NOVELTY - Producing low-oxygenate bio-oil comprises: subjecting a biomass feedstock (110) to a slow pyrolysis to produce a gaseous oxygen containing compounds and a low-oxygen biomass feedstock having an oxygen removal degree of at least 0.5; removing the gaseous oxygen containing compounds from the low-oxygen biomass feedstock; and subjecting the low-oxygen biomass feedstock to a flash pyrolysis to produce, at a conversion rate of at least 70 wt.%, a bio-oil having a oxygenate content of less than 25 wt.%.    USE - The method is useful for producing low-oxygenate bio-oil, which is useful for treating the biomass feedstock.    ADVANTAGE - The method provides low-oxygenate bio-oil having improved physical and chemical properties, in a simple and economical manner.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a low-oxygenate bio-oil production plant (100) comprising a slow pyrolysis reactor (120) configured to receive a biomass feedstock and to produce a low-oxygen biomass feedstock and the gaseous oxygen-containing compounds, a flash pyrolysis reactor (130) operationally coupled to the slow pyrolysis reactor and configured to receive the low-oxygen biomass feedstock and to produce a bio-oil, a control device having a digital storage medium, where the control device is operationally coupled to the slow pyrolysis reactor and the flash pyrolysis reactor, and the storage medium stores instructions for a control elements to allow for (a) slow pyrolysis of a biomass feedstock in the slow pyrolysis reactor to so produce a many gaseous oxygen-containing compounds and a low-oxygen biomass feedstock having an oxygen removal degree of at least 0.5, and (b) flash-pyrolysis of the low-oxygen biomass feedstock in the flash pyroiysis reactor to produce, at a conversion rate of at least 70 wt.%, a bio-oil having a oxygenate content of less than 25 wt.%;    (2) a slow-pyrolyzed low-oxygen biomass having an oxygen removal degree of at least 0.5 as compared to the same biomass prior to slow-pyrolysis; and    (3) treating a biomass feedstock comprising subjecting the biomass feedstock to a slow pyrolysis to produce a solid phase low-oxygen biomass feedstock and a gas phase comprising a gaseous oxygen-containing compounds, where the low-oxygen biomass feedstock has an oxygen removal degree of at least 0.5, and a carbon loss from the low-oxygen biomass feedstock through the gas phase is less than 20 mole.%.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a two-stage pyrolyzer.    Low-oxygenate bio-oil production plant (100)    Biomass feedstock source (110)    Slow pyrolysis reactor (120)    Hydrogen source (126)    Flash pyrolysis reactor. (130)