There are supermarkets that grow their vegetables on the roof and buildings with facades set up as vertical farms. Urban gardening has become a new trend, both in a sociocultural and architectural sense. The steady rise in population growth is forcing us to rethink our paradigms. Yet, can urban farming really replace conventional farming?
We live in the century of cities. 55 percent of the world’s population is already living in urban areas. In Germany, the number is now over 70 percent. The population is steadily rising. The United Nations has estimated that by 2050, the global population will stand at nine billion people, and around two-thirds of them will live in urban agglomerations and megacities. And all of them want to be fed. Yet, the oceans have been almost depleted of fish, climate change threatens harvests, and animal feed, biofuel, and food crops compete for farmland. Food products have to be transported to cities. This fact alone results in people being alienated from their food, both literal and metaphorical. There are many stages before a food product reaches the consumer, including harvest or production, distribution, and sales. Not only does essential information about the groceries on the shelves get lost, but supermarket products are decoupled from a real feeling for these foods, their nutritional value, and their availability.
Nonetheless, more and more people are interested in a healthy lifestyle and inquire about the origins and value of the products that they consume. A lack of transparency in the food industry has led to growing skepticism towards large corporations, and many consumers dream about growing their own vegetables. Until recently, this option was only open to farmers or those owning a garden. In response to this dilemma, a trend has gradually developed that offers various ideas for enlightened consumers while also providing solutions for the increased demand for food.
From public park grounds to guerrilla gardens on derelict plots of land, urban gardening, with its wildly romantic, individually planted raised beds, has firmly established itself and ultimately developed into urban farming, namely the cultivation of fruit and vegetables in urban areas. This movement by no means represents a step backward in civilization, but it is rather an attempt to optimize the culture of urban living and offers a logical response to rotten meat scandals and tasteless greenhouse tomatoes.
In this respect, it is worth noting that already in the 1970s, Cuba’s state-sponsored agricultural system pursued the goal of achieving food self-sufficiency for people in impoverished residential areas. Today, two-thirds of all vegetables consumed in Havana come from gardens on the outskirts of the city. Similarly, the community gardens that arose in the 1970s in New York’s deprived neighborhoods are now regarded as essential forerunners of urban farming. The project, however, had a completely different incentive. To lower the crime rate in the Bronx, community groups were formed to transform vacant lots into gardens and vegetable beds, thereby bringing people together and engaging them in meaningful activities.
Since the 1990s, another idea arose for unused spaces that were neither suitable for demolition or construction – to convert them into public recreation areas. This led to park walkways such as the Coulée Verte René-Dumont in Paris, which served as the model for the High Line in New York. Other examples include using the grounds of the former Berlin Tempelhof Airport as a public park and London’s swimming pocket park facility on the Thames, both providing more green space in their respective cities.
The chronic lack of space in cities has given rise to creativity on the part of urban agriculture. Various sub-categories have emerged, such as rooftop farming, where flat roofs serve as cultivation space for crops, and vertical farming, whereby plants are not grown on a single level plane but rather cultivated on several vertically staggered surfaces, arranged one on top of each other, such as on the facades of buildings. Dickson Despommier has been researching this field at Columbia University in New York for close to 40 years. The scientist is regarded as a visionary in urban agriculture. He predicts that the future of agriculture lies in both vertical and soil-free cultivation. Despommier’s book on the subject is titled Vertical Farm: Feeding the World in the 21st century. “The idea of growing crops in hanging pots or even in water, as opposed to on the ground, is nothing new,” stresses Despommier in interviews. “You can cultivate almost any crop in a nutrient solution instead of soil. The only reason why we haven’t pressed ahead with this technology so far is that there has been no real need. Today, however, we find ourselves in a crisis due to climate change and the scarcity of resources.”
Already some 2600 years ago, the legendary hanging garden of Babylon was laid out on terraces and nourished by a sophisticated irrigation system. The basic idea is simple – plants do not actually require soil, but rather nutrients, air, and water. Soil-free or so-called hydroponic systems are easy to maintain and require much less water (only 5% compared to conventional cultivation systems). The constant water movement results in plants growing three times faster, principally because their roots do not have to search for nutrients in the soil, as they are continuously drenched with water rich in nutrients and oxygen. Hardly anything can go wrong, as once the seedlings are immersed in the cool nutrient solution, they take care of themselves. Also, by stacking the growing tanks above each other, the floor space for cultivation increases many times over. Fertilizer is produced from natural resources but differs in how it is processed. At present, the choice is between mineral (synthetically produced) or organic fertilizers. Many plants and systems can even make do without fertilizer.
