Sustainability of future urban food systems: Vertical Farming

While world population in cities is constantly growing, the realization of a sustainable development is increasingly becoming a matter of urban fabric, making crucial the realization of new food systems that could provide nutrition from city interior or outskirt. Indeed, for a long time food system has been considered a rural issue, most of the time ignored by architects and urban planners in cites design. To date, the concept of “edible cities” is getting more familiar to urbanists and evolving through the key role of Urban Agriculture (UA).

Urban Agriculture is a multifunctional practice that integrating cities food system could help achieving mutual benefits through the offer of numerous ecosystem services. The main benefits and services are related to food security, urban micro-climate management, carbon footprint reduction, social inclusion, income generation, education and citizens’ health. Despite UA could be performed on empty lands within and in the fringe of the city, competition for urban soil as well as risks connected to heavy metals contamination are requiring the improvement of soilless productive systems. With soilless farming is intended any method of cultivation without soil, also including hydroponic (plant growth in water), aeroponic (water nebulization on plants roots) or aquaponic (use of fishes’ dejections for plant nutrition) techniques. These systems, which may also be integrated inside (indoor farming) or on top (rooftop farming) of buildings, can present different technological complexity depending on framework of application, ranging from subsistence family gardens to technologically advanced business-oriented food enterprises.

The most high-tech form of UA is embodied by the Plants Factories, also mentioned as Vertical Farms. These farming systems are based on the control of all environmental factors that can affect plant growth, including temperature, relative humidity, light and CO2. Therefore, the production results completely isolated from outdoor conditions, adopting closed and thermally insulated cultivation chambers communicating with the external only for air exchange. This net separation is a primary quality of this form of urban agriculture, making the system completely resilient to outside extreme climatic conditions and diseases, contemporary allowing a non-stop yearly production free from pesticides. Another interesting implication of vertical farming is connected to soil consumption. Indeed, thanks to the possibility to cultivate on more levels, high quantities of product can be produced in less space, therefore reducing the current global concern for agricultural land consumption. Least, the great closeness to consumption centers determines reduced transport and storage, with overall benefit on carbon footprint.

The Vertical Farms apply an indoor technology to perform cultivation, usually explicated through the use of LED lights, hydroponic systems and sensors to control environmental factors (e.g., air temperature and humidity). Compared to other light typologies, LED technology present interesting qualities for the development of Plant Factories, particularly showing higher luminous efficiency, optimal spectra selection, low surface temperature, long lifetime and good cost performances. Besides, hydroponic is the best solution to adopt in vertical farming, consisting on a direct contact between plants roots and a nutritive solution, reducing substrates use and overall growing system weight. Furthermore, in the case of application of a closed system it can help water savings, achieving a water use efficiency 30-50 times higher than open-air or greenhouse production. Use of sensors also contribute to an easier management, especially of the root-zone where pH, electrical conductivity, oxygen and temperature can be kept under control.