Growing indoors can also protect crops from the effects of climate
change, such as increased global temperatures and drought, which can
reduce crop yields in some areas. When crops are grown indoors, the
controlled internal environment protects plants from these effects.
If vertical farming is so great, why isn’t everyone adopting it? Vertical farming has its challenges. Open-field agriculture relies entirely
on energy from the sun, so, when it is available, this source of energy
is free. Crops grown indoors receive their energy from artificial light
sources, which rely on electricity.
Another issue is that the artificial light sources, called grow lamps, emit
heat, which can damage plants if they are placed too close to the plants.
So the plants need to be spread out, and the indoor space needs to be
cooled to compensate for the added heat from the lamps.
To address this particular challenge, vertical farmers are increasingly
using another type of lamp, called a light-emitting diode (LED), which
is a light source that is compact, energy-efficient, and can be designed
to emit a particular wavelength (unlike a grow lamp, which emits light
from the entire visible spectrum).
Plants do not use the entire spectrum of light. Research has
shown that plants mainly absorb only portions of the light spectrum.
Chlorophyll—a pigment that gives plants their green color—absorbs
peak wavelengths around 450 nanometers and 650 nanometers (blue
and red color, respectively) (Fig. 1). LEDs can be designed to emit only
these wavelengths, so giving plants only the light they need—red and
blue light—saves energy.
LEDs are also less costly than grow lamps and produce little to no
heat and can be placed next to a leaf, which allows crops to be closely
stacked on top of each other.
Another challenge of underground farming is cost, which can be
high—city land is expensive and LED lights are expensive, too. Current
estimates for the price of food grown underground are on the order of
$5 per kilogram ($2.50 per pound), which is reasonable for fruits and
vegetables but is not practical for bulk crops, such as grains, corn, and
Controlling plants with light
Light can also influence how a plant grows. According to Kevin Folta,
a scientist who studies the effects of light color on plant growth at the
University of Florida, Gainesville, the light spectrum emitted by
LEDs can be tuned by varying the amount of red, infrared,
and blue light in order to optimize the growing conditions of
Also, a specific combination of light colors tells a plant how to grow in
a specific way. For example, a large amount of red light causes a plant to
flower, and a predominantly blue light causes a plant to grow.
Plants convert the energy from light—whether from the sun or from
LEDs—into chemical energy, a process called photosynthesis. This
process uses water and carbon dioxide from the air to produce carbohydrate molecules, such as sugars, which are used by the plants to grow.
Photosynthesis can be summarized by the following chemical reaction:
6 CO2 + 6 H2O ➞ C6H12O6 + 6 O2
Growing plants underground with LEDs can be applied in many parts
of the world, including urban areas, which reduces the demand for arable land. This explains why the abandoned World War II shelters under
the city of London are being used to grow crops and
why similar projects are being built in South Korea,
Singapore, and Sweden.
Agriculture has a huge influence in our lives
because everyone needs to eat. As the global population grows, so does our need to produce enough
food to meet everyone’s needs. But more land will
be required to grow the crops needed to feed more
people, which places an increasing demand on the
limited arable land available on Earth. One way to
solve this problem is to produce food sustainably,
and vertical farming might be part of the solution.
Hickey, S. The Innovators: London Air-Raid Shelters Sprout
a Growing Concern. The Guardian, Sept 13, 2015:
the-innovators-london-air-raid-shelters-sprout-a-growing-concern [accessed July 2016].
Spence, C. Plant Whisperer. University of Florida, Office of
Research. Explore, Dec 14, 2014: http://explore.research.
ufl.edu/plant-whisperer.html [accessed July 2016].
David Latchman is a science writer who lives in
Bakersfield, Calif. This is his first article in ChemMatters.
Figure 1. (A) A traditional grow light, which is used to grow crops underground, emits light from
the entire visible spectrum, even though many crops absorb only portions of the visible spectrum.
A green plant—such as the one shown here—typically absorbs wavelengths that are only in the
blue and red regions of the visible spectrum. Also, grow lights emit a lot of heat. (B) A light-emitting diode (LED) lamp saves energy because it generates only the wavelengths of light the
crops actually absorb, and it emits less heat than grow lamps.
Vegetables that are
do not need soil and
sunlight. Instead, the
here grow in solutions
that contain water and
nutrients and rely on
artificial lamps for