With the world population rising, farming is becoming very inventive. Crops are also being pushed further into areas not usually thought of as fertile farmlands.
By Nicole Buckler
Deserts are often used as symbols of infertility and lost hope. Most of the world’s deserts formerly supported vegetation of some sort, from lush rainforests to spindly woods. Now with the deserts creeping eerily across the planet, humans have decided to do something to stop the sandy march.
So how do we get these deserts back to a fertile state? Humans might just have the answer. We bring water to them. And this is not just any water, this is seawater. That’s right, seawater could be the answer to reviving the world’s deserts. And before you raise your eyebrows at the idea of salty water regenerating a desert, some fascinating experimental projects currently being undertaken are already showing signs of being utterly feasible, even profitable.
A bunch of mega-innovative boffins have set out to regenerate the most famous desert of all. Called The Sahara Forest Project, this outfit came together to put water in the right place and get the salt out. Their plan was to change seawater into fresh water by combining different existing green technologies and cultivate areas of desert that are otherwise barren, desolate places of poverty. The system they have invented mimics nature as closely as possible and in doing so creates a little biosphere of green hope. The experiment so far as gone as planned and it promises to rearrange the way we think about deserts.
The saltwater greenhouse technique involves pumping seawater (or allowing it to gravitate if below sea level) to an arid location. After it has arrived at its destination, it goes through two different processes. First, it is used to humidify and cool the air inside a greenhouse, and second, it is evaporated by solar heating and distilled to produce fresh water. Finally, the humidified air is expelled from the greenhouse and used to improve growing conditions for nearby outdoor plants.
While desalination has always been expensive, by using new solar technologies (concentrated solar power or CSP) this has become vastly more economical. CSP systems use mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. In a desert, the sun is so intense that without question it produces so much power that it is almost a license to print money. In fact, the energy is so abundant that there is enough to desalinate a truckload of seawater and run the greenhouse and there is still enough leftover energy can then be used to power the local community. So far we have cheap desalination, and leftover electricity. It’s all good.
Currently, existing greenhouse facilities can use up to five times more water to irrigate crops than the region’s average annual rainfall. However the new system using seawater works by mimicking the natural hydrological cycle. No rainwater or freshwater is needed. Surplus freshwater produced can be used to water surrounding orchards and a crop called Jatrophra, which can be turned into bio-fuel for transportation and other needs.
To be successful long-term the project does have to be a profitable business. No problem! There are many opportunities for multiple income streams. Before the seawater is evaporated, it can be used to grow microalgae, seaweed, shellfish, shrimps and fish. The waste products of these processes can be used as a fertiliser and soil conditioner for external vegetation. This then reverses the trend over the past century of a steady loss of minerals from the land. But the minerals harvested from the sea also have other uses – calcium carbonate which is deposited on the evaporators can be used in the construction industry. Sodium chloride has many industrial applications. Magnesium chloride is a valuable desiccant for low energy cooling systems and lithium is increasingly demanded for high performance electrical batteries.
As you can see here in Oman, an experimental facility slowly makes the surrounding area more fertile as the waste water is used to irrigate the surrounding land.
Picture 1: The surrounding area of the Seawater
Greenhouse at the time of construction.
Picture 2: Two years into operation. Although the
picture is taken from another angle, the effect
of revegetation is clearly visible.
Picture 3. Growing cucumbers inside the
Seawater Greenhouse in Oman
The quality of the soil can be further enhanced by the use of washed seaweed – rapidly growing and mineral-rich algae. There is a tremendous interest in the possibilities for growing microalgae for energy purposes. The result is restorative growth: reforestation and creation of green jobs through profitable production of food, freshwater, biofuels and electricity. So far three projects have been built and while still experimental, have been wildly successful in Tenerife, Abu Dhabi, and Oman.
Watch this space, soon the deserts may be perfectly viable places to farm.