The dispensing system comprises a transportable container and, inside the container, comprises at least a first vessel containing a urea solution, at least a second vessel containing an additive for the urea solution, and at least a first set of fluidic circuits, comprising a first fluidic circuit, connecting the first vessel to a junction, at least a second fluidic circuit, connecting the second vessel to the junction, the second fluidic circuit comprising a valve that can be configured between an open position, in which the first and second fluidic circuits are in fluid communication, and a closed position, and a first dispensing circuit.