Olive tree biomass (OTB) is an agricultural residue which can be used as raw material for bioethanol production. OTB was pretreated with 0.05-0.275 M FeCl3 solutions at 120-180 degrees C for 0-30 min. Enzymatic hydrolysis yields were used for assessing pretreatment performance. Optimum FeCl3 pretreatment conditions were found to be 152.6 degrees C, 0.26 M FeCl3 for 30 min. Under such conditions, 100% of hemicellulose was removed, and enzymatic hydrolysis of pretreated solids resulted in a yield of 36.6 g glucose/100 g of glucose in the raw material. Hemicellulosic sugar recovery in the prehydrolysate was 63.2%. Results compare well with those obtained by other pretreatment strategies on the same raw material, confirming FeCl3 solutions as a new, feasible approach for bioethanol production. (C) 2012 Elsevier Ltd. All rights reserved.