By 2050, there will be 9 billion inhabitants on earth, with 80% living in an urban environment. Even with the anticipation of certain technological developments, traditional agriculture will not be able to meet the demand for food. In fact, 80% of all the arable land on the planet is already being exploited. By 2050, the shortfall in the land area required to feed mankind will be equivalent to an area the size of Brazil. The limitation on available cultivable areas has forced agricultural engineers, architects and designers to invent a new concept: the vertical urban farm!
The idea is simple: to produce large quantities of food produce in structures occupying a reduced unit area of land, e.g. tower blocks. Dickson Despommier, professor of environmental sciences at Columbia University in New York, was the first to formalise the vertical farm concept in 1999. With the technologies available at the time, he maintained that a vertical farm of 30 storeys, constructed for a sum of 84 million dollars, could feed 30,000 people with a yield 5 to 6 times greater than that of traditional agriculture.
Anything or almost anything can be produced in these skyscraper gardens of the future: not only cereals, fruits and vegetables, but also pigs, cattle, fish… And this project is far from utopian given the technological advances made in the area of growing crops under glass. Soil-less methods of crop production, of the hydroponic type, have already proved themselves in many greenhouses throughout the world. Hydroponics consist of replacing the soil with an inert neutral substrate (such as sand, clay pellets, rockwool, etc.), regularly irrigated by a liquid medium, which provides the plants with mineral salts and essential nutrients. The installation of a drip irrigation system is, therefore, recommended. There are other methods such as aeroponics. This is one of the latest developments of these techniques and also one of the most sophisticated. The roots of the plants are not in contact with a solid medium, nor even a liquid medium: They are mist sprayed with a nutrient-rich liquid via an atomiser.
"Anything or almost anything can be produced in these skyscraper gardens of the future: not only cereals, fruits and vegetables, but also pigs, cattle, fish"
Apart from occupying very little ground space, this farm of the future offers many advantages:
Crops are not affected by the vagaries of the weather, offering, on account of the optimal conditions, yields that are 5 to 6 times higher than open field crops.
The controlled environment of these towers also allows for considerable savings to be made on water use, compared with traditional crop methods: since the irrigation systems operate on a closed circuit basis, the crops produced in this way use far less water. Despommier envisages recovering the water vapour produced by the evapotranspiration of the plants. Moreover, local urban (waste) water will be recycled and used for the irrigation of the crops.
The urban farm is designed in such a way that it does not need chemical fertilisers. By giving the plants what they need when they need it, the crop requirements are greatly reduced as far as insecticides, herbicides and other chemical fertilisers are concerned. Furthermore, by composting the material food waste of the local community, Despommier aims to transform this into organic fertilisers that will be directly usable for these fruits and vegetables. In this sense, Lavoisier’s famous saying more than ever applies: “nothing is lost, nothing is created, everything is transformed”.
There is another advantage: producing food directly at the place of consumption means that less storage and transportation is required, which are heavy consumers of fossil fuels. That contributes towards reducing the emissions of CO2 into the atmosphere. The presence of plants in the city centre also improves air quality, since the plants take in CO2 and release oxygen into the atmosphere.
Despommier also foresees these farms becoming self-sufficient in energy, with the installation of photovoltaic panels or wind turbines on the structure of the building.
"By giving the plants what they need when they need it, the crop requirements are greatly reduced as far as insecticides, herbicides and other chemical fertilisers are concerned"
Despommier’s vertical farm concept has been taken up by many architectural firms around the world. In France, architects of the SOA agency initiated the “living tower” project in 2006, motivated by a competition launched by the city of Rennes. This project, from the point of view of sustainable development, goes even further than Despommier’s. This living tower even incorporates 11,000 m2 of living accommodation and 8,600 m2 of offices, while preserving record production capabilities: more than 63 tonnes of tomatoes, 9 tonnes of strawberries and 40,000 lettuces per year, amongst others. It is also completely self-sufficient in energy, supplied by two wind turbines and 500 m2 of photovoltaic (PV) cells!
On paper, this urban farm concept seems ideal but it does raise a certain number of concerns: can the energy requirements associated with lighting and heating be fully guaranteed by renewable energy sources? Is there not a risk that new diseases or parasites will emerge with this new method of crop production and stock breeding? What will happen with the substrate and plastic trays used for soilless crop production? Finally, there is the problem of financing. How can institutions be found that are willing to finance these projects and how will it be possible to make these farms profitable, with their cost running into millions of euros?
Only the implementation of a prototype vertical farm will provide us with the answers to these questions. This has been achieved in Singapore. In October 2012, Sky Green officially began operating commercially and is now considered to be a real farm, in the true sense of the word, of 3.65 hectares, located at Lim Chu Kang. Half a tonne of vegetables are produced every day for local distribution. They fetch prices 10 to 20 cents higher than the normal price per kilo, but that hasn’t put anyone off - on the contrary, demand is on the increase.
Other prototypes are about to rise from the ground in Korea, Japan, Sweden, U.S.A. and Holland.
Furthermore, smaller, economically viable urban farms already exist on the other side of the Atlantic. Supermarkets and restaurants, which are the points of sale of agricultural products processed in a varying degree, have developed fruit and vegetable gardens on their roofs. An iconic example in this respect is Eli Zabar’s bakery and farmers market in Manhattan. Since 1995, greenhouses located on the roof of the shop roof have been supplying it with tomatoes, fresh berries, figs, etc… In Montreal, Lula farm sells lettuces, cucumbers and tomatoes grown on site, in a vast greenhouse installed on the roof of an apartment building in the Ahunstic Cartierville eco-district.
Dick Despommier is confident. According to him, the concept of urban farms responds to a genuine trend in society. The demand for urban agriculture is growing all the time. In Montreal, a law compels new administrative and institutional buildings to have an agricultural roof. The property developers are being inundated with applications for kitchen gardens from local inhabitants. As far as homeowners are concerned, hydroponic kits are currently being developed for the installation of mini farms at home. These are all signs that have convinced Dick Despommier to forecast, “Vertical farms will be commonplace in thirty years time.”