Chemical composition

The main components of biomass are cellulose, hemicelluloses, and lignin:

  • Cellulose or carbohydrate is the principal constituent of wood and other biomass and forms the structural framework of wood cells. It is a polymer of glucose with a repeating unit of C6H 10O5 strung together by β-glycosidic linkages. The β-linkages in cellulose form linear chains that are highly stable and resistant to chemical attack because of the high degree of hydrogen bonding that can occur between chains of cellulose. Hydrogen bonding between cellulose chains makes the polymers more rigid, inhibiting the flexing of the molecules that have to occur in the hydrolytic breaking of the glycosidic linkages.
  • Hemicellulose consists of short, highly branched chains of sugars. In contrast to cellulose, which is a polymer of only glucose, a hemicellulose is a polymer of five different sugars.It contains five-carbon sugars (usually D-xylose and L-arabinose), six-carbon sugars (D-galactose, D-glucose, and D-mannose) and uronic acid. 
  • Lignin is the major non-carbohydrate, polypenolic structural constituent of wood and other native plant materials that encrusts the cell walls and helps in cementing the cells all together [5].