‘Urban Farming’: Are rooftop fields the future?

Blueprint of a planned roof garden in Berlin. Up to two million square meters of roof space could be used for plant cultivation in Germany's capital alone. But the investment costs are still relatively high. [© Dachfarm Berlin]

This article is part of our special report New terminologies in sustainable food systems.

Large cities offer millions of square meters of unused roof space. Why aren’t they being converted to cultivate crops? The potential seems enormous, but “urban farming” is still in its infancy. EURACTIV Germany reports.

Salad from the roof of the supermarket or tomatoes from the facade of a high-rise building? What sounds like fiction is already reality in some cities, albeit on a small scale. Urban farming is not a new concept, but one that has hardly been exploited to date.

Cultivating fruits and vegetables could experience a boom in the coming decades. After all, the human population is growing rapidly and is increasingly settling in cities. More than half of this population is already living in cities, and by the middle of the century, around 66% of people are expected to be living in cities – out of a world population of 9.7 billion.

More food also means correspondingly more demand for farmland, but this already accounts for 42% of global land area.

Another problem is transport. According to the Fraunhofer Institute, around 12% of agricultural emissions are attributable to this alone.

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Urban gardens for times of crisis

Could urban farming be part of the solution? One thing is certain: The idea is not new. Until the 19th century, cultivating crops was common practice within cities. When they disappeared, private allotment gardens spread.

Interestingly, a new trend is emerging: self-sufficiency is booming in the city, especially in times of crisis.

Often with success, as the British example shows: During World War Two, the government launched the “Dig for Victory” campaign. As a result, up to 50% of fruit and vegetables were produced by the population in allotment gardens.

In Spain, during the economic crisis, the proportion of allotment plots and community gardens increased six-fold between 2006 and 2014.

Apart from private cultivation, however, there are hardly any places where agriculture takes place on a larger scale in cities.

Roof gardens of the future use domestic heat and rainwater

In Europe, urban farming is still in its infancy.

“Every morning, I ask myself why not many more cities invest in it,” says Jörg Finkbeiner, architect and co-founder of the Berlin network ‘Dachfarm.’ The consortium consists of gardeners, agroscientists and architects, who together plan greenhouses for growing crops in the city.

However, Finkbeiner believes that this cannot be the case with urban farming, because most buildings are not statically suitable for it: “If you put crops in tubs on a roof and water them, you can quickly achieve 300 kilograms per square meter. Most buildings can’t support that.”

Dachfarm, therefore, relies on roof structures that are as light as possible and are built on top of existing buildings. The plants grow either in substrates such as pumice, lava or compost, as these are much lighter than soil, or in hydroponic systems, where the nutrient supply is provided directly via a nutrient solution.

The glass gardens are designed to operate as efficiently as possible by using the waste heat from the building, collecting rainwater or recycling greywater from households.

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With Dachfarm, we want to show that the increasing amount of pavement in cities and the loss of arable land do not contradict themselves, Finkbeiner told EURACTIV.de.

Other advantages are that roof gardens can be used to produce close to the consumer and “on-demand,” so to speak, eliminating long transport routes or the need to store food. But not every type of agricultural cultivation is structurally possible, Finkbeiner points out. Besides, there are many open questions particularly in terms of building codes.

Bologna and Amsterdam with great potential

For supermarkets or restaurants, the own roof garden could be an attractive concept.

However, it is not worthwhile for everyone, because investment costs are still comparatively high and the food harvested in this way is more expensive.

A 2017 study by the European Parliament’s Scientific Service (EPRS) also came to the same conclusion: urban agriculture is “associated with considerable ecological, social and health benefits,” but can increase biodiversity and counteract the heating of cities.

However, this is also associated with high operating costs, for example for electricity, and is in competition with other types of use, for example for solar energy systems. In addition, the report says, tensions between “traditional and innovative farmers” and an increase in land values are also concerns.

There are no reliable figures on how widespread urban farming is in the EU. However, according to the ERPS evaluation, the potential could be huge, depending on the city.

In Bologna, for example, more than three-quarters of the vegetables consumed there could be grown in roof gardens. In Amsterdam, where currently only 0.0018% of food is produced locally, up to 90% of the fruit and vegetables consumed could be grown.

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Commission has no plans special funding

These figures seem optimistic, as they would probably require strong political support. In the current EU Common Agricultural Policy, urban farming projects can theoretically be financed with funds from both pillars as well as from the European Social Fund and the Regional Development Fund, but this is at the discretion of the member states.

Further support is not in sight, as the Commission “currently has no plans to coordinate strategies for urban agriculture beyond different levels of government,” according to the response EU Agriculture Commissioner Janusz Wojciechowski gave in the European Parliament in May.

However, a planning study on the topic is currently being prepared. This should be completed this autumn.

[Edited by Gerardo Fortuna/Zoran Radosavljevic]

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