Maritime Designer Award Grant: ammonia combustion results

In 2020, C-Job’s Niels de Vries won the Maritime Designer Award for his research into ammonia (NH3) as a green alternative fuel. Part of the award was a grant to C-Job for further research into ammonia propulsion. Two years on, that program has been successfully completed, demonstrating that using diesel / ammonia mixes in internal combustion engines can reduce harmful emissions compared to 100% diesel fuel. These results will contribute to the next stage of the industry-wide research into this vital technology.



The research C-Job outsourced to Progression-Industry, funded by Stichting Timmerprijs, looked at the impact on performance of initiating ammonia diesel combustion in a modified diesel engine. The diesel (pilot) is injected directly into the cylinder and ignites based on compression ignition. This combustion of the diesel than ignites the ammonia already present in the cylinder. In the test engine the ammonia is injected via the air intake port. This test engine is connected to an electric generator which provided the load. Four series of tests were run: first a baseline 100% diesel test, followed by a second test with LPG added in incremental amounts, and then two with ammonia (low and high pilot). A variety of sensors measured the emissions from each test run, along with the engine’s performance in terms of power output and torque.

Test results

  • Engine efficiency was similar across the four series of engine tests.
  • NOX levels rise then fall – When low amounts of ammonia were added to the diesel the resulting NOX emissions were relatively high compared to 100% diesel. This was possibly caused by the nitrogen that forms part of ammonia. However, as the proportion of ammonia in the fuel rose, the NOX emissions started to decrease. This could be due to the lower temperature at which ammonia burns.
  • CO2 and particulate matter emissions both fall – When compared to 100% diesel, the PM and CO2 emissions fall as ammonia does not contain carbon.
  • NH3 – A certain amount of the ammonia is not combusted and is expelled through the exhaust. As the engine load increases so do the ammonia emissions. This is caused by the lower pilot fuel fraction at higher engine loads.

Based on this research, with its main conclusions about ammonia diesel combustion in general, it is clear that additional research is required to fully determine what these results mean for the future of marine engines. These results provide preliminary indications and more detailed knowledge about ammonia diesel combustion and can be the basis for the further development of marine engines. Therefore, we offer the following recommendations regarding further research:

  • N2O – We were unable to test for nitrous oxide emissions at the time. This should be a priority in the next round of research.
  • Alternative injection methods – Direct liquid ammonia injection rather than the port fuel injection that was used in our research would improve combustion at high load levels. This requires evaluation.
  • In addition, other studies have shown that larger, turbo-charged engines can achieve much higher ammonia fractions due to increased oxygen concentration promoting combustion. This should be investigated further.

The research project is just one example of C-Job’s active involvement in the development of green propulsion in general and ammonia in particular. Another is our membership of the EU-funded ENGIMMONIA consortium, where we have a remit to assist on system and technology integration and managing design-related modifications to various vessels. Other collaborations are also in the pipeline.

Despite the limitations of the available budget and the test setup, the results are another step in the development of ammonia as a marine fuel, showing the preliminary state of its potential and the challenges that lie ahead, says Niels de Vries, Lead Naval Architect at C-Job Naval Architects . As per our recommendations the next step would be to further research ammonia diesel combustion in a turbo charged engine, with direct liquid ammonia injection, preferably at a larger scale. This will lead to more representative results for marine engines.”

As acknowledgement, C-Job would like to thank Stichting Timmersprijs for providing the funds and Progression-Industry for executing this research with the limited resources.

A link to a summary of the research report can be found here.