Optimizing acid-hydrolysis: a critical step for production of ethanol from mixed wood chips

Ethanol can be produced from renewable lignocellulosic materials such as various types of natural woods. The cellulose contents of wood can be converted to ethanol in a two-step process where acid-hydrolysis converts cellulose to glucose sugars by hydrolysis (saccharification) and the resulting sugars can be converted to ethanol by fermentation. The main challenge of producing fuel ethanol from renewable lignocellulosic biomass through acid-hydrolysis and fermentation is overcoming the cost-limiting factors associated with various stages of this technology. In this study, sugar recovery rates from a mixture of wood chips were investigated through three sets of acid-hydrolysis experiments. Wood chips were sorted to include equal ratios (by weight) of softwood and hardwood. Acid concentration and the heating period were the two main factors affecting dextrose yields. It was found that with the use of 26% by weight sulfuric acid, highest dextrose yields could be reached within 2 h of heating time. This corresponds to overall conversion efficiency of mixed wood chip cellulose to dextrose in the range of 78–82% based on theoretical values.