Probably only 0.3 percent of the exhaust gases of a diesel engine at full load or at maximum speed are harmful, of which about one third each is NO_X, CO and HC together with particles. The latter still leave a residue of ash after the regeneration described already, even if the engine is operated with particularly low-ash oil.

That adds up, even if there is significantly more space in the particle filter of a truck than in that of a car, where the ashes have to be removed at some point between 100,000 and 200,000 km. In any case, this requires removal and either a new particle filter or a complex burn-out process by specialist companies.

So far as an addendum. First of all, it is about the raw emissions, i.e. the pollutants that can still be avoided in the truck diesel engine itself, i.e. the design of intake ports and combustion chamber, timing, injection in particular and also exhaust gas recirculation and possibly their cooling. Since Euro 4 from 2005, these are no longer sufficient.

The main reasons are that the emission of nitrogen oxides NO_X and carbon dioxide, i.e. the consumption, are regulated at the same time, but exactly exclude each other in the engine. For the lowest possible consumption, a combustion that is by no means too rich, but very hot, is very reasonable. And it is precisely at this operating point that nitrogen oxide emissions would be particularly high.

We skip the norms Euro 4 and 5 and come straight to Euro 6. It's so strict that it doesn't work without an Selectiv Catalytic Reduction catalyst. At most one can save the particle filter, but then the consumption of AdBlue increases. In the picture above you can see a system with a particle filter. After all, the subsequent reduction in NO_X offers the option of paying less attention to nitrogen oxide emissions in the raw emissions and adjust the engine to be more fuel-efficient.

With this picture one have to assume that the exhaust gases of the truck diesel engine flow into the rear container from the right, not without being measured beforehand by a NO_X sensor. They then pass through a relatively shorter oxidation catalytic converter and a longer soot particle filter. Then they get through the pipe at the top into the second container. On the way there, AdBlue is injected at the beginning. The rest of the way through the pipe is used to measure the temperature and the mixture.

In the lower container it first runs through the SCR reduction catalytic converter, which takes up a lot of space, and at the end a so-called blocking catalyst catalytic converter is passed, which prevents toxic ammonia from entering the atmosphere. If a rest has not yet taken part in the chemical reactions, it is converted into nitrogen and water through a reaction with oxygen.

The term 'Oxidationskat' indicates the conversion of nitric oxide into nitrogen dioxide, like any oxidation giving off heat, that then is urgently needed afterwards. In the reduction catalyst, the ammonia from the AdBlue is used to remove the oxygen from the NO_X. The result is nitrogen and water vapor, both normal components of the air.

The entire sensor system, as well as the NO_X sensor at the end, is mainly used to correctly dose the AdBlue amount. The temperature sensor after the oxidation catalyst checks whether the temperature required for the particle filter is reached, e.g. during regeneration. If not, it has to be increased by further post-injection. This is monitored with the help of the temperature sensor after the particle filter. Pressure comparison before and after indicates the filling with soot.

There is even a quality sensor for the AdBlue so that one can't fool by adding water. The level sensor for AdBlue can initiate a rather complicated series of warnings via the engine control unit. That can start already thousands of kilometers before it is empty. Ultimately, however, it is possible that the engine will shut down completely without the chance of restarting.

For heavy trucks, depending on the load and distance traveled, an average consumption of just under 30 liters/100 km is assumed. 5 percent AdBlue is expected, which, according to the manufacturer, would replace the corresponding fuel share via consumption, i.e. a consumption of 1.5 liters/100 km. This means that with a good 0.5 kg proportion of ammonia, 85-160 kWh per t (Wikipedia), i.e. 40-80 Wh per liter of AdBlue, is required for its production.