NOVELTY - The method comprises: introducing a fuel into a controllable volume; selectively controlling pressure temperature and residence time of residual products and the fuel within the controllable volume; chemically reacting the residual products and the fuel within the controllable volume aided by catalysts (13a, 13b) to produce chemical species; exhausting residual products derived from additional chemical species from the controllable volume; removing the chemical species from the controllable volume via membranes; and controlling volume, pressure, and temperature via actuators.    USE - The method is useful for processing fuel in small-scale, highly scalable reactors for producing hydrogen, which is useful for fuel cell power plants for generation of electricity.    ADVANTAGE - The method is capable of efficiently, economically and rapidly processing fuel in small-scale, highly scalable reactors with reduced size and lightweight in a controlled manner thus generating hydrocarbon fuels with maximum conversion rates and high selectivity and preventing greenhouse effect.    DETAILED DESCRIPTION - The method comprises: introducing a fuel into a controllable volume; selectively controlling pressure, temperature and residence time of residual products and the fuel within the controllable volume; chemically reacting the residual products and the fuel within the controllable volume aided by catalysts (13a, 13b) to produce chemical species; exhausting the residual products derived from additional chemical species from the controllable volume; removing the chemical species from the controllable volume via membranes; controlling volume, pressure, and temperature via actuators; transferring heat to or from the controllable volume; introducing the residual products and the chemical species into a second controllable volume; selectively controlling pressure, temperature and residence time of the residual products and the chemical species within the second controllable volume; chemically reacting the residual products and the chemical species within the second controllable volume aided by the catalysts to produce the additional chemical species; exhausting the residual products derived from the additional chemical species from the second controllable volume; and reintroducing the residual products and the fuel into the controllable volume. The catalysts catalyze fuel-steam-reforming, fuel decomposition and water-gas-shift. The membranes are selectively permeable to hydrogen and carbon dioxide.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a flexible membrane reactor for processing fuel.    Flexible membrane reactors (10)    Fluidically-communicating chambers (11a, 11b)    Catalysts (13a, 13b)    Piston (14)    Hydrogen-selective membrane (17a)    Carbon dioxide-selective membrane. (17b)