The main objective of this investigation consists in the biogas purification coming from the anaerobic digestion of sludges in a wastewater treatment plant, in order to be used later as biofuel for vehicles. This article consists of the optimization of the biogas desulphurization. In our case, this process was achieved in a chemical way. Besides the scrubbing towers, the pilot plant used included filters of activated carbon at the end of the line. The H(2)S inflow concentrations were quite high. The effluent biogas from the scrubbing towers presented an H(2)S concentration less than I ppm and zero or undetectable values were obtained for up to 58 analyzed trace elements. (C) 2009 Elsevier Ltd. All rights reserved.