NOVELTY - Producing hydrocarbon from biomass involves: performing fast pyrolysis on biomass to produce pygas and char using a maximum processing temperature of 650 degrees C; and providing the pygas to an independent reactor without the addition of an oxidizing agent for catalytically converting the pygas to hydrocarbons using a maximum processing temperature of 650 degrees C, where both performing fast pyrolysis and catalytically converting the pygas to hydrocarbon minimizes tar production to (less than 1%) of biomass processed relative to amount of tar produced from that biomass.    USE - For producing hydrocarbon from biomass; and for hydrogenating a material in a conversion reactor (claimed). The hydrocarbons are useful for injection into gas pipeline or liquefaction facility for contribution as widely distributed good e.g. as fuel for supplying to natural gas internal combustion engine or turbine to generate power, as supply for compressed or liquefied natural gas station for transportation fuel, or as fuel for natural gas boilers and burners to produce renewable heat energy; as feedstock for chemical processing for renewable product manufacturing; and for feeding the hydrocarbon product to a high temperature fuel cell, such as solid oxide fuel cell for production of electricity.    ADVANTAGE - The method provides conversion of biomass to useful gaseous and liquid hydrocarbons, while avoiding problems caused by the formation of undesirable tars, such as the method minimizes tar production to (less than 1%) of biomass processed relative to amount of tar produced from that biomass. It is found that in the process, the formed char is catalytic to the dehydrogenation and other reactions of pygas, creates additional secondary char and secondary condensable products such as heavy aromatic compounds, where secondary tar formation increases with process severity including both process temperature and residence time. Hence process severity is reduced by reducing contact time between the formed primary char and generated primary pygas, such as in the fast pyrolysis the char contact time with the pygas is less than 5 seconds. The reducing of the contact time between primary chars and vapors is performed by use of a sweep gas to produce a pyrolysis vapor/sweep gas mixture. The sweep gas is hydrogen and at hydrogen partial pressure of 0.5-100 bar, so that any oxygen gas is preferably minimized to below 1 vol.%. The hydrogen atmosphere inhibits reactions of the tar formation process. The elevated hydrogen partial pressure reduces both the concentration of oxygenated free radicals and the dehydrogenation of aromatic ring and other compounds released by the thermally induced decomposition. The process severity is also reduced by minimizing localized temperatures in the reactor. Secondary tars are formed more easily with increased temperature. Thus the temperature of the pygas and char products is kept below 650 degrees C, such as by using a heating media to transfer heat to the biomass, where the heating media is heated in a separate, temperature-controlled process to a target temperature, such that the heating media temperature at time of contact with the biomass is not greater than 650 degrees C, thereby ensures the biomass pyrolysis products are not over heated. The preferred temperatures of the pyrolysis process greatly reduce the formation of any polyaromatic hydrocarbons and any dioxin precursor compounds compared with higher temperature pyrolysis or gasification methods known in the art; where the polyaromatic hydrocarbons and dioxin compounds are known toxins and carcinogens. Thus the method and the apparatus are useful for high efficiency conversion of biomass into a natural gas commodity. The product hydrocarbon can be used directly or can be injected into gas pipeline or liquefaction facility for contribution as widely distributed good. The renewable, sustainable, and carbon neutral nature of the biomass feedstock enhances the value of the exported product, especially when natural gas is used to generate electricity, generate heat, or as a transportation fuel. When used as fuel for natural gas combined cycle power generator the product results in high efficiency biomass to electricity system. The product can be exported across borders creating renewable energy industry from biomass.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a system for producing hydrocarbons from biomass that minimizes tar production to (less than 1%) based on mass of biomass processed and amount of tar produced, comprising: a fast pyrolysis device (30) operating at a process temperature of less than 650 degrees C for producing a pygas and char; an independent catalytic conversion device (42) downstream of the fast pyrolysis device operating at a process temperature of less than 650 degrees C and without addition of an oxidant for converting the pygas to hydrocarbons; and a hydrogen source (37) for adding hydrogen to the independent catalytic conversion device; and    (2) process for hydrogenating a material in a conversion reactor, involving: hydrogenating a first portion of the material in a conversion reactor to produce a hydrogenated product; separating a portion of the hydrogenated product in a separator downstream of the conversion reactor to provide a separated hydrogenated product portion; and recycling residual hydrogen and remaining hydrogenated material back to the conversion reactor, where the separated hydrogenated product portion is selected to control a hydrogen-to-material ratio in the conversion reactor.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic drawing of the biomass conversion plant.    Biomass feedstock (10)    Feed device (20)    Released steam (25)    Pressurized biomass stream (26)    Pyrolysis reactor (30)    Sweep gas stream of hydrogen (37)    Hot heating media stream (38)    Conversion section (42)    Transport mechanism (45)