NOVELTY - A hydrogen-generation assembly (46) has a fuel processing system (64), a heating assembly (71), a pressure swing adsorption (PSA) assembly (73), and a combustion fuel stream supply system (140). The PSA assembly can separate a portion of the mixed gas stream into streams forming a product stream and a byproduct stream. The product stream contains pure hydrogen gas and has a reduced concentration of the other gases than the mixed gas stream, and the byproduct stream contains a portion of the other gases.    USE - Hydrogen-generation assembly for producing hydrogen gas used in fuel cell stack. Uses include but are not limited to motor vehicles, recreational vehicles, boats or other sea craft, or residences, commercial offices or buildings, neighborhoods, tools, lights and lighting assemblies, appliances, computers, industrial equipment, signaling and communications equipment, radios, electrically powered components on boats, recreational vehicles or other vehicles, or battery chargers.    ADVANTAGE - The hydrogen-generation assembly can produce pure hydrogen gas.    DETAILED DESCRIPTION - A hydrogen-generation assembly (46) comprises a fuel processing system (64), a heating assembly (71), a PSA assembly (73), and a combustion fuel stream supply system (140). The fuel processing system has a hydrogen-producing region to receive a feed stream and to produce a mixed gas stream containing hydrogen gas and other gases, where the hydrogen gas forms a majority component of the mixed gas stream. The heating assembly can receive and combust stream(s) having a combined combustion fuel value as great as a corresponding, predetermined threshold value and produce a heated exhaust stream to heat and maintain the hydrogen-producing region within a predetermined temperature range for producing the mixed gas stream. The PSA assembly can separate a portion of the mixed gas stream into streams forming a product stream and a byproduct stream. The product stream contains pure hydrogen gas and has a reduced concentration of the other gases than the mixed gas stream, and the byproduct stream contains a portion of the other gases, where the PSA assembly can intermittently discharge a byproduct stream having a predetermined threshold fuel value. The combustion fuel stream supply system can selectively supply the byproduct stream to the heating assembly and also selectively supply, when a byproduct stream having a predetermined threshold fuel value is not discharged from the PSA assembly, an auxiliary fuel stream to the heating assembly, such that the stream(s) supplied to the heating assembly have a combined combustion fuel value as great as the corresponding, predetermined threshold value. An INDEPENDENT CLAIM is included for a method for supplying fuel stream(s) having a combined threshold combustion fuel value to a heating assembly to receive and combust such a combustion stream, and for producing a heated exhaust stream.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a hydrogen-producing assembly in the form of a steam reformer.    Hydrogen-generation assembly (46)    Fuel processing system (64)    Heating assembly (71)    PSA assembly (73)    Combustion fuel stream supply system (140)