In the last years the research activities on biomass valorisation (mainly residues from urban and agricultural activities) have been intensified. Biomass is an abundant resource for energy generation and its extensive utilization may make possible to fulfil the goals determined by the national and international regulations about renewable sources and greenhouse gas emissions. In this work, simulations are carried out using ASPEN PLUS for an integrated process to produce liquid fuels from biomass in a self-sustainable energetic regime (thermal and electric) and several process factors have been considered. The process initially combines a primary pyrolysis reactor associated to a (char + gases) gasification unit in order to optimize the biomass use, followed by downstream processes to enhance the quality of final liquid fuel. The factors studied were the composition of the biomass, the primary (or pyrolytic) liquid yield, the composition of the liquid fuel, as well as the amount of the oxidant and steam used in the primary char-gasifier reactor. The use of a simplified model for liquid fuel composition let us to stablish a range of operational conditions in which both thermal and electric balance of the process are favourable. In this sense, the maximum extraction of liquid fuel was found around 20-25% by working at 10-25% of O-2 (as pure oxygen or air) and 15-45% of steam in the gasifier and fulfilling self-sustainable process condition, while biomass should possess C/O weight ratios >= 1.