Don’t Kick up Dust

Clean air in the cities would be a great thing. In Stuttgart, researchers, technicians and inventors rigorously tackle fine dust. What is the best way to fight poor air quality?

The Stuttgart-based construction company Züblin is using a modular wall system to investigate whether mosses bind enough fine dust. Photo: Ed. Züblin AG

The Stuttgart-based construction company Züblin is using a modular wall system to investigate whether mosses bind enough fine dust. Photo: Ed. Züblin AG

Swabians can do everything except speak High German. Recently, fine dust management has also become one of the special skills that compatriots from the south like to attribute to themselves. The perfect reference for this is the state capital Stuttgart. Last year, it managed to defuse one of the hotspots in Germany at the Neckartor, which is most heavily polluted by fine dust, to such an extent that the daily average values were within the framework of the legal regulations. So have the Swabians found the ideal way to remove at least fine dust from the thick air? Environmental zones, driving bans, electric cars in urban fleets and eco-tickets for buses and trains are of course also available elsewhere. In Stuttgart, a bundle of measures is being developed that combines classical methods and Swabian inventiveness.

If the weather doesn’t play along, the fine dust alarm comes

The fine dust alarm, for example, goes in this direction. If, during the fine dust period from mid-October to mid-April, the German Weather Service predicts that the atmosphere will have a limited ability to exchange particulate matter on at least two consecutive days, the city triggers a fine dust alarm. This then goes hand in hand with an appeal for the renunciation of the car and a ban on comfort fireplaces. During this period, the typical “Kehrwoche” (sweeping week) at the Neckartor in the region also has a boom. Coordinated by DEKRA, sweepers swarm out on the nights from Sunday to Friday to remove the grit and the comparatively coarse tyre and brake particles by cleaning the road intensively before they can produce fine dust.

Moss plants and high-tech filters bind fine dust from the air

The Swabian metropolis is also considering moss plants as problem solvers. Researchers have discovered that mosses not only bind nitrogen oxides, but also the equally problematic fine dust. Last year, experiments with different types of moss on a 300 square meter moss wall at the Neckartor showed that heat and salt are detrimental to this special property. The Stuttgart-based construction company Züblin is now making a new start with a modular wall system as part of the “MoosTex” research project. The filter manufacturer Mann + Hummel is involved in a rather technological pilot project under the label “Feinstaubfresser” at the Neckartor. The company from Ludwigsburg is currently installing 17 filter columns on a road section about 350 meters long. The columns are 3.60 meters high and consist of cube-shaped components with fine dust particle filters and fans. The systems are designed to extract 80 percent of the fine dust from the ambient air.

At the Neckartor hotspot, sweepers remove the coarse tyre and brake particles before they become fine dust. Photo: DEKRA The filter manufacturer Mann + Hummel is currently installing 17 filter columns at Stuttgart's Neckartor. Photo: Mann + Hummel The mobile variant in the project "Fine Dust Eater" is on the way with several filter systems to reduce fine dust. Photo: Mann + Hummel The filter columns are supposed to draw around 80 percent of the fine dust from the aspirated ambient air. Photo: Mann + Hummel The brake dust filter from Mann + Hummel sits at the brake system and binds the fine dust directly at the source. Photo: Mann + Hummel Deutsche Post is already equipping several StreetScooters with the brake dust filter for a field test. Photo: Mann + Hummel According to laboratory tests, the brake dust particle filter from Mann + Hummel is supposed to collect 80 percent of the brake dust. Photo: Mann + Hummel

With the right filter, the car becomes a fine dust eater

The automotive supplier from Ludwigsburg has also developed a mobile version with various filter systems. Similar to the cubes on the road, the vehicle is designed to extract fine dust from the air. A brake dust particle filter on the brake system is particularly interesting. The system taps off the brake dust at the source, so to speak, preventing it from being released into the environment. If the system proves its worth in Stuttgart, the brake dust filter could have a career in the automotive industry. The Deutsche Post DHL Group is already on the road with a handful of StreetScooters as part of a field test, which, with these filters on board, are advancing to become a almost emission-neutral electric vehicles.

How bizarre can ideas against fine dust actually be?

Ultimately, the Swabian metropolis is concerned with reliably preventing the exceedance of limit values for fine dust at hotspots. In Delhi, the capital of India, on the other hand, the particulate matter problem has long since taken on a completely different dimension. Last year, the World Health Organization declared the megacity to be the world’s most polluted city. Ideas against particulate matter are cheap there – even if at first glance they seem bizarre. They range from particle filters for the nostrils to mobile water cannons on low-loaders to keep the moist particles on the ground. Certain successes in displacing the fine dust particles have probably been achieved with electromagnetic waves such as those used for GPS and weather probes. A big hit is the idea of an Indian entrepreneur who wants to produce liquid ink from soot particles in diesel exhaust gases in order to reduce air pollution. So it is quite possible that in India Swabian inventors with moss plants, filter columns and fine dust alarms will also be seen there at some point.

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