The latest CIMAC Guideline, developed by Working Group 17 “Gas Engines,” explores the influence of ammonia content in biogas on NOx and NH₃ emissions in stationary gas engine applications. Ammonia is commonly present in biogas, with concentrations reaching up to 2% by volume depending on the biomass source and gas cleaning quality.
During combustion, ammonia acts as a strong driver of NOx formation. Studies show that 60–100% of the ammonia in the fuel is converted into NOx, resulting in a measurable increase in exhaust emissions. If ammonia levels exceed manufacturer-specified limits, this can lead to non-compliance with emission regulations and reduced engine oil lifetime.
To ensure stable engine operation and environmental compliance, the guideline emphasizes the importance of maintaining ammonia concentrations below recommended thresholds—typically between 25 and 50 mg/Nm³ for fuels with a lower heating value of 10 kWh/Nm³. Effective gas cleaning and monitoring are essential to control these emissions.
This publication provides valuable insights for engine manufacturers, operators, and developers working with biogas-fueled systems. A follow-up paper will address NOx emissions in engines specifically designed for ammonia as a fuel.