SCR Catalyst


In Germany, the 44th BImSchV of 20 June 2019 sets stricter emission limits for CHP plants with a medium-sized rated thermal input of 1 to 50 megawatts. This roughly corresponds to a plant size of 400 kW upwards. 

What does this mean for CHP operators? The 44th BImschV affects new and existing plants that are operated on the basis of natural, bio or special gases: CHP operators must reduce the limit values for a number of exhaust emissions, first and foremost for nitrogen oxides (NOx), carbon monoxide (CO), formaldehyde (HCHO), hydrocarbons (HC), ammonia and dust. With an SCR catalytic converter, however, the new limits can be met without any problems. 

Secondly, plant operators must measure, document and prove the emissions of their plant: The verification and documentation obligation already applies today. 

With flexibly adaptable SCR catalytic converters and NOx measurement boxes, we at Bücker + Essing get the best out of every plant. During the planning phase, we take a close look at the parameters of each plant, e.g.: 

  • What are the spatial conditions? 
  • Is there waste heat that we can use for winter protection of the tank containers? 
  • How can interfaces be integrated? 



Schmelzerstraße 25
47877 Willich
T +49 2154 488-0

Randolf Oprée
T +49 2154 488-268
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On the safe side with SCR cat

The Bücker + Essing SCR catalytic converter technology reduces the NOX emissions of a CHP unit by up to 90 percent and thus easily complies with the new limit values of 100 mg/Nm³ for natural gas and biogas plants: By injecting urea ("AdBlue"), nitrogen oxides are converted into natural nitrogen and water. The amount of urea is automatically metered and adjusted to the nitrogen oxide content and engine parameters such as operating temperature and load condition. In the case of new systems, we also integrate the oxi-cat into the catalytic converter housing, which enables you to comply with the new formaldehyde limits, among other things.

Your advantages: 

  • For units up to 600 kW, our SCR catalytic converter does not require compressed air. This makes our technology particularly space-saving, maintenance-friendly and cost-effective. 
  • Your spatial conditions are used in the best possible way: We can install the components of the catalytic converter technology, such as the catalytic converter housing, the urea tank, pipelines and the control cabinet individually in the existing exhaust gas section or place them outside the CHP container as an external container solution.
  • We offer various tank models for the AdBlue solution for indoor and outdoor installation. Of course, we will be happy to check whether waste heat from your system can be used to heat the tank.
  • We optimally adjust the engine and exhaust gas aftertreatment to each other.

Another plus: SCR technology often increases the efficiency of systems, especially natural gas CHP units. This means that the investment costs for the SCR catalytic converter and additional expenses for AdBlue can be partly compensated for by reduced natural gas consumption. We will be happy to advise you on the effects on your plant!   


What does this mean in concrete terms for CHP operators? The following applies to new plants that have been or will be commissioned after 20.12.2018:

  • Biogas-fuelled combustion engines must reduce NOx limits from 500 to 100 mg/Nm³ from 2023. 
  • Natural gas-fuelled combustion engines must comply with the reduced NOx limit values of 100 mg/Nm³ from 2025.  

Existing plants that are operated on the basis of natural gas or biogas and were commissioned before 20 December 2018 must reduce the NOx limit values to 100 mg/Nm³ from 2029 and be retrofitted with an SCR catalytic converter accordingly.

For new plants, we already take catalytic converter technology into account as standard in every project planning, because it requires space in the exhaust gas section.

Anyone planning a new CHP now has two options:

Pre-install SCR cat

With every new PRO2 CHP unit, we already plan the SCR catalytic converter and equip it with a pre-installation. All elements that require space or have to be installed in inaccessible places, such as the catalytic converter housing with oxi-cat, control cabinet, piping and heat extraction for heating an external tank, are already installed by us when we deliver your new CHP unit. Further hardware and software can easily be retrofitted to commission the catalytic converter.

Install complete SCR cat

If you want to actively promote climate protection in your plant, you can have your new PRO2 CHP equipped with complete SCR catalytic converter technology now. You will no longer have to worry about retrofitting later and will operate your CHP unit in compliance with the future limit values right from the start. Another plus: You benefit from a higher efficiency of the plant right from the start.

Retrofitting existing plants

Existing plants that were commissioned before 20.12.2018 must comply with the low limit values from 2029. We place the catalytic converter technology either in the CHP unit or as a container solution outside the unit. Retrofitting is also possible in confined spaces! We will be happy to advise you on project planning and implementation, please contact us!