NOVELTY - The method comprises performing oxycombustion of a carbon-based feedstock to create a cogeneration of electricity and heat, performing high-temperature electrolysis (HTE) of water from the heat produced according to the oxycombustion step, and performing reverse water-gas shift (RWGS) reaction from carbon dioxide produced according to the oxycombustion step and from hydrogen produced according the HTE step. The HTE step is carried out from the electricity produced according to the oxycombustion step. A part of oxygen produced by the HTE step is used as combustive of the oxycombustion step.    USE - The method is useful for performing thermochemical conversion of a carbon-based feedstock such as biomass to synthesis gas containing hydrogen and carbon monoxide, which are useful for obtaining liquid fuels (all claimed).    ADVANTAGE - The method is capable of performing thermochemical conversion of a carbon-based feedstock in an energy efficient and cost-effective manner, and improving yield of gas synthesis.    DETAILED DESCRIPTION - The method comprises performing oxycombustion of a carbon-based feedstock to create a cogeneration of electricity and heat, performing high-temperature electrolysis (HTE) of water from the heat produced according to the oxycombustion step, and performing reverse water-gas shift (RWGS) reaction from carbon dioxide produced according to the oxycombustion step and from hydrogen produced according the HTE step. The HTE step is carried out from the electricity produced according to the oxycombustion step. A part of oxygen produced by the HTE step is used as combustive of the oxycombustion step, and the remaining part of the oxygen is recovered. The water produced by the RWGS step is recycled and injected as a starting material of HTE step. The method further comprises performing gas cleaning obtained according to the RWGS step so as to extract hydrogen and carbon monoxide. The cleaned carbon dioxide according to the cleaning step is injected as a starting material to the RWGS step. The water output from the cleaning step is recycled and injected as a starting material of the HTE step. The carbon monoxide and hydrogen output from the cleaning step are injected as starting materials to carry out a Fischer Tropsch (FT) synthesis to obtain a liquid fuel. The water output from of the FT synthesis is recycled and injected as a starting material of HTE step. The gas generated from the FT synthesis is injected as a starting material of the oxycombustion step. The heat generated by the FT synthesis is used for a production of steam in an entry of the HTE step. The carbon-based feedstock is biomass, where a water content of biomass is lower than 50%.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic flow diagram of a method for performing thermochemical conversion of a carbon-based feedstock (Drawing includes non-English language text).