Pretreatment with three green cellulose solvents, N-methylmorpholine-N-oxide (NMMO), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), and 1-butyl-3-methylimidazolium acetate ([BMIM][OAc]) were used for improvement of ethanol production. Spruce chips and powder were pretreated at 120 degrees C for 1, 3, and 15 h. In order to investigate the efficiency of the pretreatments, the pretreated materials were subjected to enzymatic hydrolysis at 45 degrees C for 72 h, followed by fermentation with Saccharomyces cerevisiae at 32 degrees C for 24 h. The best results were obtained from 15 h pretreatment with [EMIM][OAc]. The ethanol yield from the untreated spruce chips and powder were 2.7% and 9.7% of the maximum theoretical yield, respectively, whereas pretreatment of these materials with [EMIM][OAc] improved the ethanol yield to 66.8% and 81.5%, respectively. (C) 2012 Elsevier Ltd. All rights reserved.