Even if several studies performed during the mid-60’s investigated the possibility to consider ammonia as a fuel for internal combustion engines, mainly by means of CFR experiments or OD modeling, ammonia-based combustion engine fueling methods are not ready to be marketed not only because of supply and safety issues but also because of its combustion characteristics compared to conventional fuels.

To supply ammonia either partially in standard internal combustion engines to limit carbon footprint or in dedicated engines to reach zero carbon footprint, the technological challenges (dual fuel or unique fuel, SI or CI engines …) could be different as a function of the final use.

This talk will present a summary of the knowledge on ammonia as a fuel for an internal combustion engine. Some indications about the performance of ammonia fuel only in current internal combustion engines, pollutant emissions, and operating limits will be presented and discussed, highlighted by newly updated results in order to underline the technological and scientific barriers that remain to be overcome.