Oil palm empty fruit bunches (EFB) were pretreated by aqueous ammonia soaking for ethanol production. Pretreated EFB, which were pretreated at the optimal conditions of 60 degrees C, 12 h, and 21% (w/w) aqueous ammonia, showed 19.5% and 41.4% glucose yields during an enzymatic digestibility test for 96 h when using 15 and 60 FPU of cellulase, respectively. Using the pretreated EFB, simultaneous saccharification and fermentation for 168 h with 5% (w/v) glucan loading and 60 FPU of cellulase and 30 CBU of beta-glucosidase per gram glucan resulted in ethanol production of 18.6 g/L titer, 65.6% of theoretical maximum yield, and 0.11 g/L/h of productivity. (C) 2011 Elsevier Ltd. All rights reserved.