There is new technology in the market, called ‘Seawater Greenhouse’.
A seawater greenhouse is a greenhouse structure that enables the growth of crops in arid regions, using seawater and solar energy. The technique involves pumping seawater to an arid location and then subjecting it to two processes: first, it is used to humidify and cool the air, and second it is evaporated by solar heating and distilled to produce fresh water.
Namibia lies in the second driest area in Africa after the Sahara and is the most arid country in Sub-Saharan Africa. Travellers often refer to Namibia as an “arid Eden”.
This vast desert and semi-arid landscape attracts many tourists every year, yet poses hardship for the population. Scarcity of freshwater is a constant threat to the daily lives and survival of farmers and industries, in both rural and urban areas.
Rainfall decreases from the northeastern parts of the country towards the south and west, ranging from 700 mm to less than 50 mm annual rainfall. Water scarcity involves water stress, water shortages or deficits and water crises.
The relatively new concept of water stress refers to difficulty in obtaining sources of freshwater for use during a period of time. It may result in further depletion and deterioration of available water resources. While the changing climate seems to foster extreme weather situations, such as droughts – and in some cases, floods – the stress on water resources is constantly increasing due to industrialisation and changing living conditions.
The above-said technology was introduced by British inventor Charlie Paton in the early 1990s and is being developed by his UK company, Seawater Greenhouse Ltd.
The more concentrated salt water may either be further evaporated for the production of salt and other elements, or discharged back into the sea. The seawater greenhouses are a timely response to the global water crisis and peak water.
Namibia could benefit from this technology (seawater greenhouse), as the country has experienced water scarcity, which has negative impacts on the environment, including lakes, rivers, wetlands, and other freshwater resources.
A seawater greenhouse produces crops year-round in hot dry areas using only seawater and sunlight. Tomatoes, cucumbers, peppers, lettuce, strawberries, herbs – anything that can be grown in traditional greenhouse (including omahangu and maize) – can be grown in seawater greenhouses, but the main component of desert greening is the planting of trees.
Trees store water, raise water from underlying aquifers, reduce evaporation after a rain, attract animals (and thereby fertility through faeces), and they can cause more rain to fall (by temperature reduction and other effects), if the planted area is large enough.
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.
According to the World Health Organisation, about 20 percent of the world’s people live in regions that do not have enough water for their needs. With the global population increasing by 80 million each year, a third of the planet will likely face water shortages by 2025.
This looming water crisis is inextricably linked to food production, because agriculture accounts for 70 percent of all fresh water used, and obtaining irrigation water in arid regions has serious environmental impacts. Drilling wells can deplete groundwater, and desalination is energy intensive and leaves behind concentrated brine.
The seawater greenhouse, however, provides what may be an economical and sustainable way of producing fresh water and crops in hot, dry regions near the ocean.
President of the Royal Institute of British Architects Marco Goldschmied said in 2000: “The seawater greenhouse is a truly original idea which has the potential to impact on the lives of millions of people living in water-starved areas around the world.”
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 utilise what we have enough of to produce what we need more have, using deserts, saltwater and CO2 to produce food, water and energy.
Namibia is known to have a high velocity winds in the desert that blow soil, depositing some on neighbouring fertile lands, and causing shifting sand dunes within the desert, which bury fences and block roads and railway tracks.
A permanent solution to this problem of shifting sand dunes can be provided by planting appropriate species on the dunes to prevent further shifting and planting windbreaks and shelterbelts.
These solutions also provide protection from hot or cold and desiccating winds and the invasion of sand.
Finally, in suggestion, all the stakeholders (public and private sector) should put in effort (in terms of financial resources, technology transfer, capacity building) in line with the national development programme, Vision 2030 and Harambee Prosperity Plan to make Namibia’s desert evergreen using seawater.