Abstract: A system and method for heating main unit containing host salt having ammonia that is used as reductant in an engine exhaust gas after-treatment system. Engine coolant is delivered from internal combustion engine to auxiliary heating device. When necessary, the auxiliary heating device heats the engine coolant to temperatures that will aid in releasing ammonia from the host salt. The auxiliary heating device may employ an electric heating element, a combustion element, or be an exhaust gas heat exchanger, among other heating methods. The heated engine coolant is delivered to a coolant heating manifold, where heat from the heated coolant is transferred to the main unit. The transferred heat may aid in elevating the temperature in/of the main unit to facilitate the release of stored ammonia from the host salt as a gaseous reductant. The gaseous ammonia may then flow from the main unit.