Pretreatment of wastepaper using aqueous glycerol was investigated to enhance the enzymatic hydrolysis. The effects of four factors (solid/liquid ratio, glycerol concentration, acid concentration, and reaction time) on the dissolution yield, the removal of cellulose, hemicellulose and lignin, and the enzymatic digestibility were examined at 150 o C. The 1/8 of solid/liquid was determined to perform the reaction uniformly, and the 93% of glycerol concentration was found to be a minimum concentration to conduct the reaction under atmospheric pressure. Also, it was found that the acid concentration and reaction time were strongly related to the dissolution yield and the removal of cellulose, hemicellulose and lignin, but moderately to the enzymatic digestibility. At an optimum condition of 150 o C, 1 h and 1% acid concentration, 56% and 49% of hemicellulose and lignin, respectively, were removed, while only 4% of cellulose was removed. The enzymatic digestibility at this condition was 86%, meaning that 83% of the glucan present in the initial substrate was converted to glucose. Compared to glycerol with ethylene glycol as a pretreatment solvent, glycerol is much cheaper than ethylene glycol, but ethylene glycol is superior to glycerol in delignification.

Pretreatment of wastepaper using aqueous glycerol under high pressure was studied to enhance the enzymatic hydrolysis. The pretreatment was conducted over a wide range of conditions including temperatures of 150~170 o C, sulfuric acid concentrations of 0.5~1.5%, and reaction times of 30~90 minutes. After the effect of glycerol concentration on the pretreatment performance was investigated, 70% glycerol was selected. As glycerol concentration was increased, higher digestibility was achieved due to higher lignin removal. The optimum condition was found to be around 160 o C, 1%, and 60 minutes. At this condition, 60% and 35% of hemicellulose and lignin, respectively, were removed, while only 5% of cellulose was lost. The enzymatic digestibility was 76%, meaning that 73% of the glucan present in the initial substrate was recovered as glucose after enzymatic hydrolysis. Also, it was found that the temperature and acid concentration than the reaction time were more strongly related to the compositional removals and enzymatic digestibility.