Although hydroculture does not currently compete with traditional agriculture, its popularity and potential have not remained unnoticed. Soilless technology has given rise to an increasing number of so-called urban mini-ecosystems. An illustrative pioneer in this respect is the Dizengoff Center in Tel Aviv. Located on the roof of the oldest shopping mall in Israel in the center of this enormous city, it is a unique farm, where native crops, insects, and fish coexist since 2015. The rooftop farm produces more than 10,000 heads of lettuce each month and cultivates 17 different sorts of vegetables and herbs. A tight-knit mesh protects the facility from air pollution, the level of which is regularly tested in laboratories. The farm even features a banana tree, a beehive to provide biodynamic pollination, a bat cave, bird nests, and its own biogas system that transforms organic waste into gas, which is used for cooking and operating generators.
The farm employs a variety of vertical and horizontal hydroponic and aquaponic systems, whereby vegetables and fish are grown in a closed loop. Excrement from the carp, goldfish, and koi bred in the system is pumped into the vegetable water bed as fertilizer. The plant purifies the water, and it flows back into the aquarium. The use of pesticides is unnecessary, as the lack of soil prevents pests from infiltrating the system. Nonetheless, the products are not allowed to be called organic, as the organic seal in Israel requires crops to be grown in soil – an outdated principle that should be reconsidered.
“The main goal is to bring agriculture to the center of the city,” says Yoav Sharon from Green in the city, the rooftop garden initiative on the Dizengoff Center, which for the past five years has proved that the idea works. The farm now supplies 15 restaurants in Tel Aviv, and various market stands in the mall. Vegetables harvested with their roots are extra fresh and last significantly longer than conventional vegetables, even without refrigeration. These first urban farms are meant to demonstrate the advantages of urban, independent, and sustainable agriculture and encourage imitation, such as through workshops for the public. Both efforts have borne fruit. Many city dwellers have acquired their own plant cultivation system and have become self-sufficient growers. And there have since been several projects all over the world emulating this success.
Almost every large city boasts of a new farmscraper or rooftop garden, including such cities as Den Haag, Detroit, Chicago, Shanghai, Sydney, and Singapore. Some even filter their so-called greywater (wastewater from showers and dishwashers) for vertical gardens, such as in Santalaia in Bogotà. In Philadelphia, a supermarket chain cultivates produce for their stores with hydroponic systems directly on their roofs, thereby saving enormously on transportation costs. In France, the largest urban vegetable farm in Europe is to be built on the Paris Expo grounds, occupying some 14,000 square meters. In Berlin, a company called Dachfarm Berlin focuses on building-integrated agriculture and urban nutrition strategies, coming up with solutions for almost every architectural situation. All in all, this is a desirable competitive situation that is already approaching its limits. There were plans in the Netherlands to construct a closed-loop system in which pigs and laying hens would be raised on specially designated floors of a building to provide fertilizer to a rooftop farm. Fortunately, the project was rejected as a result of opposition from the local population.
Yet, even without direct benefits, vertical gardens make sense. They dampen urban noise and purify the air by producing oxygen and binding fine particles and CO2. The French garden architect Patrick Blanc, whose designs have included a botanical facade artwork for the Berlin cultural department store Dussmann, has been arguing this point for the past 30 years. Researchers have supported his claims. A similar response to climate change has been provided by the architect Christoph Ingenhoven with his latest project – the recently completed Kö-Bogen II commercial and office building in Düsseldorf. Its exterior walls have been planted with 8 kilometers of hornbeam hedges and are now Europe’s longest green facade. Of course, points of criticism can be laid here as well, seeing as how it will take a few years before the green system has paid for itself, also in terms of emissions. But this doesn’t mean the direction is wrong.
One of the most exciting projects is the yet to be realized Farmhouse by the Studio Precht in Austria. It features modular, honeycomb-like residential units stacked endlessly on top of each other and are designed so that each apartment has access to its own or a public garden. Produce is cultivated and harvested on every floor. Each unit can be uniquely designed and thereby has the character of an individual townhouse. Refuse is recycled and treated, while wastewater is filtered. With its self-sufficiency strategy and passive energy management, the Farmhouse provides a dual contribution to the environment. But it goes far beyond just this. The project stresses active participation and co-management, as well as the question of what we eat. And today, this is a political decision.