NOVELTY - Producing (I) at least one product from gaseous substrate, comprises: converting at least a portion of a biomass feedstock to a gaseous substrate comprising carbon monoxide by a biomass liquefaction process of pyrolysis or torrefaction; passing at least a portion of gaseous substrate to a bioreactor comprising a culture of at least one e.g. carboxydotrophic acetogenic microorganism to produce at least one fermentation product and a waste stream; separating at least a portion of the second biomass from the waste stream; and passing a portion of the second biomass to liquefaction zone.    USE - The method is useful for producing product from gaseous substrate, where the fermentation product is ethanol, acetic acid or 2,3-butanediol (claimed).    ADVANTAGE - The method provides high quality end-products without the need for costly storage or transport of the pyrolysis oil and without the requirement for high purity hydrogen and stored for use in the pyrolysis oil upgrading process.    DETAILED DESCRIPTION - Producing (I) at least one product from a gaseous substrate, comprises: converting at least a portion of a biomass feedstock to a gaseous substrate comprising carbon monoxide by a biomass liquefaction process of pyrolysis or torrefaction, where the process carried out in a liquefaction zone; passing at least a portion of the gaseous substrate to a bioreactor comprising a culture of at least one carboxydotrophic acetogenic microorganism, and an aerobically fermenting at least a portion of the gaseous substrate to produce at least one fermentation product and a waste stream comprising a second biomass; separating at least a portion of the second biomass from the waste stream; and passing a portion of the second biomass to the liquefaction zone. INDEPENDENT CLAIMS are also included for:    (1) producing (II) at least one product from a gaseous substrate, comprising: passing a biomass feedstock to a pyrolysis zone, operated at conditions to produce a gaseous substrate comprising carbon monoxide, carbon dioxide and hydrogen, and at least one pyrolysis product comprising pyrolysis oil and char; passing at least a portion of the gaseous substrate to a bioreactor comprising a culture of at least one carboxydotrophic acetogenic microorganism, and an aerobically fermenting at least a portion of the gaseous substrate to produce at least one fermentation product, a waste stream comprising a second biomass and an exit gas stream comprising hydrogen; separating at least a portion of the second biomass from the waste stream; and passing a portion of the second biomass to the pyrolysis zone; and    (2) producing (III) at least one product from a gaseous substrate, comprising; passing a biomass feedstock to a torrefaction zone to produce a torrefied biomass; passing the torrefied biomass to a pyrolysis zone to produce a gaseous substrate comprising carbon monoxide, pyrolysis oil and char; passing at least a portion of the gaseous substrate to a bioreactor comprising a culture of at least one carboxydotrophic acetogenic microorganism, and an aerobically fermenting at least a portion of the gaseous substrate to produce at least one fermentation product, a waste stream comprising a second biomass and an exit gas stream comprising hydrogen; separating at least a portion of the second biomass from the waste stream; passing the exit gas stream to a separation zone operated at conditions to provide a hydrogen rich stream; passing a portion of the second biomass to the torrefaction zone; and passing the pyrolysis oil and the hydrogen rich stream to a hydrogenation zone operated at conditions to produce a hydrogenated product.