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Total loss with moss

The city of Brunswick has spent a lot of money to combat bad air. Now it turns out that the money was not always well invested. Walls with purifying moss did not deliver what they promised.

When the project "Climate Protection with Urban Green" started in spring 2019, Brunswickhad a lot planned: 650 new trees were to be planted and almost 15,000 square metres of roofs and facades of public buildings were to be greened. In addition, there was the idea of installing two moss walls by the company Green City Solutions at traffic junctions that are particularly polluted. According to the manufacturer, these so-called City Trees should bind more fine dust and soot particles than the other two measures combined. This was too good to be true to be dispensed with. Unfortunately, in retrospect it turned out that the effectiveness of the moss walls was not as good as previously stated. The two erectable walls, in which the moss was supposed to filter the pollutants, cost around 110,000 euros.

Now the city has decided to abandon the trial with the moss air filters and not to buy any more moss-covered walls. The reason for this is, on the one hand, that the Institute for Geoecology and Environmental Meteorology at the Technical University of Brunswickcould hardly detect any measurable differences from the previous pollutant levels. Too little for the moss walls to be considered a success. However, the lack of follow-up support from the company Green City Solutions was also criticised: problems with the moss wall were not communicated, sensors failed and the watering of the moss did not take place smoothly.  In comparison, it would also be far cheaper to simply plant natural vegetation.

Because the currently valid limit values for particulate matter and nitrogen oxides are still being complied with in Brunswick, there are currently no plans for an environmental zone in the city. However, the experiment in Brunswick shows that for the other cities in Germany with too high values, there is no other solution than environmental zones and driving bans.