The present work explores the combined production of hemicellulose-derived carbohydrates and an upgraded solid residue from wheat straw using a dilute-acid pretreatment at mild temperature. Dilute aqueous HCl solutions were studied at temperatures of 100 and 120 degrees C, and they were compared to dilute FeCl3 under the same conditions. Comparable yields of soluble sugars and acetic acid were obtained, affording an almost complete removal of pentoses when using 200 mM aqueous solutions at 120 degrees C. The solid residues of pretreatment were characterized showing a preserved crystallinity of the cellulose, and a almost complete removal of ash forming matter other than Si. Results showed upgraded characteristic of the residues for thermal conversion applications compared to the untreated wheat straw. (C) 2011 Elsevier Ltd. All rights reserved.