United for the Future of Water and Resilient Sponge Cities
Water is our most precious resource – and it stands at the heart of urban transformation. At the 3rd cross-state Water Congress Berlin-Brandenburg-Saxony on May 12 and 13, 2025, around 250 experts from politics, business, and science discussed innovative solutions for a secure, sustainable, and resilient water supply. Green City Solutions participated with CEO Peter Sänger as a driving force for bio-digital innovations and the sponge city concept.
Photos: Konstantin Gastmann
The Challenges: Climate Change, Structural Transformation, Water Scarcity
The pressure to act is high: climate change, population growth, and the structural transformation resulting from the coal phase-out are intensifying conflicts over water use. The next ten years will be crucial for developing viable strategies for water supply in Berlin, Brandenburg, and Saxony. As the Berlin Association of Merchants and Industrialists (Verein Berliner Kaufleute und Industrieller, VBKI) summarizes: “Water is becoming a scarce resource. Climate change and structural transformation are intensifying usage conflicts – prioritization and viable strategies are urgently needed.”
“Berlin and Brandenburg are among the driest regions in Germany. How can we ensure water supply in our region?” asked rbb24. The Water Congress provided an ideal platform to work together on solutions for a resilient, sustainable, and livable city of the future.
Sponge City: Moss as Green Sponges for the City of Tomorrow
A central topic of the congress was the sponge city principle – a future model for sustainable urban development and climate adaptation. Sponge city means: “Rainwater should not simply flow into waterways via the sewage system, but should be collected and stored for use where it is needed.” As a spokesperson for the Association of Municipal Enterprises (Verbands Kommunaler Unternehmen, VKU) told rbb: “Stored rainwater can be used for irrigation, saving valuable drinking water.”
Green City Solutions presented bio-digital innovations such as WallBreeze, CityTree, and CityBreeze, which harness the natural abilities of mosses as “green sponges”. These store and evaporate water, purify the air and sustainably improve the urban climate. In this way, these natural filters make an active contribution to climate adaptation, enhancing urban quality of life and protecting valuable resources.
Our CEO Peter Sänger spoke in his presentation at the Water Congress 2025 about the most important resource – besides air – and how the sponge city concept can be put into practice.

Photo: Konstantin Gastmann
Collaboration and Innovation: Solutions for the “Water Future of Our Regions”
The Water Congress impressively demonstrated the importance of cross-state cooperation and innovative approaches. “‘We must learn to think and act together,’ said VBKI Managing Director Ute Weiland as she opened the discussion.” Effective collaboration can quickly deliver impactful solutions. “Water policy can only be successful if it is considered across departments and state borders.”
IHK Berlin emphasized: “The positive aspect: the commitment to finding solutions across borders is greater than ever” – in other words: water is on everyone’s lips.
Ramona Giese, Senior Consultant at Drees & Sommer, wrote in her LinkedIn summary “Absorb it and store it”: “There are many levers, but also already proven approaches such as rainwater storage, evaporation through greening, and green retention roofs that are putting us on the right track.”
Excursions, Exchange and Innovative Pitches
“Coordination instead of competition was one of the most important topics of the day.” The program included excursions to sponge city projects with the Berlin Rainwater Agency, a networking evening on the Spree, and four pitches from innovative companies such as Green City Solutions, LuxChemtech and KWB Energiesysteme.
A heartfelt thank you to all participants, contributors, and organizers! We look forward to further exchange and inspiring collaborations.
Photos: Konstantin Gastmann & Stephan Gruhlke
For example, Stephan Gruhlke, mayoral candidate of Eichwalde, was inspired after Peter Sänger’s presentation:
This visit has since taken place, as he was “curious about innovative ideas” and was “informed on site by the experts about a great concept.” His conclusion: “Here, solutions are being developed that use highly sophisticated moss mat technology for natural air purification in both indoor and outdoor areas.”
Regional, Connected, and Future-Oriented: The Sponge City as a Key to Resilient Cities
“In Germany, the first drought reports of the season are already accumulating. The perfect timing” for the Water Congress 2025. The event made it clear: the sponge city is a key to climate-resilient, livable, and sustainable cities of the future. Moss-based innovations such as WallBreeze, CityTree, and CityBreeze make an active contribution to climate adaptation, air purification, and resource protection.
The coming years will be decisive – now is the time to work together on solutions for a resilient water future.

Photo: Konstantin Gastmann