The regulation for emission levels from combined heat and power plants might vary depending on the country, legislation in the particular country and regulations of a local council.
In Germany, as example, the so-called TA Luft regulates emission levels for a particular segment.
Oxidation catalysts are used to reduce the level of CO and formaldehyde emissions (HCHO). The catalytic performance depends on different parameters, like gas temperature, pressure, impurity level. Some gases, like landfill gas, contain a variety of catalysts poisons, like H2S or siloxanes.
To make sure that the catalyst will achieve a certain life time and performance it is important to purify the gas up-stream of the engine, e.g.by activated carbon.