NOVELTY - Converting a biomass feedstock into a product hydrocarbon, comprises: (a) subjecting feedstock to fast pyrolysis in substantial absence of oxygen in order to generate fractions of pyrolysis gas and char; (b) converting at least a portion of the pyrolysis gas to product hydrocarbon and carbon dioxide over a catalyst in the presence of hydrogen and steam; (c) generating at least a portion of the hydrogen by reaction between steam and a portion of the pyrolysis gas or the hydrocarbon product; (d) separating carbon dioxide; and (e) separating recycle hydrogen from the hydrocarbon product.    USE - The methods and system are useful for converting a biomass feedstock into a product hydrocarbon (claimed).    ADVANTAGE - The method and system are highly efficient and reliable in producing higher value synthetic fuels, in particular methane.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are:    (1) a cyclic catalytic method for converting the biomass feedstock into a product hydrocarbon, in which catalyst is exposed to a range of temperatures between a higher temperature and a lower temperature, and the catalyst is cyclically subjected to the following steps: (a) an endothermic steam reforming step starting from about the higher temperature and ending at about the lower temperature; (b) an exothermic methanation step starting from about the lower temperature; and (c) an oxidative regeneration step ending at about the higher temperature; and    (2) a system for producing hydrocarbons from biomass, comprising: fast pyrolysis means operating at a process temperature less than 650 degrees C for producing pyrolysis gas and char; independent catalytic conversion means downstream of the fast pyrolysis means operating at a process temperature less than about 650 degrees C for converting the pyrolysis gas to hydrocarbons over a catalyst; and a hydrogen source for adding hydrogen to the independent catalytic conversion means.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of a system for producing hydrocarbons from biomass.    System (1)    Feed preparation section (2)    Feed pressurization section (3)    Pyrolysis reactor (4)    Solids separation section (5)    Catalyst poison removal section (6)    Catalytic hydrogasification reactor (7)    Carbon dioxide removal section (8)    Methane upgrading section (9)    Media heater (10)