The aim of the paper is to provide thermodynamic evaluations for the production of synthetic natural gas from biomasses in order to determine parameters such as purity and productivity obtained with different configurations process. Analysis results showed that, fixed biomethane productivity, with a single stage of methanation, the use of a water gas shift reactor (WGS) prior to the methanation stage, may contribute to increase of purity in methane, although modest, increasing from 65% to 80 vol.% The final effect is the increase of the heating value of SNG from 23 to 26 MJ/Nm(3). Numerical results showed that with a single stage methanation for SNG production, in isothermal conditions, it is possible to obtain a productivity of about 0.30 Nm(biomethane)(3)/Nm(syngas)(3) with a purity of 80 vol.% but with different complications for the process, such as introduction of WGS stage and/or double CO2 adsorption stage. Other evaluations are proposed in the paper in order to improve the performance of the process, such as the use of isothermal reactor although more difficult to manage compared to the pseudo adiabatic configuration plant. Using isothermal configuration it is possible to have higher conversion levels with smaller dimensions plant and therefore it may be an alternative to conventional systems at the end to create demo as driving force for technological development. (C) 2014 Elsevier Ltd. All rights reserved.