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Interview Environment

Combining economy and ecology to battle urban air pollution


Words by Suzanna Knight

Photos by Robert Rieger

With reports that 92% of the world’s population currently lives in places where air quality levels exceed their pollution limits (World Health Organisation), it’s time to take action. For Berlin-based Green City Solutions, it was the trigger to develop CityTree, a 4-metre-high billboard covered in moss that’s able to filter the pollution of up to 417 cars annually whilst cooling down the surrounding air (and providing Wi-Fi!) We met up with founder Zhengliang Wu to learn more about this multi-functional super tree.

Tell us about the CityTree. How was it developed?

Dénes Honus, Peter Sänger, Victor Splittgerber and I cofounded Green City Solutions in 2014 as a CleanTeach startup, looking to develop sustainable ways to improve the quality of city living. We come from fairly varied backgrounds including architecture, biology, IT and design but our shared vision regarding the current social and environmental challenges we face is what brought us together. We wanted to create a green air filter, something that would help battle the pressing issue of urban air pollution in a sustainable and practical way. We went through various prototypes, all to test and use the natural conditions in cities and street canyons. The end result was CityTree, a free-standing, vertical billboard covered in a specific moss culture with vascular plants that absorb and ‘eat’ toxins like nitrogen dioxide in the air. It has the same effect as 275 trees, but requires 99% less space and only 5% of the costs, and just a few hours of maintenance every year.

Why do you think the CityTree needs its current multifunctional purpose?

We involved potential customers from day one, and their feedback and critique made us realise we had to create something that combined ecology and economy. We knew from the very beginning that we could not survive as a company with a product that only serves the ecological needs of a city, because the cities with the worst air pollution usually have the lowest budgets to deal with the issue efficiently. Not just cities in Asia or America- even European cities have limited budgets that they have to spend wisely in order to meet the targets set by the EU. By making the CityTree multifunctional and installing it as a billboard, we don’t have to depend on city governments for revenue, and can give the CityTrees away for free. The multifunctional purpose does not only help citizens by letting them use it as a bench, charging station, billboard or even WI-FI Hotspot, we can also accelerate their installation where and when they are needed because there really is no time to waste.

What other challenges did you face when producing the product and getting it installed in cities?

There were challenges regarding the footprint of the entire product, because we wanted to make the CityTree as sustainable as we could by using as many recyclable materials as possible. It’s hard to find reliable producers who can fulfil that criteria and still deliver on time with a consistent high level of quality. As mentioned before, the nature of governmental structure usually makes the procurement phase much longer than anticipated. It’s understandable- they have to guarantee the safety of their citizens and the sustainability of a product, and find appropriate use for public funds. But we share those goals, we all want a better environment for people in cities, so it’s also up to us to work together to guarantee those goals and solve any problems.

We wanted to create a green air filter, something that would help battle the pressing issue of urban air pollution in a sustainable and practical way.

What do you think could or needs to change to make green initiatives like this easier to implement in cities?

The majority of the cities and municipalities we have been in contact with have reacted very positively and are now looking for a way to implement the CityTree. But with a limited budget and the need for public acceptance of green initiatives they also have to prove that these projects do have a sustainable impact, and can deliver on their promises. We should be doing more to raise awareness of the deplorable state of air quality in our cities. If more people become aware of the existing problems and the impact that projects like this can have, and if more people voiced their desire for cities to spend money on similar projects, the easier it would get to accelerate the process.

The CityTree was your first solution. What other solutions would you like to develop in the future?

We’d like to work on something that a lot of people have asked us, and that is to create a solution to improve indoor air quality. There are many people who spend most of their days inside, like children or elderly citizens, and are therefore more threatened by indoor air pollution than outdoor pollution. We’d like to create a modular system to make the whole solution scalable and applicable to any environment.