The aim of this work is to evaluate the performance of PEEK membrane modules modules membrane with two different configurations plant in order to obtain low pressure biomethane usable directly in the secondary grid injection with a pressure lower than 10 bar. Two configurations were studied: high recovery configuration and high power configuration and for each one an energetical evaluation was carried out. In each one configuration biomethane purity was fixed at 94 vol.% and the experimental tests were carried out fixed a simulated biogas fed at 50 kg/h with a methane content of about 55 vol.%. The experimental tests allowed to establish the feasibility of the biomethane production at low pressure for the secondary grid injection in a polygeneration plant: power, thermal energy and biomethane each one with a productivity that could be regulate by changing parameters of the process. (C) 2015 Elsevier Ltd. All rights reserved.