A steady supply of urban fresh air plays a very important role in public health. According to the World Health Organisation, air pollution is now the world’s largest single environmental health risk, causing millions of death per year.

Globally, city administrators continue to exploit ways to make the air in cities safer and GreenTech entrepreneurs are actively pushing the boundaries of available solutions in this space.

Berlin-based Green City Solutions is promoting its City Tree technology designed to act as super-trees, reported having the environmental benefit of up to 275 actual trees. This is an interesting addition to the mix of urban air purifying technologies.

City Tree – A perfect combination of plants and IoT (Photo: www.greencitysolution.de)
Planting trees and improving the greenery has been one of the most common ways applied to improve air quality in urban areas. However, the economics of planting new trees and maintaining them is also an issue for city administrators. This is the selling point for mobile installations like the CityTree. It has been popping up in cities around the world, including Oslo, Paris, Hong Kong, etc.

Technology Highlights

  • The City Tree is actually a moss culture. The huge surfaces of moss installed in these each tree can remove dust, nitrogen dioxide, ozone gases, etc from the air. “Moss cultures have a much larger leaf surface area than any other plant. That means we can capture more pollutants,” Zhengliang Wu, co-founder of Green City Solutions, told CNN.  Each installation is about 3 meters (9.84 ft) wide, stands at almost 4 meters (13.12 ft) tall and was planted 2.19 meters (7.19 ft) deep.
  • The CityTree includes sensors that measure the local air quality. These WiFi enabled sensors to monitor the health of the moss, measure soil humidity, temperature and water quality. According to their website, it also has pollution sensors inside the installation, which help monitor the local air quality, telling how efficient the tree is.


Viable indoor installation (Photo Credit: Green City Solutions)


Each CityTree is reported to be able to absorb around 250 grams of particulate matter a day and contributes to the capture of greenhouse gases by removing 240 metric tons of CO2 a year. Furthermore, the tree can operate with a high degree of autonomy and requires very little maintenance – solar panels provide electricity, while rainwater is collected into a reservoir and then pumped into the soil. A display is included for information or advertising.
The challenge for having fresh air in cities is that you need to clean massive volumes of air. Some experts believe this is best handled by stopping the pollution from forming in the first place – laying more emphasis on technologies that reduce air pollution at the source. In any case, having effective air purifying systems ready to be deployed citywide is a welcome development and is a technology that should be improved.


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