The St Andrews Prize for the Environment

University of St Andrews


2007 Finalist

Seawater Greenhouse Project

Seawater Greenhouse Project

Fresh Water From Thin Air

“The Seawater Greenhouse is a truly new idea which has the potential to impact the lives of millions of people living in coastal, water-starved areas around the world,” says Marco Goldschmied, architect and former President of the Royal Institute of British Architects.

A shortage of water, and the inability to grow crops, is the root cause of much suffering and poverty in the world today. Over one billion people do not have access to a safe supply of water and that number is increasing. As demand outstrips supply, the depletion of ground water is accelerated, causing saline intrusion in coastal regions and thereby reducing further the ability to grow crops.

None of the methods currently used to supply irrigation water in arid regions, including over-abstraction from ground reserves, diverting water from other regions and energy-intensive desalination, are sustainable in the long term.

The Seawater Greenhouse, designed to provide a cost-efficient and sustainable solution, distils fresh water from seawater and cools the growing environment. This creates optimum conditions for cultivation, enabling crops to be grown where otherwise it would be difficult, or impossible. Cooler and more humid conditions enable crops to grow with very little water. Crop yield and quality is also increased because crops are not stressed by excessive transpiration. In Oman, one of the hottest countries on earth, the daily outdoor irrigation rate in winter is four litres per square metre, increasing to 11 litres per square metre, in summer. Inside the Seawater Greenhouse, these rates are substantially reduced to a range of 1 - 1.4 litres per square metre. This represents a four to eight-fold saving and shows that part of the solution to the world’s water shortage may be to create conditions that use less water and at the same time grow better crops.

The Seawater Greenhouse uses very little electrical power compared with conventional air conditioning and desalination processes, because the energy for cooling and distillation is provided by the sun and wind directly. As the modest demand for electrical power for fans and pumps is proportional to sunlight, we propose in future to meet this need with photovoltaic panels, without the need for batteries and inverters.  In addition to carbon dioxide savings, this will enable off-grid, and remote communities, to produce crops and fresh water.

Conventional greenhouse operations frequently have environmentally damaging consequences, primarily through over-abstraction of water and over-use of pesticides. In Almeria, the most arid region of southern Spain, damage is particularly severe. This region alone has 20,000 hectares of greenhouses, which accounts for 10 per cent of greenhouse coverage in the Mediterranean basin as a whole.

However, our seawater evaporators, through which all ventilation air must pass, are very effective at removing airborne contaminants, including salt spray, dust, pollen and insects. This ‘air scrubbing effect’ is such that in all our pilot greenhouses to date, we have never had to use pesticides.

We now plan to develop specific solutions for the Mediterranean region, where both the use of groundwater and pesticide will be reduced or eliminated.

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