Gardening in the city: anyone can be a farmer

D.The future of agriculture lies at the heart of the Ruhr region, on the roof of the Oberhausen employment center. On the fifth floor, in a modern greenhouse, berries, herbs and lettuce grow. The harvest is impressive: 100,000 heads of lettuce, 200,000 pots of aromatic herbs and 500 kilograms of strawberries grow on 940 square meters every year. “They are sold on the occasion of the ‘Open Roof Garden Days’, to local restaurateurs and a catering company,” says Elita Wiegand, spokesperson for the project co-initiated by the city.

The operator of the roof garden is the Brandenburg company Exner Grüne Innovation. “Providing food to people in cities will be a challenge in the future because cultivated areas are limited,” says company head Wolfgang Grüne.

The Greens are convinced that at least part of agricultural production must be relocated to the city, also to promote climate protection: “Growing in cities conserves resources because transport routes are much shorter and CO2 consumption is lower” .

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The Oberhausen experiment aims to demonstrate that part of the world’s food can also be guaranteed in cities. There are currently 7.96 billion people on earth and the United Nations predicts that there will be 9.7 billion in 2050. Added to this is continued urbanization: more and more people around the world are moving to metropolitan areas. Mini gardens in the middle of densely populated residential areas would be a solution to replenish them. Thanks to new technologies, even every normal resident can now grow fruit and vegetables at home in their own apartment.

The method used by the company on Oberhausen’s Altmarkt is called hydroponics. The word is made up of the Greek terms for water (hydro) and work (ponos). The roots of the plants are hung in a nutrient solution that provides them with the necessary minerals.

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“As a result, herbs and leafy vegetables grow faster,” says Grüne. “We can harvest heads of lettuce in just 5-8 weeks.” The method also saves water. To grow a kilogram of tomatoes in the ground in a field it takes 400 liters, with the hydroponic method it is only 70 liters.

In Germany, some manufacturers offer smaller indoor gardening systems, while in the United States, soilless cultivation in the suburbs of large cities is already an independent branch of the economy. AeroFarms in New York alone increased sales of farm products produced in buildings last year from 2.5 to nearly four million US dollars. Publicly traded competitor Appharvest posted sales of over $ 8.9 million in 2021.

Gardening technology for space

Both benefit from a NASA project. The US space agency has perfected the cultivation method to ensure the supply of astronauts and scientists on the International Space Station ISS. The start-ups then picked up on the idea and started growing lettuce, vegetables, and berries at Detroit’s former auto plants.

One of the startups started Planted Detroit, a vertical farm located in a warehouse in the Port and Industrial District on Lafayette Street. Your customers are organic shops, weekly markets and restaurants. “We collect our plants every day and ship them within hours,” says Tom Adamczyk, founder and CEO of Planted Detroit.

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Günter Vornholz is convinced that urban agriculture can also breathe new life into empty industrial buildings in Germany: “There are thousands of unused former factories in the country, not all of which are destined for demolition, but for which it is not worth turning them into offices or residential buildings, ”says the professor of real estate economics at the EBZ Business School in Bochum.

In Herne, Exner Grüne Innovation is currently converting an old nuclear bunker into a vertical farm. And Irish investor Greenman wants to erect two greenhouse towers, each nine meters high, in a Berlin business park for his Greenman Open fund. “We want to create one of the most sustainable vertical farming systems in Germany,” says Mario Gatineau, CEO of Potager Farm. The Greenman subsidiary is said to manage the towers. He wants to grow parsley, chives, basil, and leafy greens like arugula and mustard leaves to sell fresh every day in retail park supermarkets.

Home-made indoor garden

Hydroponics is also gaining importance in private homes. For Swiss software developer Danilo Bargen, hydroponics is “one of the simplest ways to grow lettuce or spices at home in a rather dark apartment,” he writes on his blog about new technologies. All you need is an LED grow light that emits blue light in the spectral range of 400 to 490 nanometers and red light in the range of 640 to 700 nanometers.

In addition, a container for the nutrient solution and an attachment with holes through which the roots of the plants can absorb the nutrient solution. Bargen reckons that such a six-head lettuce grow set can be built on its own for under $ 60.

If you want to make things easier for yourself, you can use the Kratky method, explains biotechnologist Harry Pilawski, who runs the Internet portal In the process developed by the US biologist Bernard Kratky, the container for the nutrient solution is first lined with expanded clay and then filled. The low-lime clay absorbs the nutrient solution and then constantly releases it to the plant roots.

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“While the nutrient solution is constantly being refilled with any other hydroponics, this is not necessary with the Kratky method,” says Pilawski. The more the aqueous nutrient solution is absorbed by the plants, the greater the space between the substrate and the surface of the water becomes: “This provides the plants with enough minerals and at the same time oxygen for the roots.”

Even large suppliers have now entered the business of hydroponic systems for the occupants. Bosch Siemens Hausgeräte (BSH) launched a “SmartGrow” series in 2018. With SmartGrow Life measuring 33 by 17.5 centimeters at a price of 170 euros, it is possible to grow more than 50 different herbs, salads and edible flowers. Small light diodes produce daylight. A magnetically coupled pump constantly displaces the nutrient solution, which only needs to be renewed every three weeks.

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Growing plants with hydroponic systems in your own home “has transformed from a niche topic into a trend that is attracting the interest of an ever-growing group of buyers,” says Franziska Knöckelmann, a spokesperson for Bosch. Many customers simply wanted to know the technology as well.

The latter coincides with the experiences of Oberhausen. “Many visitors come first to learn more about the growing method,” says the spokesperson for the Wiegand project. “Then they buy the herbs and salads with even more enthusiasm.”

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