Above: Image © istockphoto.com/momokey
As urban populations increase, the demand for food grows. Meanwhile, organic and locally-grown food has become more popular and there is a growing awareness of the pollution associated with transporting food over great distances. Vertical farming is one response to these trends. In vertical farms, food is grown indoors in multi-story buildings in the same cities where it will be eaten. The world “vertical” refers to both the use of tall buildings, such as skyscrapers, and the growing of crops in racks stacked on top of each other.
Did you know? Chlorophyll is the particle in plants that make them appear green. It absorbs energy from light and uses it to convert carbon dioxide into carbohydrates (sugars) and oxygen for plants to use for growth.Vertical farms are starting to appear in the centers of the world’s largest cities, where more and more of the world’s food is being consumed. These operations not only make more fresh food readily available, but having farms located in city centres also reduces pollution since food does not need to be transported as far. The use of tall buildings means that less land is required and more crops can be grown on the same footprint (the same-sized area of land), compared to a traditional farm. Since they are grown indoors, crops in vertical farms are not exposed to the elements, allowing for year-round cultivation and providing protection from extreme weather conditions.
Vertical farms are like greenhouses, except all crops are grown hydroponically, with controls for such factors as light, temperature, and water. Hydroponics involves using a water-based system instead of soil. Plants grow in an inert substance (one that does not react with anything) combined with a solution of nutrients and water. The acidity (pH) of the solution is adjusted so that roots will easily take up nutrients, allowing plants to grow faster than in soil. The environment is carefully controlled, distributing just the right amount of nutrients, recycling water, and removing moisture from the air to avoid mould. There is no need for pesticides so long as farmers are careful to keep out pests and ensure proper cleanliness, a task made easier by the highly-controlled environment.
Did you know? Vertical farms made by Green Spirit Farms are designed to work well in areas that are dry. They recycle the water and end up using 98 percent less water per crop than traditional farming.One concern about vertical farming is the use and cost of energy for lighting. Light can be provided by either natural sunlight or light emitting diodes (LEDs). In Singapore, which is near the equator, a vertical farm built by a company called Sky Greens relies on sunlight to grow its crops. The farm is four storeys high and uses racks that are rotated on an elevator to access sunlight, simulating a natural light-dark cycle. This type of system works best in climates with a lot of natural sunlight.
However, only cities located near the equator usually receive enough year-round sunlight that they can depend exclusively on natural light. So most vertical farms have to use LEDs as an artificial light source. Nuvege, a company located in Kyoto, Japan, does not use any natural light. Instead, red and blue LEDs are used. These colours correspond to the two different wavelengths of light absorbed by the chlorophyll in the plants.
Although LEDs are more efficient that other types of lights, they are still only about 28 percent efficient, meaning that most of the energy they consume is not converted into light. However, LEDs used in vertical farms do not need to be constantly on. As in nature, plants grown indoors require changes in light as well as dark recovery periods, during which photosynthesis is turned off and energy is used for growth. Using appropriate timing and different LEDs to reflect these changes can increase yield. Supervision of vertical farms is minimal, with automated controls that can sometimes even be managed with a smartphone app.
Besides large cities, vertical farms could also be developed on the outskirts, where the cost of land is lower but distances to market are still lower than in rural areas. Vertical farms can also be used in combination with rooftop gardens to increase crop yield. And with advances in technology, you could be seeing produce growing in your city in the near future.
Green plants & Chlorophyll (Causes of Color) Growing crops in buildings proposed as solution to world's food woes (Grant Buckler, CBC News) Vertical Farm Project - Agriculture for the 21st Century and Beyond (Dickson Despommier) Vertical farming: Does it really stack up? (The Economist) Vertical farms sprouting all over the world (Paul Marks, New Scientist) What is hydroponics? (Simply Hydroponics and Organics)