Pre-treatment methods for biomass prior to conversion into fuels and chemicals can be classified into physical, thermal, biological, and chemical, or any combination of these methods. The selection of appropriate pre-treatment should be based on the aspects to enhance the biomass properties that increase the efficiency of the conversion process.

Biomass contains varying amounts of cellulose (40-60%), hemicellulose (20-40 %), lignin (10-25 %), and small amount of extractives. These wide range of these fractions lead to different thermal behavior and digestability. Hemicellu — lose, which is the most reactive compound in biomass, decomposes at relatively low temperature, that is, within the range of 225-325 °C. Meanwhile, cellulose degrades between 305 and 375 °C and lignin decomposes gradually over the temperature range of 250-500 °C [5].

The four methods reviewed in this chapter are physical, thermal, biological, and chemical pre-treatments. Physical and thermal treatments are mainly to remove mois­ture; hence increase the energy density of that particular biomass. The chemical and biological treatments are performed to de-polymerize lignin.