The capacity of a biogas upgrading system based on the microalgae Chlorella sorokiniana was evaluated. A system composed of a photobioreactor connected to an absorption column was tested. Two continuous systems were operated with real biogas. One with biogas containing 1800-3500 ppm(v) of H2S, another one without H2S. The tested system provided 98% and 100% removal levels for CO2 and H2S, respectively. Removal of H2S was the result of oxidation to sulfate, as a consequence of the high concentration of dissolved oxygen. Comparison of both systems showed no signs of inhibition due to H2S presence in the biogas. It is concluded then that a microalgae-based biogas upgrading system would not only provide conditions for CO2 removal, but also for H2S oxidation. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.