Ethanol can be produced from lignocellulosic materials in various ways. The main features of the different ethanol processes are outlined in Fig. 1. All processes comprise the same main components: hydrolysis of the hemicellulose and the cellulose to monomer sugars, fermentation and product recovery and concentration by distillation. The main difference between the process alternatives is the hydrolysis steps, which can be performed
by dilute acid, concentrated acid or enzymatically. Some of the process steps are more or less the same, independent of the hydrolysis method used. For example, enzyme production will be omitted in an acid-hydrolysis process; likewise, the recovery of acid