NOVELTY - Hydrogen-producing assembly (12) comprises monolithic body having reforming conduit having feed inlet and reformate outlet, and burner conduit; reforming catalyst to catalyze production of reformate gas stream from the feed stream via endothermic reaction when reforming catalyst is within reforming temperature range; combustion catalyst to catalyze combustion of fuel-air stream via exothermic reaction; and heat transfer structure to distribute heat generated by the exothermic reaction from burner conduit to the monolithic body.    USE - As hydrogen-producing assembly used in fuel cell system (claimed); also useful in hydrogen- and energy-production industries such as fuel cell industries.    ADVANTAGE - The hydrogen-storage device enables product hydrogen streams from the fuel processing systems to be stored for later use.    DETAILED DESCRIPTION - A hydrogen-producing assembly (12) comprises a monolithic body having a length and having a reforming conduit extending longitudinally through the monolithic body, where the reforming conduit defines a feed inlet to receive a feed stream into the reforming conduit and a reformate outlet to deliver a reformate gas stream from the reforming conduit, and a burner conduit extending longitudinally through the monolithic body and adjacent the reforming conduit, where the burner conduit defines a fuel-air inlet configured to receive a fuel-air stream into the burner conduit and an exhaust outlet configured to deliver an exhaust stream from the burner conduit; a reforming catalyst disposed within the reforming conduit and configured to catalyze production of the reformate gas stream from the feed stream via an endothermic reaction when the reforming catalyst is within a reforming temperature range, where the reformate gas stream contains hydrogen gas as a majority component and also contains other gases as minority components; a combustion catalyst disposed within the burner conduit and configured to catalyze combustion of the fuel-air stream via an exothermic reaction; and a heat transfer structure disposed within the burner conduit and configured to distribute heat generated by the exothermic reaction from the burner conduit to the monolithic body; where the monolithic body extends between the burner conduit and the reforming conduit, surrounds the burner conduit and the reforming conduit, and is constructed to conduct heat generated by the exothermic reaction from the burner conduit to the reforming conduit to maintain the reforming catalyst within the reforming temperature range. An INDEPENDENT CLAIM is included for a fuel cell system comprising the hydrogen-producing assembly; and a fuel cell stack configured to receive at least a portion of the reformate gas stream and to produce an electrical output from oxidant and the portion of the reformate gas stream to power an energy-consuming device.    DESCRIPTION OF DRAWING(S) - The figure shows schematic diagram of hydrogen-producing fuel processing system.    Fuel processing system (10)    Hydrogen-producing assembly (12)    Product hydrogen stream (14)    Feed stream (16)    Feedstock delivery system (22)