The term Vertical Farming (VF) can be used to define a variety of concepts. For some, it might conjure up images of tall structures with plants growing on the outside, while others may imagine multiple racks within shipping containers. In essence, VF refers to the practice of building upwards, or downwards in the case of underground setups, to maximise production area for a given footprint.
Vertical farming can offer a practical solution in places where space is limited or land value is high, such as in cities, or where conventional greenhouses would not be viable, perhaps due to space or climate. It may also be possible to create a vertical growing setup within a conventional greenhouse, if an arrangement of layers can be set up adequately, without compromising crop quality, although the height of the structure could limit what is practical.
As vertical farming establishes itself as a viable alternative to traditional methods, sustainability is really the key. Building vertically not only saves space but can also allow unconventional spaces, such as underground tunnels, to be used for growing. Additionally, VF has also been demonstrated to reduce the amount of soil and water required, with many using hydroponics, making it an option in arid regions where conventional glasshouses are not viable.
An important consideration for vertical farms is to ensure sufficient light reaches all layers of the crop. Even if using daylight, shading of the lower layers, especially in built-up areas, will reduce the amount of light reaching the crop. Most VFs will require supplementary lights; a light fitting above each layer of the crop is likely to be necessary.
Growing Underground, a London based setup, uses a hydroponic system to grow microgreens on four levels in 500m2 of tunnels 33 metres underground. With no natural light, high-efficiency LEDs are vital to give the crop the light spectrum it needs, but these still consume a large amount of energy and produce a considerable amount of heat. Chris Nelson from Growing Underground says, “the aim is to become carbon neutral, but it is still an energy intensive business. With closely packed layers, it is easy for a microclimate to form, so it is important to have good, effective climate monitoring and control to ensure sufficient air movement and to maintain an optimum growing environment.”
Fully enclosed farms (i.e. with no windows) demand complete control over the environment. While the number of external factors is reduced, it can also be expensive, as there is no access to free daylight. This could be an interesting option for anyone with access to an underground space, but “a clear business case is crucial” warns Chris Nelson.
The temperate UK climate means conventional glasshouses work well; heating demands can be met easily and light levels are usually acceptable. As such, vertical farms have typically been aimed at supplying niche markets: low volume, high value. Vertical farming may not appear to be the ‘greenest’ solution compared to crops grown under glass in warm, sunny climes at first, but it does allow produce to be grown close to market. As such, food miles can be drastically reduced.
A self-contained setup lends itself well to consistent, year-round production with a quick turnover time. A closed system, i.e. with water and nutrient recycling and heat recovery from vented air, can help improve efficiency, but disease control is vital. Careful climate management is necessary. Depending on the location, vertical farms often need a significant amount of heating or cooling, as well as some form of humidity control. Air movement is also important to maintain an active climate. All of these will use energy and contribute significantly towards operating costs, but sustainable, local food production is a benefit in itself and offers a degree of security against the myriad of factors that can adversely affect conventional production methods.
Although VF may not yet drastically reduce the industry’s environmental impact, in the UK at least, it does offer a solution to food production in areas where conventional methods just would not work. This is one of the main drivers behind VF, which can help combat the need to produce more food for an ever-expanding world population.
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