Nitrogen oxides are a focal point of public attention. What would it be like if we could filter it directly out of the atmosphere? Audi is working with a partner company on exactly such a capturing technology. A prototype will soon be entering field trials.
NOx capture can potentially make a revolutionary contribution to cleaning the air in our cities. And it’s unobtrusive, at least visually. The new technology is packaged in a regular freight container marked only by the four rings. Toward the end of the summer, Audi aims to erect it in a busy street in Heilbronn. Alexander Krajete, owner of a startup in Linz dealing with environmental technology, explains the fundamental principle behind NOx capture: “Inside our container are three adsorber units. They’re filled with a special granulate – little dry beads of one to three millimeters in diameter. A fan sucks the ambient air into the adsorber and the NOx is captured by the beads. The air that comes back out of the container has had more than 85 percent of the NOx stripped out of it.”
Road traffic is responsible for a large proportion of NOx emissions. Diesel engines emit more nitrogen oxides than gasoline engines.
85 percent or more is the degree of purification achieved by Audi’s partner, Alexander Krajete.
What is NOx?
Nitrogen is crucial for life on Earth. 78.1 percent of the atmosphere is made up of nitrogen (almost all of the remainder is oxygen). Nitrogen also drives plant growth and is a fundamental element of fertilizer. However, the combustion process causes it to oxidize into vast numbers of gaseous molecules – nitrogen oxides (NOx) made up of nitrogen (N) and oxygen (O) atoms. The most important of them are nitrogen monoxide (NO) and nitrogen dioxide (NO2). Nitrogen oxides have various negative effects on people, the environment and the climate.
Adsorber unit –
Three such cylinders filled with granulate are inside the container..
Die Anlage kann am Tag 80 Gramm NOx aus der Luft binden – so viel, wie rund 10.000 Fahrzeuge NOx ausstoßen.
And how much NOx can the adsorber in the container store? “At its peak, we’re pulling 1,500 cubic meters of air through the system,” says Krajete. “We plan on filtering 30,000 cubic meters of air per day, capturing 80 grams of NOx. This equates to the amount emitted by 10,000 vehicles crossing the intersection every day.”
Nitrogen oxide emissions are quickly diluted in the air. At the point of emission, NOx concentration is still high, but just a light breeze is enough to disperse it and rain washes it away. Therefore, suction into the container is positioned low down and the equipment is located as close to the edge of the road as possible. The project in Heilbronn is an initial pilot test that Audi and Krajete want to use to garner information for the next development phase. But it will bring benefits to local residents and the environment from day one.