Direct feeding of biogas to SOFC is theoretically feasible. However, several contaminants such as ammonia, siloxanes and chlorine compounds included in biogas can cause severely damage in the SOFC components. In this paper, the individual impact of 500 ppm NH3, 1 ppm D4 siloxanes and 250 ppm HCl on the performance of a single SOFC with W-Ni-Ce as anode directly fed by biogas has been investigated. Two singles cells (W-Ni-Ce/SDC/LSCF) were fabricated and tested at 750 degrees C. The first one was exposed to biogas with NH3 or siloxanes, and the second one to biogas with HCl. The electrochemical behaviour of cells was studied by I-V curves, impedance spectra, and under load demand in biogas with and without impurities. Post-test analyses of the anode/electrolyte interface were performed by SEM-EDS. The results showed that ammonia did not impact on the cell performance, whereas the presence of D4 siloxane caused the cell degradation by the formation of silica in the anode but the degradation rate is slower than SOFC with Ni-YSZ anode. The presence of HCl in biogas gave rise to important oscillations in the potential, and a performance loss under load demand that is probably due to adsorption-desorption processes of Cl on Ni and Ce surfaces. In addition, the presence of CO2 and H2O could improve the oxidation of Ni and CeO2-x reducing their catalytic activity; a severe corrosion in the stainless steel tubing and valves was also detected. Post-tests analysis suggested the formation of SiO2 deposits and Cl adsorbed on Ni and Ce particles. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.