Method and arrangement for treating exhaust gas mixture

A method (200) for treating an exhaust gas mixture comprising a fuel vapor of a fuel and an inert gas, the exhaust gas mixture originating from a fuel system (120), the method (200) comprising: directing (S202) the exhaust gas mixture from the fuel system (120) to a condenser (131), the condenser (131) condensing at least a majority of the fuel vapor into a liquid fuel, such that the exhaust gas mixture comprises a liquid fuel and an inert gas; separating (S204) liquid fuel and inert gas from the exhaust gas mixture of the condenser (131) in a vapor-liquid separator (133); and selectively directing (S206) the liquid fuel from the vapor-liquid separator (133) to the boiler system (110) or storing (S208) the liquid fuel in the vapor-liquid separator (133) and/or in a separate storage tank (135) when the boiler system (110) is in a hot state and ready to receive and burn the liquid fuel of the exhaust gas mixture, until the boiler system (110) is in a hot state and ready to receive and combust the liquid fuel of