Vertical farming and the challenges of horticultural lighting
The Food and Agriculture Organization (FAO) of the United Nations projects that global agricultural production will need to increase by 50 percent in order to meet the food requirements of a projected world population of almost 10 billion by the year 20501. Yet, the available land suitable for farming and other agricultural activities is finite, and has actually declined in recent decades, from nearly 40 percent of the world’s land area in 1991 to just 37 percent in 20152.
Fortunately, innovative agricultural techniques such as controlled environment agriculture (also sometimes referred to as vertical farming) hold significant promise as a mechanism to increase overall agricultural production to address local or regional food needs and to help bring fresher and more nutritious food to billions of people, all while reducing the environmental impact associated with conventional farming techniques. But the successful deployment and operation of vertical farms depends on the effective use of several key technologies, including state-of-the-art lighting systems and products, as well as regional acceptance and suitable regulations.
In this article, we’ll discuss the important role of artificial lighting in plant growth in vertical farming installations, some of the potential food safety issues related to vertical farms, and how performance testing of horticultural lighting products can help support the expansion of vertical farming efforts.
What is vertical farming?
Although often used interchangeably with the more generic term “indoor farming,” the term “vertical farming” generally refers to a farming technique in which plants are grown in vertically-stacked planting beds stored in a controlled, indoor environment. Depending on the height of the vertical stacks, spacing between the tiers, and the number of planting beds in each stack, a vertical farm produces yields that far exceed that of a comparable horizontal land area. This approach can not only help to increase production from currently available agricultural land but can also be successfully deployed in dense urban areas where space is at a premium.
In general, vertical farms rely on soil-based or hydroponic solutions, which can use a customised combination of minerals and other natural nutrients consistent with the requirements of a given plant. Other solutions with the potential to further enhance resource efficiency are aeroponic techniques, in which a nutrient solution is sprayed on free-hanging plant roots, or aquaponic grow systems which combine a plant growth system with a fish cultivating system. This all but eliminates the need for chemical fertilisation, reducing the accompanying chemical runoff that can occur. And, compared to traditional cultivation techniques, the use of a controlled or protected environment which focuses on resource-conserving methods can significantly reduce overall water usage and waste.
Some vertical farm concepts do not rely on natural sunlight, which makes artificial lighting essential. This is in general the case in areas where sunlight is scarce, e.g. in the northern hemisphere during the winter months, or where access to sunlight is restricted, such as in densely-structured urban areas. In particular, light-emitting diode (LED)- based lighting systems are highly customisable, providing indoor farms with a wide range of light color and light intensity combinations to match the unique requirements of an individual plant.
In a highly-controlled indoor environment, the application of plant-specific nutrients and optimal lighting conditions can significantly increase the yield of vertical farms or add value to the plants by influencing their nutritional quality, taste and appearance. Because the cultivation environment is tightly controlled and not subject to variations in climate or extreme weather conditions, vertical farms allow for year-round farming and multiple planting “seasons,” thereby dramatically increasing a farm’s total annual yield and reducing crop failures.
Key factors in vertical farms
Photosynthesis is the process by which plants convert light energy into chemical energy. Artificial light sources designed to influence plant development are often referred to as plant light, growth light or horticulture light. Unlike LED lighting systems used for industrial or commercial applications, LED luminaires used for plant growth must satisfactorily address a variety of performance and safety factors to help ensure that vertical farms achieve their optimal agricultural output without harming the surrounding environment or workers operating the installation. These factors are discussed in greater detail in the following sections.
Plants are influence by a number of parameters such as ambient temperature, water quality and lighting conditions. Controlled environment farms are designed to control parameters such as temperature and humidity in order to provide the optimal growing conditions for plant cultivation. Furthermore, the form factors (type and dimensions of growing installation and spacing between plants) can also be used to optimise that growth, and can vary between plants, e.g. leafy greens and herbs will require less vertical spacing between the tiers of a vertical rack compared to flowers or fruit plants.
Lighting systems should also evaluated for to their heat management characteristics, and be designed to mitigate the heat they generate in order to reduce any potential negative impact on growth, while also allowing sufficient air circulation and ventilation. Where feasible, considerations can also be given to mechanisms for recycling any excess heat generated by lighting, as well as excess moisture produced through the farming process.
The unique environmental conditions of vertical farms also pose a number of reliability challenges for manufacturers of horticultural lighting systems. For example, high temperatures and humidity levels can lead to moisture and particles penetrating the light casing, increasing the risk of electrical stresses, damage to device drivers or the corrosion of essential components. This can lead to premature device failure or comprise the specified quality of the emitted light.
In many vertical farms, separate systems that provide light and water are likely to be in close proximity to one another, creating a potential risk of electrical shock to horticulturalists and other workers. More important, the potential biological effects of LED emission spectrum, e.g., Bluelight hazard and glare, have long been a concern. The concentrated presence of potentially thousands of LED lights in a single vertical farm may create important health and safety concerns for vertical farm workers.
It is important to note that, though food produced through vertical farming techniques may be safer to consume than conventionally-grown food products, hazards can still be introduced during the growing process. Such hazards might include dirt and bacteria from workers, chemicals hazards in the nutrient medium and water cleanliness and safety, as well as post-farm handling activities including sorting, trimming and transportation. Therefore, food safety management tools like HACCP and food safety evaluation and testing are as important in vertical farming as in conventional agriculture practices.
Perhaps the most important factors involve the specific performance parameters of the selected lighting systems and products. To be successfully used in vertical farming applications, the output of individual lighting systems must conform with the specialised lighting “recipe” that meets the unique growing requirements of the planned agricultural products. At a minimum, this approach can provide for more effective plant development compared with that achievable through the use of conventional light sources but, when optimized, can promote photosynthesis and increase the health of the grown produce. Increasingly, lighting manufacturers and farm operators alike understand that the testing and validation of these performance characteristics is essential in selecting lighting systems that best meet the growing requirements of a given vertical farm.
How TÜV SÜD can support
TÜV SÜD has worked closely with some of the leading luminaire manufacturers as well as major participants in the vertical farming industry to help ensure that horticultural lighting systems conform with the unique and demanding requirements of vertical farming applications. In addition to serving as a single source for testing and certification of all types of lighting systems and products in accordance with all applicable electrical safety regulations and standards, we also conduct customer-specific testing to assess performance, functionality and durability consistent with end-use requirements. TÜV SÜD experts also have the requisite expertise to measure lighting products for compliance with lighting parameters in the photosynthetic active radiation (PAR) range used for plant growth, such as photosynthetic photon flux (PPF) and photosynthetic photon flux density (PPFD).
For more information about TÜV SÜD’s horticultural lighting solutions, contact us at [email protected], or go to our Food page.
 “The future of food and agriculture: Trends and challenges,” a report by the Food and Agriculture Organization of the United Nations, 2017. Available here (as of 24 March 2018).
 “Agricultural land (% of land area),” data from the FAO as reported by The World Bank, 2018. Available here (as of 24 March 2018).