Press release | 29 July 2021 | sn

Growing Food in the City in Small Spaces and Within Easy Reach

Vertical vegetable cultivation using mobile hydroponic farms

Using conventional methods to supply Berlin’s 3.6 million residents with lettuce all year round would require a land surface of 836 hectares. This is more than twice the space taken up by Berlin’s biggest city park, the Tempelhofer Feld. However, if the lettuce is grown on a vertical hydroponic farm, then only 38 hectares of land are required – barely a tenth of the Tempelhofer Feld. This is a modelled projection by Dr. Grit Bürgow and Andreas Horn based on the first year of operation of their mobile vertical hydroponic farm “Shower-Tower 61” covering an area of two square meters.

Since early summer 2020, TU Berlin together with its partners from the research project “GartenLeistungen” have been operating the vertical hydroponic farm “Shower-Tower 61” as a real-world laboratory. It is located at the beach volleyball facility “Beach61” in Gleisdreieck Park, not far from Potsdamer Platz. TU Berlin students had originally built the farm’s prototype as part of the project workshop “Roof Water-Farm tu-project” that Dr. Grit Bürgow led jointly with student coordinator Andreas Horn and architectural student Gabriel Sigler. Hydroponics is a type of horticulture in which plants are grown using nutrient solutions alone – without soil.

Treated shower water is not harmful to health

Building on the pertinent research results that emerged from the Roof Water-Farm project, the further findings from the first season of operating “Shower-Tower 61” show that treated shower water – the solution used here to grow lettuce and herbs – can be used safely in food production. The new mobile reed bed covering ten square meters also functions as a climate module. It absorbs excess water from the shower-water treatment process, acting both as a kind of buffer and as a sponge for rainwater. Because of the reeds’ high evaporation capacity, up to 1,000 liters of water are evaporated per day over the whole of this surface area. This helps create a pleasantly cool atmosphere and represents a volume of water equivalent to almost twice Berlin’s annual rainfall. “Establishing such wetland greenery in public parks and urban open spaces would provide many advantages in terms of the design of the ecosystem and for the economy and society as a whole,” says Dr. Bürgow. It is a simple and inexpensive measure to prevent both droughts and flood-like heavy rainfall events in the city. Duplicating this design principle would produce not only a pleasant atmosphere, but also natural water reservoirs that would generate a temperate climate.

Community garden “himmelbeet” in the Wedding district of Berlin

In May 2021, TU Berlin began operating its second mobile vertical hydroponic farm in an urban surrounding, namely at the “himmelbeet” community garden in the Wedding district of Berlin. While the innovative aspect of “Shower-Tower 61” is its use of treated shower water, in the case of the “himmelbeet” community garden the TU scientists collect the rainwater that runs off the roof of the local café, enriching it likewise with nutrients and using it to irrigate the hydroponic farm. Lettuces and herbs like basil, but also cabbage varieties like pak choi and red kale, or beets like Swiss chard thrive magnificently in these vertical hydroponic farms. Both the “himmelbeet” café and the bistro belonging to the beach volleyball facility use the herbs and lettuces in their kitchens. “These small local islands of food supply within easy reach demonstrate the ecosystem services that such community gardens can provide for us humans,” says Dr. Grit Bürgow. Ecosystem services include provisioning services such as food production, but also regulating services for water, temperature or climate, as well as cultural services such as recreation or environmental education.

Covering the annual needs of 17 people

“For us, TU Berlin’s vertical hydroponic farm is exciting in all sorts of ways. It’s brought us into contact with the latest technology that, on the one hand, is extremely space-saving – and the question of the most efficient use of available space is never far from people’s minds in urban areas – and, on the other hand, we’re now finally able to realize our plan to use the café roof’s rainwater,” says Felix Lodes from the “himmelbeet” project. And he says that for all those people from the local neighborhood who use the community garden, the farm provides a low-threshold, hands-on opportunity to come into contact with science. Berlin’s ‘himmelbeet’ community garden contains around 300 raised beds. The cultivation area of 305 square meters yields about 1,660 kilograms of food per gardening season. Theoretically, this food, worth around 3,400 euros, should be able to meet the annual needs of 17 people. This is shown in the calculations of the Institute for Ecological Economy Research (IÖW), which is investigating the ecosystem services of gardens, parks and green spaces in its “GartenLeistung” project.

In the meantime, a start-up has emerged from TU Berlin’s project workshop “Roof Water-Farm tu-project”. Having successfully tested on his balcony a miniature version of the vertical hydroponic system, former TU Berlin tutor Andreas Horn has – together with Alexander Schirrmeister – founded the company “HydroTower”. They are driven by the idea that city dwellers can provide themselves with lettuces, herbs and vegetables even without gardens of their own.

The vertical hydroponic farms are part of the project “GartenLeistungen. Urban Gardens and Parks: Multidimensional services for socially, ecologically and economically sustainable management of urban areas and flows of materials” funded by the Federal Ministry of Education and Research. One of the goals of this project is to determine the benefits of gardens and parks for urban climate and biodiversity, as well as their ecosystem services to humans.