NOVELTY - A composition comprises either: magnesium powder with a particle size of -50 mesh and a chloride salt; or magnesium powder with a particle size of -50 mesh, aluminum powder with a particle size of -40 mesh and a chloride salt.    USE - For production of hydrogen gas from water; for displacement of hydrogen from water so as to obtain hydrogen gas; and useful in hydrogen gas generation system and hydrogen fuel system which is used to provide hydrogen to device onboard a vehicle (claimed). The hydrogen gas is useful as an energy source.    ADVANTAGE - The composition for the displacement of hydrogen from water is chemically stable under standard temperature and pressure conditions. The method of using the hydrogen fuel system is performed at a reduced cost through the use of a rebate to users for the exchange of at least one salable byproduct that is produced in the hydrogen fuel system during use. The cost associated with transporting and storing the provided composition is low, relative to a composition that is chemically unstable. The cost associated with processing and complexity of a process employing the provided composition is low, relative to a composition requiring extensive pre-treatment. The provided composition poses no serious threat to environmental health or human health. The provided process is suitable for applications requiring portability and mobility; and for stationary applications when and where electricity (i.e. grid infrastructure) is unavailable. The cost associated with disposing byproducts of the provided process is low, relative to a process resulting in formation of environmentally hazardous byproducts. The production of hydrogen in excess of usage requirement is low, relative to a process such that production of hydrogen may not be controlled. The value-added by the byproducts of the provided process is high, relative to a process resulting in formation of salable byproducts of a lesser market value. The uptake and release kinetics are fast, and the weight and environmental toxicity of the hydrogen fuel system are low, relative to a physico-chemical hydrogen fuel storage system. The pressure and volume of the system is low, relative to a compressed gas hydrogen fuel storage system.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a hydrogen gas generation system, comprising either: the magnesium powder, chloride salt and water; or the magnesium powder, aluminum powder, chloride salt and water;    (2) displacement of hydrogen from water so as to obtain hydrogen gas, involving: adding the composition to water to form the hydrogen gas generation system; and collecting hydrogen gas from the hydrogen gas generation system; and    (3) a hydrogen fuel system comprising: a refillable water tank (2); a refillable reaction vessel (1); and a hydrogen gas accumulation vessel (3), where a feedstock composition comprises finely divided magnesium and chloride salt or finely divided magnesium, finely divided aluminum and chloride salt, is contacted with water from the refillable water tank in the refillable reaction vessel so as to produce hydrogen gas, and the hydrogen gas is provided to a device (8) that uses the hydrogen gas to create energy and any excess hydrogen gas is supplied to the hydrogen gas accumulation vessel where the excess hydrogen gas is stored until needed.    DESCRIPTION OF DRAWING(S) - The figure shows a hydrogen fuel system.    Refillable reaction vessel (1)    Refillable water tank (2)    Hydrogen gas accumulation vessel (3)    Device that uses hydrogen gas to create energy (8)