An exhaust system for an internal combustion engine, comprising an exhaust gas recirculation (EGR) circuit for connecting an exhaust stream to an intake of the engine, wherein the EGR circuit comprises a heat exchanger and the heat exchanger includes a surface comprising a urea hydrolysis catalyst; and a urea injector for providing urea to the surface of the heat exchanger coated with the urea hydrolysis catalyst, and means for introducing resulting ammonia to the exhaust stream.
