Lignocellulosic biomass can be biochemically transformed into different bioen­ergy products which are either liquid (bioethanol, biobutanol, 1,2-biobutanol, branched liquid alcohol mixtures) or gaseous (biogas, biohydrogen) and can be used as replacement for conventional combustible fuels used for electricity genera­tion, transport and various heating applications. Table 7.3 lists the lignocellulose source (energy crops or residues generated by the forestry industry and pulp mills), the technology for biological transformation and associated products of the transformation.

Lignocellulose conversion into biofuels through biochemical transformation involves the following steps:

• Pretreatment of biomass for enhanced accessibility and digestibility by enzymes

• Hydrolysis of cellulose and hemicellulose to sugars and/or organic acids

• Microbial transformation of sugars/acids into designated biofuels

• Product recovery

From the abovementioned bioenergy products, bioethanol and biogas have been the most extensively studied and are nearest to commercialization, while butanol is receiving increased attention. The conversion technologies involved as well as biomass specifications are described in more detail in the following sections.