A new Casale technology and plant retrofit solution to decarbonise gas-based (grey) ammonia production by injection of a green hydrogen stream from a co-located water electrolyser which is operated in a load fluctuating mode – as inevitable consequence of being feed by renewable resource derived green kWh. The speech will demonstrate how the Casale solution addresses the challenges of time-variable hydrogen flow stream imposed on the grey plant, resulting in an economical and robust retrofit solution for a specific application case.