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Hydroponics: a little water goes a long way, The National 08.08.2008

From the Hanging Gardens of Babylon, to Nasa research into growing plants on Mars, hydroponic farming has offered a resource-efficient and adaptable method of agriculture. The method uses less water and space than traditional farming, does not depend on soil quality and produces higher yields. So why have we not heard more about it? Hydroponic agriculture involves growing plants in water enriched with nutrients, or in an inert medium like gravel or rock wool, through which nutrient-enriched water passes. The growth of cress on a soggy piece of paper towel is the most basic example. There are currently commercial hydroponic farms in America’s Sonoran Desert, Canada, Western Europe and Japan, producing vegetables with great commercial success. A 220-acre hydroponic farm, Thanet Earth, is being built in Kent in England and should be operational, growing tomatoes, cucumbers and peppers, by 2010.

Figures recently revealed that the UAE has the highest per capita consumption of water in the world, with irrigation accounting for 50 per cent of the water used. Commercial hydroponic agriculture requires 5 per cent of the water, and 13 per cent of the space, that field based agriculture needs to produce the same yield. And in greenhouse conditions, plants can be grown year round and much closer together. Furthermore, farmers estimate that 90 per cent of the water used in hydroponic farming can be recycled. Given the UAE’s largely arid landscape, hydroponics are particularly attractive for the UAE.

City Farm, halfway between Abu Dhabi and Dubai, uses hydroponic technology brought to the UAE by its Australian manager, Rudi Azzato. In the middle of the farm is a huge 1,000-square-metre state-of-the-art greenhouse, or ‘Little Holland’ as it is affectionately known. The climate inside the greenhouse is computer-controlled to 18 degrees Celsius at night and mid-20s during the day, with permanent humidity at 65 per cent.

The farm produces lettuce, herbs, tomatoes, cucumbers, peppers and strawberries that grow in a rock wool made from basalt rock which is heated up to a high temperature and then spun to give it a wool-like consistency. “The rock wool is recyclable, retains water well and allows oxygen through to the roots,” Mr Azzato says. If you buy a head of lettuce from the farm, the rock wool will still be attached to the roots, enabling the lettuce to last longer in transit and in your fridge.

Rock wool cubes are placed in PVC troughs on a rotating growing system (RGS) that rotates the troughs 6.5 metres like a Ferris wheel. A shallow stream of nutrients is then passed through the troughs where they are absorbed by the bare roots of the plants. This method of hydroponics is called the Nutrient Film Technique and was developed in the UK in the 1960s. One of the advantages of the RGS system is that there is greater yield per square metre, rather like vertical farming. As Mr Azzato points out, “to produce the same yield in traditional field farming you would need eight times this floor area”.

Pesticide use is kept to a minimum at City Farm. Where possible, Mr Azzato uses organic pesticides and alternative methods of pest control. In one of the greenhouses he explains: “Here, we use ‘companion planting’, planting coriander and other herbs next to basil. The perfume of the basil dissuades aphids and white fly from settling and enhances the flavour of the other plants.” Soil-borne diseases, which can wipe out a crop, are avoided, since no soil is used in this process.

Controlled environment agriculture using hydroponics, has been tried and tested before in the UAE. In 1970, Sheikh Zayed invited a team from the University of Arizona to set up a commercial hydroponics farm on Saadiyat Island. Sheikh Zayed was impressed by the results of the university’s team in Mexico, where, according to a team member, Dr Miguel R Fontes, the aim had been “to find economical means of making a coastal desert agriculturally productive”.

The team built greenhouses and raised plants hydroponically by feeding their roots with commercial-grade fertiliser in distilled seawater. The greenhouses were evaporatively cooled using seawater and fans. They grew lettuce, aubergine, tomatoes and peppers to great success. “Yields for the Saadiyat greenhouses generally are much higher than field cultureĀ…[and] higher too than many conventional greenhouse operations”, reported Dr Fontes. Three years into the project, the UAE was exporting vegetables to Lebanon.

According to the Project Director, Dr Merle Jensen, Professor Emeritus at the Department of Plant Sciences at the University of Arizona, shortly after the University of Arizona team left, the project was moved to Al Ain so that the Saadiyat Island development could start. What happened to the greenhouses after that is not clear. There are, however, significant hurdles to overcome in this method of modern farming – the high initial capital cost of greenhouses like ‘Little Holland’ in particular. “Building this cost us millions of dirhams,” said Mr Azzato, “the greenhouse is fully computerised, every aspect of the environment around the plants is controlled”. Mr Azzato has since built one further greenhouse, in which he grows herbs. This one is lower technology, and cheaper to build and run as it is temperature-controlled by fans and uses evaporative cooling (much like the Saadiyat greenhouses in the 1970s). However, this will not be productive in the summer, when heat and humidity increase.

Another issue in achieving an acceptable return on the initial investment is the price of the produce. As Mr Azzato explains, “we have European seeds, grown using European technology and in a European climate, arriving at the supermarket fresher than imported lettuce, but when the supermarkets hear that these were grown in the UAE, they only offer us local prices”. The UAE currently has a huge carbon footprint. To be commercially viable the greenhouses need to function year round, meaning some form of air-conditioning throughout the summer. Whether such use of energy outweighs the benefits of decreased water use and higher crop yields is an issue consumers and the Government need to weigh.

However, technological advances in growing techniques and the materials used to build greenhouses are improving the energy efficiency of greenhouses all the time. Products such as a new near-infrared filtering plastic, which limits solar heating of greenhouses without seriously impairing light availability, are an energy efficient way of keeping air temperatures low. In a colder climate like the UK, new technology, in the form of a combined heat and power installation (CHP) attached to a greenhouse complex, can be used to generate electricity for a farm to use and to sell.

So, how viable is large-scale hydroponic agriculture in an environment such as the UAE? Very, according to Professor Louis Albright of Cornell University in New York. “To my mind, greenhouses in very hot climates are still viable as long as design, operation, control and crop selection are optimised.” A method of hydroponics called “floating hydroponics”, developed by Dr Merle Jensen at the University of Arizona in the 1970s, is used extensively at Cornell. Using this process, lettuce can be produced in temperatures of 30 degrees Celsius and even higher. As Prof Albright explains, “this requires very little energy – the pond of water can be well insulated and the plants float in styrofoam panels that add insulation at the top surface, making, in effect, a closed and insulated box for the solution.” He also recommends the evaporative cooling technique used at City Farm in its herb greenhouses, suggesting this be used for other produce such as tomatoes, peppers and cucumbers. “In fact cucumbers love hot temperatures”.

While there are some Government grants of up to Dh 5,000 toward the cost of a conventional greenhouse, these subsidies are not enough to construct a hydroponic greenhouse. If consumers and the Government can set these advantages off against the diminishing energy cost of cooling greenhouses, and the Government is willing to provide financing to start up businesses, the UAE could again be a pioneer in agriculture.

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