the plants resulting in a less run-off of nutrient
rich water and thus reducing the risk of environmental pollution significantly compared to traditional agricultural practises.
The basic hydroponic systems have been modified
to include aeroponics where instead of the roots
being immersed in a nutrient solution, the roots
are misted at regular frequencies with a nutrient
solution containing all the nutrients plants need.
This not only reduces the amount of water needed
considerably (up to 80%) but also maintains a well
aerated growth environment for the roots, essential for its optimal functioning. The water use efficiency of these city farms can further be improved
by addition of a rainwater collection system and
even using grey water from the surrounds. Growing crops indoors also allow for control of the environmental conditions which if done correctly
allow for maximum yield per square meter, all
year round. In this regard the advent of LED lighting is also resulting in a revolution in protected
cultivation since these lights make it possible to
supply light energy to crops in the exact spectrum
that they require. Standard grow lights in greenhouses such as the high pressure sodium and metal halide lamps are often energy inefficient in the
sense that a large portion of the light emitted is
not used by the plants and a lot of heat is also
generated which needs to be extracted again using expensive air conditioning systems.
During the last 8 years several commercial vertical
farms have been established in large cities in AbuDhabi, the Netherlands, Japan, South Korea, SinFigure 4: An automated growing
system for hydroponically grown
lettuce.
Figure 3: The Verti-Gro hydroponic
system used to produce lettuce
and other leafy greens.
gapore, Canada and the United
States proving that this is not just
an unrealizable dream. One of the
largest, Nuvege located in Japan,
produces 6 million heads of lettuce
a year in, for customers including
Subway and Disneyland Tokyo.
They do this in only using supplemental lighting which they augment according to the carbon dioxide levels to optimise photosynthe-