Exhaust emissions: Ministry of Transport finds software updates more effective than retrofitting

The Federal Ministry of Transport of Andreas Scheuer (CSU) continues to refuse a technical retrofitting of older diesel models. In a calculation submitted to the German Press Agency, the ministry presents figures to support this attitude.
            Due to updates of installed software, according to the ministry's statement, the emission of hazardous nitrogen oxides could be reduced by 6.3 million vehicles. A technical conversion, however, is only possible with about two million cars.
            The preparatory work for a hardware retrofit of the exhaust gas purification directly on the engine would take at least two years, which is why, in the year 2020, comprehensive retrofitting could be started.
However, according to the Ministry of Transportation, nitrogen oxide emissions are reduced by 65 percent for a technical upgrade, and only 30 percent for a software update. With around 6.3 million cars with an average NOx emission of 750 milligrams per kilometer, an update – summed up on the performance of all retrofitted vehicles – could lead to a reduction in nitrogen oxide emissions of 1,417 tonnes per kilometer. In addition, 3.2 million diesel have already been converted, and this process could be completed in 2019.

particulate matter

What is air pollution?

Dirty it is outside by pollutants from various sources: industry, road transport, agriculture, energy production and nature itself. The cleaner the air, the less people suffer from strokes, cardiovascular diseases, lung cancer or respiratory diseases such as asthma. People also live longer, if they can breathe fresh air. The World Health Organization (WHO) estimates that in 2012 alone, three million people worldwide would have lived longer if air pollution had been lower.

particulate matter

Particulate matter includes all airborne particles that consist mainly of sulphate, nitrate, ammonia, sodium chloride, carbon, mineral dust and water. These can be soot particles, tire wear, plastic particles, fertilizer and waste residues. The particles float solid or liquid in the air and are dangerous if they have a diameter of ten microns or less. The smaller the suspended particles, the easier they can get deep into the lungs, even into the bloodstream. Particulate matter statistically increases the risk of cancer, especially in the lungs. How exactly the particles trigger ulcers, but so far not clarified.

Nitrogen oxides

Nitrogen oxides, abbreviated as NOx, are the number one pollutant in most cities. The toxic gas mixtures are mainly produced when oil, gas, wood or coal are burned, for example for heating or to generate electricity. Old diesel and combustion engines emit relatively high levels of nitrogen dioxide (NO2). Ship engines also throw this special nitric oxide into the air. NO2 can cause acute respiratory infections in concentrations greater than 200 micrograms per cubic meter of air. In the long term, this can trigger asthma and bronchitis. In Germany, the limit of 40 micrograms per cubic meter of air was exceeded in 2016 at more than every other traffic-related measuring station in the annual average.

sulfur dioxide

Sulfur dioxide (SO2) is a gas that smells sharp. It occurs when, for example, fossil fuels such as coal or oil go up in flames to generate electricity, heat homes or drive vehicles. Even if ores are extracted and melted, toxic sulfur compounds are formed. SO2 can irritate the respiratory system, lungs and eyes. It makes asthma and bronchitis worse. Breathing difficulties already occur within ten minutes if the SO2 concentration is 500 micrograms per cubic meter of air or more. Anyone who is exposed to an average daily load of 20 micrograms of SO2 per cubic meter of air for a prolonged period of time also has to reckon with respiratory problems. If sulfur dioxide reacts with water in large quantities, it also forms sulfuric acid, the main constituent of acid rain. This damages mainly plants and forests.


Ozone (O3) as a part of dirty air on the ground is something other than the ozone layer in the upper atmosphere of the earth. Smog in big cities like Beijing is mainly ozone. It arises when sunlight reacts with pollutants such as nitrogen oxides or with organic particles from solvents and industrial processes. Therefore, smog occurs mostly in weather conditions with lots of sun. It irritates the lungs and can cause asthma and other respiratory diseases. An increased risk of cardiovascular disease was found by researchers from a long-term ozone concentration of ten micrograms per cubic meter of air. In comparison, in Beijing, concentration in the past has already reached values ​​of around 300 micrograms per cubic meter of air for several consecutive days.


Volatile organic compounds (VOCs for volatile organic compounds) are gaseous carbon compounds such as alcohols, terpenes or aldehydes. They arise in a natural way, for example by plant metabolism or decay processes. However, they mainly form when exhaust fumes are burned or evaporate from chemical products based on petroleum. Soaps, perfumes, paints, varnishes, cleaning agents, adhesives and pesticides are often underestimated pollutant sources that cause bad air, especially indoors. VOCs are very responsive and can float through the air in many shapes. For example, they can react with other gases to produce ozone or minute particulate matter. Their consequences for the health: In high concentration they irritate eyes and mucous membranes, make tired or cause headaches and dizziness.
A technical conversion to minimize pollutant emissions would only be eligible for one-third of all Euro-5 diesel engines: due to the space available, not all vehicles allowed the hardware to be retrofitted. The two million cars that could be rebuilt would result in a reduction in nitrogen oxides of 975 tonnes per kilometer of all retrofitted vehicles, with a saving of 65 percent. And "only if everyone participates in a costly hardware retrofit", it says in the calculation of the Ministry.
Following this argument, the hardware retrofit has a 32 percent lower efficiency than a software upgrade.