Efficient exhaust gas aftertreatment almost completely eliminates harmful emissions from the combustion of renewable chemical energy carriers.
The combustion process produces waste products in the internal combustion engine, which are then referred to as "exhaust gas". The main component of this exhaust gas is nitrogen (N2), a colorless and odorless gas that makes up more than 70% of the air worldwide. The share of shear emissions in exhaust gas, i.e., gaseous and solid substances that pollute the air, is actually only up to about 1 percent. Nevertheless, the reduction of shear emissions has been a central and important criterion in engine development for decades. In the early 1970s, it became even more important with the introduction of the first uniform exhaust emission regulations for passenger cars in what was then the European Community. Since that time, all applications of internal combustion engines - from road and mobile machinery to stationary and marine applications - have been subject to progressively stricter regulation. Impressive successes have been achieved in terms of environmental and health protection. The limit value for NOx in mobile machinery, for example, fell from 9.2 g/kWh in 1999 to currently only 0.4 g/kWh. Over the same period, the particulate limit value fell even more sharply in percentage terms from 0.54 g/kWh to 0.015 g/kWh, equivalent to a factor of 36. An impressive record!
These successes could only be achieved with extremely efficient exhaust gas aftertreatment, which is constantly being optimized. What once began many years ago as a simple "tailpipe" has since undergone significant technological development and requires a complex combination of in-engine and out-engine measures and technologies in order to comply with the strictest emission regulations: Exhaust gas recirculation, oxidation catalyst, particulate filter and SCR catalysts (which reduce nitrogen oxides by means of urea injection) are now combined to virtually eliminate harmful emissions.
Despite very high technological levels in exhaust gas aftertreatment, the end of development in the avoidance of harmful emissions has still not been fully reached. Renewably generated chemical energy sources can be designed to burn significantly cleaner than their fossil counterparts and, when combined with efficient exhaust gas aftertreatment, enable even lower emission levels. And since regeneratively produced chemical energy sources burn CO2-neutrally, the goal of zero emissions is then almost achieved.