination will not soon be the answer to the world water problem.