Aspects relate to zero-emission propulsion systems and generators using ammonia (NH3) as fuel for engines and power plants. While ammonia has poor flammability, mixing hydrogen with ammonia (NH3) may improve flammability and thus facilitate the ignition of an air/ammonia mixture in engines or power plants. Alternatively, hydrogen (H2) may be supplied in a separate fuel system as a pilot fuel for pilot ignition of an air/ammonia mixture. Hydrogen can also be used in air independent systems along with oxygen (O2) from an oxygen tank. In addition to hydrogen, other bio or fossil fuels can be used as pilot fuel for pilot ignition of an air/ammonia mixture. An advantage of using existing bio or fossil fuels for pilot ignition is that engines or power plants will have a pilot fuel system with sufficient capacity to maintain normal operations if ammonia is not available.