Cumulative pretreatments methods were evaluated for delignification ability and enzymatic digestibility using miscanthus (MxG), empty palm fruit bunch (EFB) and typha grass as feedstocks. Despite their close chemical composition, the three feedstocks unveiled quite different behavior under the same condition of pretreatment. Characterization of ethanol organosol lignins extracted from the three feedstocks by C-13 NMR and FTIR revealed information concerning S/G/H ratios which was important to rationalize the differences among the feedstock behavior. The S/G/H ratios for MxG, EFB and typha, were established to levels of similar to 52/44/4, similar to 68/30/2 and similar to 46/27/27 respectively. The xylans hydrolytic susceptibility were a major cause of difference in behavior of feedstock during the pretreatment process. The influence of the presence of naphthol during autohydrolysis on the delignification ability was studied. A good relationship was observed between S + H/G ratio and the scavenging effect of naphthol. (C) 2012 Elsevier Ltd. All rights reserved.