The current Auxiliary Power Units (APUs) in transport aviation run on kerosene (= an upgraded diesel fuel) is also made suitable for operation under varying atmospheric conditions – air pressure and temperature and high-reliability fuses) from the tanks of the aircraft and consumes an average of 150 liters per hour, with high noxious emissions as a result. LNG, the cleanest fossil fuel in the transport sector that is currently available in large quantities, has not been developed and commercially available for APUs in transport aircrafts. During this project, an existing APU will be retrofit and will be connected to a separate LNG tank that will work on both kerosene and LNG, in order to reduce noxious emissions during the turnaround phase of every transport aircraft. Besides that, Honeywell and Safran have developed an electric taxiing system (link) which enables aircraft to avoid using their main engines during taxiing and instead taxi autonomously under their own electrical power, using the APU generator. If this system is installed on the current aircraft, APUs will play a more important role in the future and a hybrid APU can even reduce more fuel consumption and noxious emissions.