The conversion of lignocellulosic material to monomeric sugars (e.g. C5 and C6 sugars) is more difficult than the conversion of starch. There are numerous features, which have to be considered additionally, compared to bioethanol production using sugar- or starch-based feedstocks. One of them is an efficient conversion of cellulose and hemicellulose to monomeric sugars, as well as an optimal fermentation of C5 and C6-mixed sugar hydrolysat, containing inhibitory compounds.
A big advantage of biofuel production using lignocellulosic materials is the opportunity to create a biorefinery. Value-added co-products (by-products) e.g. lactic acid, which can be processed into plastics or other products, as well as the non-carbohydrate components of lignin, which can be used in value-added applications are produced.
The process of bioethanol production using lignocellulosic materials consists of 4 major operations steps:
4. Product separation/distillation
Figure 1: Schematic demonstration of bioethanol production using lignocellulosic materials (source: adapted from Hahn-Hagerdal et al. 2006).