Vertical farming is a new and innovative approach to agriculture that utilizes modern technology to address the challenges posed by increasing population, declining resources (water, soil, fertilizer), and changing climate conditions. In this method, crops are grown in a closed building, arranged vertically in levels and under controlled light, climate, and nutrient conditions. This approach is gaining traction as a potential solution to the current agricultural crisis (SharathKumar et al., 2020).

The technology of vertical farming can be classified under the umbrella term “indoor farming,” which describes agricultural cultivation in closed environments. However, this approach is not completely new. One form of indoor farming, the cultivation of mushrooms and chicory, has been used for decades with great success. Particularly the cultivation of mushrooms has been carried out in vertical levels for a long time to make efficient use of space in closed environments. The difference with novel vertical farming approaches is the use of lighting systems for controlled illumination of plants that require light (for photosynthesis) and very specific climate conditions as well as nutrient solutions for efficient growing. All these factors, meaning the right light intensity, nutrient solution composition, pH of the nutrient solution and climate condition have to be perfectly controlled simultaneously to really get a sufficient yield of the grown plants (Al-Kodmany, 2018; Plant Factory, 2016).

In vertical farming, hydro cultivation methods are used. This means that the nutrients are solved in water which can then be absorbed via the roots. Currently, there are two main sub-technologies: hydroponic and aeroponic systems. In hydroponic systems, the plant roots are in direct contact with the nutrient solution. In aeroponic systems, the roots are sprayed with the nutrient solution using a misting device. The roots hang freely in the air. Aeroponic systems have the advantage that the dissolved oxygen in the nutrient solution is not a limiting factor for growth. However, the use of misting devices is an additional energy source, generates heat, and requires additional technical effort. Aeroponic systems are also critical, for example, during power outages (Plant Factory, 2016; SharathKumar et al., 2020).

The lighting of hydroponically cultivated plants in vertical farming is now carried out with highly efficient LEDs to reduce the energy input of vertical farms. Nevertheless, the energy expenditure for lighting is still an unsolved problem. On the one hand, an alternative lighting method is used instead of the freely available sunlight, which by itself means additional energy generation. On the other hand, the light energy used for photosynthesis is only a fraction of the emitted light energy that is provided by the LEDs. In addition, the plant density per illuminated surface is still a very limiting factor. This is particularly evident in the cultivation of lettuce: a fully grown lettuce plant requires a much larger illuminated surface area than a lettuce seedling. What should you do? Giving the lettuce the final surface area right from the beginning and waste loads of unused, “unnecessarily illuminated” area? Since the growth of the salad as a function of time proceeds exponentially, it will only be efficiently illuminated in the final phase. Or implement the plant several times via the growing procedure? If this is done by people, contamination is a danger. And not the same danger as in nature: if a vertical farm is contaminated once, the whole production has to be stopped, cleaned and the plants will die. Automatic implementation can be an option, but this needs quite high mathematical power to accurately estimate the implementation cycle (remember: the growth of the salad as a function of time proceeds exponentially) (Saad et al., 2021; Santini et al., 2021; SharathKumar et al., 2020).In conclusion, while vertical farming offers many potential benefits, including reduced use of water and fertilizer, decreased land usage, and the ability to grow crops in urban areas, making this approach “the future farming method” remains a major challenge, especially for products requiring photosynthesis. Further research and development are needed to address this issue and make vertical farming a truly sustainable agriculture method.

Bachinger Emanuel

References

Al-Kodmany, K. (2018). The Vertical Farm: A Review of Developments and Implications for the Vertical City. Buildings, 8(2), 24. https://doi.org/10.3390/buildings8020024

Plant Factory. (2016). Elsevier. https://doi.org/10.1016/C2014-0-01039-8

Plenty. (2023). Farm Gallery: We Built Our Farm Around Our Plants. https://www.plenty.ag/farm-gallery/

Saad, M. H. M., Hamdan, N. M., & Sarker, M. R. (2021). State of the Art of Urban Smart Vertical Farming Automation System: Advanced Topologies, Issues and Recommendations. Electronics, 10(12), 1422. https://doi.org/10.3390/electronics10121422

Santini, A., Bartolini, E., Schneider, M., & Greco de Lemos, V. (2021). The crop growth planning problem in vertical farming. European Journal of Operational Research, 294(1), 377–390. https://doi.org/10.1016/j.ejor.2021.01.034

SharathKumar, M., Heuvelink, E., & Marcelis, L. F. M. (2020). Vertical Farming: Moving from Genetic to Environmental Modification. Trends in Plant Science, 25(8), 724–727. https://doi.org/10.1016/j.tplants.2020.05.012

Image Source: A vertical farm from Plenty® (Plenty, 2023)