Greening the Desert Using Seawater, Sun and Ingenuity

Introduction

In the vast sands of Qatar and Jordan, a plan to green the desert using evaporated seawater, indoor agriculture, trees, algae biofuels, solar panels and mirrors is taking root.

The Sahara Forest Project is based around creating value from saltwater, sunshine and flat arid landscapes, three resources that are in abundance throughout many parts of Africa, the Middle East, United States, Mexico and Australia. In other words, the Sahara Forest Project “is designed to utilize what we have enough of to produce what we need more of, using deserts, saltwater and CO2 to produce food, water and energy” (via Sahara Forest Project). Here’s how it works.

The Sahara Forest Project is based around three main components: (1) Seawater-cooled Greenhouses; (2) Concentrated Solar Thermal Power; and (3) Revegetation and Hedges.

Credit: Sahara Forest Project

Credit: Sahara Forest Project

(1) Seawater-cooled Greenhouses

High value crops like tomatoes, cucumbers, peppers and flowers are grown in greenhouses using soilless hydroponic techniques that precisely feed each plant what it needs for water and nutrients. The ability of the greenhouses and hydroponic methods to shield plants from the harsh elements outside and to provide precision feeding make year-round harvests possible, increasing the value of these already lucrative crops.

Greenhouses in the desert need cooling, which would otherwise make them uninhabitable for plants. Cooling is usually energy-intensive and costly.

The Sahara Forest Project utilizes seawater for this purpose, storing the seawater in evaporative pads. Incoming warm, dry desert air is sent over these pads, which cools and humidifies the desert air. Cooler and more humid air relieves stress on the plant to regulate its own temperature, allowing more energy to be devoted to growth.

(2) Concentrated Solar Power

Concentrated solar power (CSP) utilizes mirrors to focus the light of the sun onto a brilliant single point where liquid is stored, creating superheated steam that then drives a turbine and generates electricity.

CSP techniques range from hundreds or even thousands of mirrors focusing onto a single tower, to parabolic dishes and parabolic troughs (shown below).

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Credit: Masdar Energy

Concentrated Solar Power can provide power for up to 6 hours after the sun goes down, allowing for predictable energy production where intermittent sources like solar photovoltaics and wind turbines can’t as easily.

Like greenhouses, CSP plants need a means to cool to achieve the greatest efficiencies in power production. This requires cooling through water or through air, which means importing and using large amounts of water in the former, or exchanging heat with outside air. Using water, called wet cooling, is more efficient and costs less but uses lots of water. Using air, called dry cooling, is more costly and less efficient.

The Sahara Forest Project links its sea-water cooled greenhouses and CSP plants so that “the water-thirsty cooling towers of a typical CSP plant are replaced with a seawater cooling system that utilizes the greenhouse roofs to dissipate the waste heat from the CSP process.”

Credit: Sahara Forest Project

Credit: Sahara Forest Project

(3) Revegetation Hedges

When water the in the greenhouses becomes too salty to be effective moderating the climate within the greenhouses, it is sent outside to irrigate nearby rows of hedges. These hedges serve as a windbreak while also cooling the surrounding micro-climate via increased humidity from their transpiration processes and creating shade.

Revegetating parts of the desert using careful, integrated design allows for crops to be grown outdoors as well as within the indoor greenhouses. Outside of the most sheltered and irrigated sections, the effect of added water in the soil and humidity in the air will tip the scales in favor of natural revegetation occurring as native desert species get a slight advantage in germinating seeds and beginning to green arid lands once more.

Harvesting specific compounds from brine, such as calcium carbonate and gypsum, can be combined with the waste biomass from all of the facility’s activities to rebuild soil fertility. Improving soil fertility adds air pockets, sequesters carbon, holds much more water and increases available nutrients in the soil for plants to access.

In this, and other ways, the Sahara Forest Project aims to develop modern Oases that take what we have in excess-saltwater, deserts, carbon dioxide and sunlight-and use integrated design and specific technologies to create what we need more of-freshwater, clean energy, food, biofuels and green desert lands.

In December of 2012, the first Sahara Forest Project became operational in Qatar, and four months later the first crops of barely and cucumbers. On January 29th, 2014 a promising strain of algae suitable for biofuel production in hot, salty environments was discovered, and is now being studied at Duke University. And on June 22nd, 2014 an agreement was reached to begin a second Sahara Forest Project in Jordan.

Credit: Sahara Forest Project

Credit: Sahara Forest Project

Learn more by about the Sahara Project by checking out this short video: https://www.youtube.com/watch?v=3aZ8E7hj8VU

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