Cities like Kiel, Heilbronn and Stuttgart try to comply with the nitrogen oxide limit values and bypass driving bans with large air filter systems in the immediate vicinity of their measuring points. The magazine Technology Review goes in its current issue 9/2020 (now at the kiosk or here order) the question of whether this is just measured value cosmetics or actually brings something for people in the vicinity.
“Each column has an effective radius of 10 to 15 meters,” says Jan-Eric Raschke, head of the technology platform Fine dust eater at the filter manufacturer Mann + Hummel, whose Filter cubes installed in Heilbronn and Stuttgart. “The effective radii interlock. We first simulate the air movements on the computer and place the pillars virtually. With this we create a large-scale effect. “
This article is from Issue 9/2020 of the Technology Review. The magazine will be available from August 13, 2020 in stores and directly in the heise shop. Highlights from the magazine:
In fact, the NO2-Measured values have declined “significantly” since the commissioning of 17 filter cubes at the Neckartor in Stuttgart in spring 2019, the responsible Baden-Württemberg Ministry of Transport announced. The filters with four to five micrograms per cubic meter contributed to this. “That is the result of studies in which the filters were switched on and off.” Heilbronn expects a reduction of three to seven micrograms from the 26 filter cubes that it installed in July.
Kiel relies on fewer, but larger, filter systems. This autumn, the city wants to set up six devices from the Schleswig-Holstein manufacturer Purevento. If a filter cube cleans 14,500 cubic meters per hour, the Purevento devices can manage up to 60,000. A prototype set up in 2019 saw a 73 percent reduction in NO at a distance of 1.8 meters2 found, ten meters laterally offset still 28 percent.
But how meaningful are such values? For Jürgen Resch, managing director of Deutsche Umwelthilfe, such air filter systems are simply “not serious” because there are no independent reports. Marcel Langner, head of the department Basic issues of air pollution control at the Federal Environment Agency, confirms: “I am currently not aware of any valid evaluations of how great the effect of air purifiers is – but I do not want to rule out that there are.”
The courts are also skeptical. The Stuttgart Administrative Court, for example, decided at the beginning of July that the DUH can apply for further coercive measures to implement a Euro 5 diesel driving ban (Az. 17 K 3162/20). It was not explicitly about filter systems, but about the entire clean air plan for Stuttgart. “Expert opinions submitted by the state itself forecast that the limit value will not only be exceeded by a significant amount for 2020,” said the judges.
Even the higher administrative court in Schleswig was not convinced by the filter systems at the end of June (Ref. 5 KN 1/19): The effect of the air filter systems assumed by the city of Kiel and the state of Schleswig-Holstein is “not plausible”. According to the expert opinion, “a reduction rate of over 70 percent is achieved immediately behind the respective containers, but this is less than 10 percent in the areas between the containers and drops to zero at one point.”
City and country want to go into revision. “There is an expert opinion on the effectiveness of air filter systems that was part of the offer made by Purevento in response to the city’s tender,” said the city of Kiel. “This expert opinion was presented to the OVG Schleswig at the hearing. But since it contains trade secrets, it cannot simply be made public. ”