A system and a method for treatment of engine exhaust gas (EEG) from an engine (3), which engine exhaust gas (EEG) has a temperature of between T 1 and T 2 , are provided. Provided are also a ship comprising such a system and a use of such a system. The system (1) comprises a SCR reactor (9) for converting NO x contained in a medium (M) containing the engine exhaust gas (EEG) into N 2 and H 2 O. The SCR reactor (9) has an inlet (33) for receiving the medium (M) and an outlet (35) for outputting the NO x reduced medium (M-NO x ). The system (1) is characterized in that it further comprises a mixing unit (7) and a first boiler unit (5). The first boiler unit (5) has a first outlet (19) for outputting boiler exhaust gas (BEG) from the first boiler unit (5), which boiler exhaust gas (BEG) has a temperature of more than T 3 , T3>T 1 . The mixing unit (7) is arranged to mix the engine exhaust gas (EEG) with the boiler exhaust gas (BEG) to produce said medium (M). The mixing unit (7) has a first inlet (27) communicating with the engine (3) for receiving the engine exhaust gas (EEG), a second inlet (29) communicating with the first outlet (19) of the first boiler unit (5) for receiving the boiler exhaust gas (BEG) and an outlet (31) for outputting said medium (M). The outlet (31) of the mixing unit (7) communicates with the inlet (33) of the SCR reactor (9).