NOVELTY - Storing and delivering ammonia involves providing a container; placing ammonia containing solid material capable of storing ammonia by absorption/desorption in the container; and effecting controlled ammonia release by dosing water into the container in a controlled manner.    USE - For storing and delivering ammonia, useful in selective catalytic reduction of NOx in exhaust gases from combustion processes, in NOx emission reduction from automobiles, trucks, trains, ships or any other motorized machine, power plants generating electricity, stationary and mobile combustion engines fuelled by diesel, petrol, natural gas or any other fossil fuels such as methanol, ethanol, hydrogen, methane, ethane or any other bio or synthetic fuel such as ammonia and hydrogen, coal, oil, as fuel in an ammonia-fuelled fuel cell, in an ammonia decomposition reactor where ammonia is decomposed to nitrogen and hydrogen, and hydrogen is used as fuel in a hydrogen-fuelled fuel cell (claimed).    ADVANTAGE - The method of storage and delivery of ammonia is made safe and versatile by using water to release ammonia, which bound in the solid storage medium. Ammonia is coordinated inside the crystal lattice of a metal ammine salt, but water can replace the position of ammonia due to the same nature of coordination chemistry of electron lone-pairs. Since water is binding slightly stronger to the crystal lattice of the solid, one can extract ammonia without providing any thermal energy of desorption. Thus, the method provides a non-thermal release of ammonia from a solid ammonia-storage material using inexpensive and readily available water.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a system for removing nitric oxide (NOx) from an oxygen-containing exhaust gas of a combustion engine or combustion process, comprising (a) a container with a solid material capable of storing/delivering ammonia by absorption/desorption inside the container, (b) unit for dosing water into the container thus effecting ammonia release, (c) unit for introducing the released gaseous ammonia from the container into an exhaust gas, (d) a catalyst for reducing NOx by reaction with the dosed ammonia, and (e) unit for controlling the amount of ammonia to give an optimal ratio between NOx and ammonia in order to obtain high NOx conversion while minimizing ammonia slip from the gas downsteam from catalyst; (2) a device for providing ammonia for selective catalytic reduction of NOx in an oxygen-containing exhaust gas of a combustion engine or combustion process by using gaseous ammonia and a reduction catalyst, comprising (a), (b), (c), (d) and (e1) unit for controlling the amount of ammonia introduced into the exhaust line, depending on the operating conditions of the engine; and (3) use of dosing of water into a container with a solid ammonia storage material capable of storing ammonia for effecting ammonia release.