A project to “green” desert areas with an innovative mix of technologies—producing food, biofuel, clean water, energy, and salt—reached a milestone this week in the Gulf state of Qatar. A pilot plant built by the Sahara Forest Project (SFP) produced 75 kilograms of vegetables per square meter in three crops annually, comparable to commercial farms in Europe, while consuming only sunlight and seawater. The heart of the SFP concept is a specially designed greenhouse. At one end, salt water is trickled over a gridlike curtain so that the prevailing wind blows the resulting cool, moist air over the plants inside. This cooling effect allowed the Qatar facility to grow three crops per year, even in the scorching summer. At the other end of the greenhouse is a network of pipes with cold seawater running through them. Some of the moisture in the air condenses on the pipes and is collected, providing a source of fresh water.The plant gets all its energy from solar power and when any is left over it is used for desalination, creating yet more fresh water. Obviously these pilot projects are not economically viable, and even when they are scaled up they will probably be an expensive way to grow food. But in the Middle East people worry that wars will erupt over the control of fresh water needed for irrigation, and technologies that provide food from salt water and sunlight may be essential to keeping people fed and the region peaceful.
In the long run this points to the problem with all doomful prophecies about the human future: we are very clever. If we are steadily exhausting the world's supply of fresh water, we are also developing the technologies that will allow us to make more as needed.