This study compares the efficacy of soaking and percolation pretreatments with alkaline solutions for lignocellulosic biomass. The pretreated biomasses underwent enzymatic hydrolysis. Various biomasses such as rice straw and barley were pretreated by soaking processes in various alkaline solutions including sodium hydroxide, potassium hydroxide, aqueous ammonia and sodium carbonate. The enzymatic digestibility of rice straw and barley that had been pretreated by soaking in aqueous ammonia was 85% and 95%, respectively. Eucalyptus residue, Larix leptolepis and Pinus rigida exhibited relatively low enzymatic digestibility in the range of 3.2%-8.3%. Nevertheless, the enzymatic digestibility of pretreated eucalyptus residue was increased by five times compared to that of the initial biomass. In the pretreatment of eucalyptus residue, delignification was more than doubled with percolation pretreatment compared to soaking pretreatment. The enzymatic digestibility of the percolation pretreated eucalyptus residue was increased 12 times. (C) 2012 Elsevier Ltd. All rights reserved.