Three biomass-to-liquid processes (volatilization of cellulose, tar cleaning of organic products, and water-gas-shift of the gaseous effluent) have been combined into one autothermal catalytic reactor for the production of synthesis gas at millisecond residence times. Cellulose was reacted on the hot, catalytic bed of Rh-Ce/γ-Al2O3 catalyst on 1.3 mm α-Al2O3 spheres in the presence of O2, N2, and steam in a continuous flow fixed-bed reactor at 500-1100 °C. Complete fuel conversion to gases was observed for all experiments, in which N2/O2 ratio, S/C ratio, cellulose flow rate, and C/O ratio were varied. Steam addition increased the selectivity to H2 and decreased the selectivity to CO in agreement with water-gas-shift equilibrium. The process was demonstrated with ~80% selectivity to H2 at a synthesis gas ratio of H2/CO=2.3 with a pure oxygen gas feed at a fuel efficiency of ~75%. Carbon-free processing was explained by thermodynamic predictions for the formation of solid carbon, CS, at the observed experimental operating conditions.