NOVELTY - A system for storing ammonia in and releasing ammonia from a storage material, comprises a container (1) for housing the ammonia-containing storage material; a heating source (2) to supply heat for desorption of ammonia from solid storage medium; a controller (12) to control the heating source; and a controllable dosing valve arranged to dose released ammonia according to the ammonia demand. The controller comprises a feed-forward control arranged to control the heat supplied by the heating source, based on the ammonia demand.    USE - For storing ammonia in and releasing ammonia from a storage material; for removing nitrogen oxides (NOx) from an oxygen-containing exhaust gas of a combustion engine fulled by diesel, petrol, natural gas, coal, hydrogen or other fossil or synthetic fuel; for reduction of nitrogen oxides produced by automobile, truck, train, ship or other motorized machine and vehicle; for using desorbed ammonia as a fuel for power generating unit and fuel cell (claimed); and for comparing ammonia demand and the measured mass flow, and for controlling the controllable dosing valve such that the measured mass flow matches the ammonia demand. METALLURGY - The heat-conducting elements are made of porous or dense aluminum, titanium, stainless steal or similar ammonia resistant metals or alloys.    ADVANTAGE - The system delivers ammonia directly in the form of a gas, both for the simplicity of the flow control system and for an efficient mixing of reducing agent, ammonia, with the exhaust gas. The direct use of ammonia also eliminates potential difficulties related to blocking of the dosing system which are caused by precipitation or impurities e.g. in a liquid-based urea system. In system, an aqueous urea solution cannot be dosed at a low engine load since the temperature of the exhaust line would be too low for complete conversion of urea to ammonia (and carbon dioxide).    DETAILED DESCRIPTION - A system for storing ammonia in and releasing ammonia from a storage material capable of binding and releasing ammonia reversibly by adsorption or absorption for a process with a gradual ammonia demand that can vary over the time, comprises a container (1) capable of housing the ammonia-containing storage material; a heating source (2) arranged to supply heat for the desorption of ammonia from the solid storage medium; and a controller (12) arranged to control the heating source to release ammonia, where the heating source being arranged inside the container and surrounded by ammonia storage material; a controllable dosing valve arranged to dose released ammonia according to the ammonia demand. The controller comprises a feed-forward control arranged to control the heat supplied by the heating source, based on the ammonia demand. The desorption of ammonia from the storage material is endothermic, and the feed-forward control is arranged to control the heat supplied by the heating source such that it compensates the energy required for the endothermic desorption of the demanded ammonia from the storage material. The system further comprises nitrogen oxides (NOx) sensor. An INDEPENDENT CLAIM is included for releasing ammonia stored by storage material housed in a container and capable of binding and releasing ammonia reversibly by adsorption or absorption for a process with a gradual ammonia demand that can vary over the time, involving determining how much heat is to be supplied to the ammonia storage material for the desorption of ammonia by means of a control comprising a feed-forward control, based on the ammonia demand; supplying the heat by a heating source arranged inside the container and surrounded by the ammonia storage material; dosing released ammonia by means of controllable a dosing valve according to the ammonia demand. The heat-conducting elements are constructed of a porous metal structure that passes released ammonia from the surface of the storage material being in contact to fin (3).    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the ammonia storage and release system.    Container (1)    Heating source (2)    Fins (3)    Pressure sensor (10)    Controller. (12)