Computer simulations of organosolv pulping processes (ethanol-water and ethylene glycol-water mixtures) using commercial simulation software (ASPEN PLUS) have been developed in order to design the process and to establish its key points (product and byproduct mass flow balances, energy analysis, and solvent recovery degree) as well as to analyze operation conditions. Laboratory experiments, in which a deciduous wood called leucaena (Leucaena leucocephala) was used as raw material, were carried out to obtain input data for the simulation. The proposed process flow sheets allow the recovery and recycling of a high percentage of used solvents (97 wt % ethanol and 88 wt % ethylene glycol), which represent a reduction of 66 and 59 wt % of fresh solvent input for ethanol and ethylene glycol, respectively.