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In this type of system, horizontal grow beds are stacked vertically in tiers. This arrangement means that in a greenhouse, only the upper bed will be facing direct natural light, and supplementary lighting needs to be provided for the lower beds, usually from lights attached to the base of the bed above. While in principle this means that the grow beds could be stacked as high as the greenhouse or production unit allows, in practice growing at height means that the system is more difficult to manage, requiring the use of scissor lifts for planting, maintenance and harvesting, and additional energy to pump the water to all levels. The shorter the stature of the crop, the more tiers can be inserted into the system, which means that most stacked horizontal beds are used for growing microgreens. The grow beds may be DWC, NFT or media beds. For example, in the UK Hydrogarden produces various models of the V-Farm: the four and five tier NFT system suitable for herbs, leafy greens and strawberries can grow up to 35 plants/m2, while the five tier flood and drain system can grow 4.6 m2 of microgreens on a footprint of 1m2.
Canadian company VertiCrop has developed a high density, fully automated, closed-loop conveyer NFT hydroponic vertical farming system (Figure 9). The system has been installed at the Local Garden rooftop greenhouse in Vancouver to grow microgreens, leafy greens and herbs. 3000 plant trays stacked 12 high move on an overhead conveyor system, thereby ensuring maximum sunlight for each plant.
Figure 9: The VertiCrop system https://grow.verticrop.com/vertical-farming/
The Verticalis system (Figure 10), developed by Friendly Aquaponics in the USA, is designed to be deployed in rows inside a greenhouse, with the units of NFT channels stacked right up against each other, long side to long side, in order to maximise the use of space; in such a configuration, which requires the use of artificial light, it can produce 300 plants/m2. Castors on the base of the units mean that they can be moved easily, and each rack of channels can be slid out from the unit to facilitate planting, maintenance and harvesting operations.
Figure 10: The Verticalis system https://www.friendlyaquaponics.com/product/vertical-aquaponics-growing/
There have been few attempts to integrate aquaponics with commercial vertical farms. At 8361 m2, FarmedHere in Chicago (Figure 11) was hyped as the first of its kind and the largest indoor vertical farm in America. It was opened in 2013 and was expected to become a new model for growing produce efficiently in a high tech manner. However, it closed down in 2017 due to high energy and labour costs. The farm resided in a two-storey, windowless warehouse. By stacking the fish tanks and DWC grow beds vertically, the facility contained 13,935 m2 of growing space (1.4 hectares), and produced 136,000 kg of leafy greens and herbs per year (Al-Kodmany 2018).
Figure 11: Farmed Here, Chicago https://www.wsj.com/articles/vertical-farming-takes-root-1449237679
Greens and Gills opened in the basement of The Plant, Chicago (see also Chapter 13) in 2012. The 300 m2 farm used a 6-tier DWC aquaponic system to grow leafy greens, herbs and microgreens. The tilapia and greens were sold to restaurants, grocery stores and local distributors. The company closed in 2015 and the facility was put on the market with an asking price of $255,000 (Sijmonsma 2015). However, it remained unsold, and the aquaponic system is currently used by Plant Chicago to run monthly training courses.
In the UK, GrowUp Urban Farms combine aquaponics with vertical growing technologies and Controlled Environment Production (CEP) to produce year-round harvests of salads and herbs. From 2015 GrowUp operated ‘Unit 84’, a commercial-scale aquaponic urban farm in an industrial warehouse in east London (Figure 12). The 762 m2 growing space could produce more than 20,000 kg of salads and herbs (enough for 200,000 salad bags) and 4000 kg of fish each year. The unit closed down in 2017, since the comparatively small volume of produce did not make the business profitable.
Figure 12: Unit 84, London https://www.growup.org.uk/gallery/62tsypmu00xml48fks0sjme3rhdg2s
Edenworks in New York grows microgreens using four tiers of stacked DWC beds in a windowless warehouse. Their ready-to-eat microgreen mixes – broccoli, red cabbage and Russian kale, and radish, red cabbage and mustard greens – are sold in local grocery stores while the tilapia are either donated to local organizations or served at company events. Edenworks has also developed the ‘Farmstack’ system for rooftop greenhouses. The 75 m2 prototype system is located on top of an industrial building in Brooklyn (Figure 13). The water from the tilapia fish tanks located at the bottom of each 3 metre tall stack is pumped up to the top, and then filters through the different levels and back into the tank.
Figure 13: The Edenworks aquaponic rooftop greenhouse https://viewing.nyc/edenworks-rooftop-aquaponic-farmlab-uses-tilapia-fish-to-grow-fresh-produce/
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