Ammonia (NH₃) is gaining attention as a carbon-free fuel at the point of use for large engines - yet NH₃ combustion can generate nitrous oxide (N₂O), a long-lived greenhouse gas with a climate impact nearly 300 times stronger than CO₂.

In the upcoming issue of MTZ (Motorentechnische Zeitschrift), a Swiss research collaboration presents a catalyst route to tackle this challenge - supported and co-authored by Hug Engineering.
 

Why N₂O is the Gatekeeper for NH₃ Engines
 

Ammonia combustion produces no CO₂ at the tailpipe, which is why it is being foreseen for hard-to-electrify applications such as large stationary and marine engines.

However, the exhaust composition of NH₃ engines is complex. Alongside oxygen and water, emissions include:

• NH₃ slip
• NO and NO₂ (NOₓ)
• N₂O

Among these, N₂O is particularly critical due to its very high global warming potential. If ammonia is to become a credible low-carbon fuel pathway, effective control of N₂O emissions is not optional - it is a prerequisite.
 

What the MTZ Publication Reports
 

The MTZ article summarizes results from a research collaboration between leading Swiss research institutions, funded by FVV and the Swiss Federal Office of Energy.

A key conclusion:
Fe-exchanged zeolites stand out as highly suitable catalyst technology to treat N₂O within the multi-pollutant mixture typical of NH₃-engine exhaust.
 

Key Technical Insights

• Strong N₂O conversion at expected exhaust temperatures
  Fe-based zeolite catalysts demonstrate high N₂O conversion already within a practical temperature window for engine aftertreatment systems, achieving conversion rates above 90% under representative conditions.
• Gas matrix sensitivity is a central engineering challenge
  The presence of high steam concentrations significantly influences catalytic performance. Water inhibition effects must be carefully considered in catalyst selection and system design.
• Pollutant interaction matters
  The simultaneous presence of N₂O, NO, NO₂ and NH₃ affects conversion behavior compared to single-component testing. This highlights the importance of evaluating catalysts under realistic exhaust compositions rather than too idealized laboratory conditions.

Together, these findings provide a structured understanding of how catalyst technology must be engineered for ammonia combustion engines - not only in theory, but under real exhaust conditions.
 

Hug Engineering’s Role: Coordinating Research That Can Be Deployed
 

Representing Hug Engineering, Dr. Daniel Peitz led the FVV working group coordinating this research project and is a co-author of the MTZ publication.

For Hug Engineering, this project reflects a core principle:
Fundamental understanding must translate into practical solutions.

By actively coordinating the research framework, we ensured that scientific investigation remained closely aligned with real-world engine requirements and future market applications.
 

From Academic Results to Engine Applications
 

Even while the research project was ongoing, insights were transferred directly into hardware development.

Hug Engineering has already delivered first N₂O catalysts for:

• Single-cylinder ammonia research engines
• A first power plant prototype project 

This rapid transition from laboratory research to applied engine platforms demonstrates how early engagement in fundamental studies accelerates technology readiness for emerging fuel concepts - providing evidence of Hug Engineering’s unique capabilities to support the engine industry’s transition to alternative fuels.
 

What Comes Next
 

The publication also highlights the remaining engineering challenges for N₂O catalysts:

• Long-term hydrothermal and chemical stability
• Robustness under fluctuating exhaust conditions
• System integration into future NH₃ engine and aftertreatment system layouts

These factors will determine how ammonia combustion can evolve from a promising concept to reliable industrial solution.
 

Enabling the Next Generation of Low-emission Engines
 

Ammonia may become part of the future fuel mix - but only if emissions beyond CO₂ are properly addressed.

The research presented in MTZ shows that Fe-exchanged zeolite catalyst technology provides a technically credible pathway for effective N₂O control.

For Hug Engineering, this work represents more than a publication. It reflects our commitment to:

• Driving innovation in exhaust gas aftertreatment beyond today’s technology
• Bridging academic research and industrial implementation
• Enabling new fuel pathways through robust emission control solutions
   

Interested in the full technical publication?

https://link.springer.com/article/10.1007/s38313-025-2156-9 [english]

https://link.springer.com/article/10.1007/s35146-025-2167-8 [german]

The MTZ article is not open access; readers can access it directly via the publisher’s platform. If you would like to receive further information or discuss the findings in more detail, our team will be pleased to support you.