Vertical farming is the practice of growing crops in vertically and horizontally stacked layers. It often incorporates controlled-environment agriculture, which aims to optimize plant growth, and soilless farming techniques such as hydroponics, aquaponics, and aeroponics. Some common choices of structures to house vertical farming systems include buildings, shipping containers, underground tunnels, and abandoned mine shafts. The modern concept of vertical farming was proposed in 1999 by Dickson Despommier, professor of Public and Environmental Health at Columbia University. Despommier and his students came up with a design of a skyscraper farm that could feed 50,000 people. Although the design has not yet been built, it successfully popularized the idea of vertical farming. Current applications of vertical farming coupled with other state-of-the-art technologies, such as specialized LED lights, have resulted in over 10 times the crop yield as would be received through traditional farming methods. The main advantage of utilizing vertical farming technologies is the increased crop yield that comes with a smaller unit area of land requirement. The increased ability to cultivate a larger variety of crops at once because crops do not share the same plots of land while growing is another sought-after advantage. Additionally, crops are resistant to weather disruptions because of their placement indoors, meaning fewer crops lost to extreme or unexpected weather occurrences. Lastly, because of its limited land usage, vertical farming is less disruptive to the native plants and animals, leading to further conservation of the local flora and fauna. Vertical farming technologies face economic challenges with large start-up costs compared to traditional farms. They cannot grow all types of crops but can be cost-effective for high value products such as salad vegetables. Vertical farms also face large energy demands due to the use of supplementary light like LEDs. The buildings also need excellent control of temperature, humidity and water supplies. Moreover, if non low-carbon electricity is used to meet these energy demands, vertical farms could produce more pollution than traditional farms or greenhouses. An approach to ensure better energy-related environmental performance is to use agrivoltaic-powered vertical farming in an agrotunnel or similar CEA. In this way crops can be grown beneath outdoor agrivoltaics and the solar electricity they provide can be used to power the vertical farming.
Types The term "vertical farming" was coined by Gilbert Ellis Bailey in 1915 in his book Vertical Farming. His use of the term differs from the current meaning—he wrote about farming with a special interest in soil origin, its nutrient content and the view of plant life as "vertical" life forms, specifically relating to their underground root structures. Modern usage of the term "vertical farming" usually refers to growing plants in layers, whether in a multistorey skyscraper, used warehouse, or shipping container.
Mixed-use skyscrapers Mixed-use skyscrapers were proposed and built by architect Ken Yeang. Yeang proposes that instead of hermetically sealed mass-produced agriculture, plant life should be cultivated within open air, mixed-use skyscrapers for climate control and consumption. This version of vertical farming is based upon personal or community use rather than the wholesale production and distribution that aspires to feed an entire city.
Despommier's skyscrapers Ecologist Dickson Despommier argues that vertical farming is legitimate for environmental reasons. He claims that the cultivation of plant life within skyscrapers will require less embodied energy and produce less pollution than some methods of producing plant life on natural landscapes. By shifting to vertical farms, Despommier believes that farmland will return to its natural state (i.e., forests), which would help reverse the effects of climate change. He moreover claims that natural landscapes are too toxic for natural agricultural production. Vertical farming would remove some of the parasitic risks associated with farming. Despommier's concept of the vertical farm emerged in 1999 at Columbia University. It promotes the mass cultivation of plant life for commercial purposes in skyscrapers.
Stackable shipping containers Several companies have developed stacking recycled shipping containers in urban settings. The shipping containers serve as standardized, modular environmental chambers for growing. By stacking the shipping containers, higher density in terms of produce yield/square foot is possible. But, the stacked containers pose the challenge of how to effectively and affordably access the stacked levels. Freight Farms produced the "Greenery" that is a complete system outfitted with vertical hydroponics, LED lighting and climate controls built within a 12 m × 2.4 m shipping container. Podponics built a vertical farm in Atlanta consisting of over 100 stacked "growpods", but reportedly went bankrupt in May 2016. In 2017, TerraFarms offered a system of 40-foot shipping containers, which included computer vision integrated with an artificial neural network to monitor the plants; and were remotely monitored. It was claimed that the TerraFarm system "has achieved cost parity with traditional, outdoor farming" with each unit producing the equivalent of "three to five acres [one to two hectares] of farmland", using 97% less water through water recapture and harvesting the evaporated water through the air conditioning.
In abandoned mine shafts Vertical farming in abandoned mine shafts is termed "deep farming", and is proposed to take advantage of consistent underground temperatures and locations near or in urban areas. It would also be able to use nearby groundwater, thereby reducing the cost of providing water to the farm.
Technology Lighting can be natural or via LEDs. As of 2018 commercial LEDs were about 28% efficient, which keeps the cost of produce high and prevents vertical farms from competing in regions where cheap vegetables are abundant. Energy costs can be reduced because full-spectrum white light is not required. Instead, red and blue or purple light can be generated with less electricity.
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