Mads Carsten Jespersen and a team of researchers from Technical University of Denmark (DTU) presented research into widening the operating limits of a spark-ignited engine operating on pure ammonia and confirmed that combustion of 100% ammonia, pre-mixed with air but without an ignition improver is feasible.

While most previous studies have involved the addition of 5% hydrogen as an ignition improver for ammonia combustion, DTU researchers have shown that the safety and complexity challenges associated with this use of hydrogen can be avoided by optimising the spark ignition system.