RNW, 2 May 2011, by Johan Huizinga
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| (Photo: RNW) |
Dutch hothouses used to have a reputation for wasting energy. But nowadays it’s the most innovative sector in the Netherlands, producing food extremely efficiently using sustainable energy. Even the Chinese are interested.
China, like the Netherlands, does not have enough agricultural land to feed its own population. Dutch intensive greenhouse systems could help increase food production in China.
Professor of greenhouse farming at the Agricultural University of Wageningen Olaf van Kooten explains:
“Cultivation under glass is extremely efficient in its use of water and energy. In the future, we will have to feed around 15 billion people across the world, and this could be a key to the solution.”
Water
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Excess warm water is stored underground (Photo: RNW) |
Stef Huisman grows tropical plants and trees for offices. He uses a closed water system. His nursery has trees standing in two to three centimetres of water. Every week, the water is filtered for sand and ultra violet rays and reused.
“That is all the water we need. The rain that falls on the roof is enough to water the plants. We don’t use any ground water.”
Professor Van Kooten thinks this technique could be an important export product.
“If we continue like this, the only water we use will literally be the water in the product. To produce a kilo of tomatoes, you will only need a litre of water.”
Ground heat
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Water is pumped from a depth of three kilometers (Photo: RNW) |
The use of the ground heat to heat the greenhouses is just as important. Ted Duijvestijn has drilled a 3-kilometre-deep shaft to heat his tomato greenhouses in Pijnacker. The system pumps salt water which is 75 degrees Celsius upwards to the greenhouses. Once the water cools it is pumped back into the ground, where it reheats again.
The system, which was installed in March, is already making 60 percent savings. Once the electric pumps are powered by his own windmills, the greenhouses will more or less only run on sustainable energy. There will even be excess energy and warm water produced so that greenhouse owners will also become energy suppliers.
LED lighting
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Rob Baan uses four colours in LED-lighting (Photo: RNW) |
And then there are the lights which are used to help plants grow. Vegetable grower Rob Baan has replaced his with low-energy LED lights which give exactly the right colour. Next to the greenhouse is a windmill to provide the energy for the LED lights.
In the summer the greenhouses are heated by the sun, producing temperatures above 50 degrees. Excess warmth is used to heat water, which is stored underground for the winter.
No pesticides
Wouldn’t it be easier to cultivate food in regions where no greenhouses are needed. Mr Baan very firmly says “No.”
“There are no insects here. Our greenhouses are either free of insects or we have predators in the greenhouses which eat them. We do not spay pesticides on the plants. Our production methods are becoming more and more sustainable. In the future, these kind of farms will be built close to cities, so that food can be produced locally.”
Meanwhile he has started up his own businesses in the United States and Japan.
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