CityTree Refurbished and Relocated
To mark the sixth anniversary of the CityTree’s installation in front of Deutsche Telekom’s headquarters in Bonn, the air filter has undergone a refurbishment to ensure that it can continue serving its purpose for many years to come.
“In line with our commitment to sustainability, our products are designed to be maintained and repaired with minimal effort”, says Peter Sänger, Managing Director of Green City Solutions. He adds: “We are aiming for a service life of at least 15 years – a goal that, based on the experience of the past six years of collaboration, is absolutely realistic.”
Photo: GCS
A Joint Journey Since 2020
From the outset, when the project was first installed in early June 2020, it was clear that the Bonn project was more than a one-off measure. At the time, we wrote that the CityTree stood “not only for another step towards the smart city of the future, but also for the beginning of a successful partnership”. Around the anniversary in June, it is clear – and tangible in the form of fresh air – how strong and long-lasting this partnership has become.
The fact that this project is rooted in Bonn is particularly fitting: Deutsche Telekom itself refers to the city as its “home” and thereby underlines its long-term commitment to the region. With “more than 12,000 people from Bonn and the surrounding region”, working “for Deutsche Telekom in the former capital” and as “Bonn’s largest and most important employer”, Deutsche Telekom has “a major social responsibility” that the “Group actively fulfils”.
Sustainability with Measurable Impact
Sustainability is reflected not only in the CityTree’s long service life, but also in its demonstrable environmental impact. According to the current performance report, the biofilter processed around 62.6 million cubic metres of air between April 2022 and July 2026. This corresponds to the volume of air breathed by more than 36,800 people. At the same time, 622 grams of particulate matter (PM2.5) were captured – equivalent to the particulate matter contained in more than 34,000 cigarettes.
In 2026, the average cooling effect on the surrounding air was 3.9 K (°C). During hot summer days in the middle of the heatwave, temperature differences of up to 10.6 K (°C) were recorded – a cooling effect comparable to that of 81 trees.
Photos: GCS
Sustainability – and Rethinking What Already Exists
Every project comes “with a carbon footprint”. Peter Sänger explains: “With more than 110 products installed by now, it is all the more important to ensure that these products make the greatest possible contribution to climate adaptation through their positive environmental impact, thereby turning their carbon balance negative”.
That is precisely what the CityTree stands for: It combines the outstanding natural capabilities of moss with innovative technology to demonstrably improve air quality and provide fresh, healthy air in highly polluted urban spaces.
Bonn as a Symbol of Smart, Healthy Cities
Back in 2020, the General-Anzeiger Bonn described the location as the first project of its kind in Germany to be installed in front of Deutsche Telekom’s headquarters. The video documenting the installation at the time also demonstrated how Green City Solutions and Deutsche Telekom are combining nature and digitalisation to create a more liveable urban microclimate. This was also highlighted by Gabriele Kotulla-Münster, then a member of Deutsche Telekom’s Smart City Unit, and Peter Sänger, CEO and co-founder of Green City Solutions.
With the CityTree’s return in spring 2026, the partnership in Bonn is once again sending a strong signal: for sustainable urban development, for smarte green infrastructure and collaboration with a lasting impact.
Photo: GCS
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