[AMIM][Cl] dissolved Eucalyptus grandis, southern pine sawdust (particle size 0.1-2 mm) and Norway spruce thermomechanical pulp almost completely in 5 h at 120°C. IL pretreatment of southern pine improved the glucose yield after enzymatic hydrolysis from 7 to 17 wt%. But the improvement of the glucose yield after IL pretreatment was found to decrease with increasing wood density. Higher density wood (Eucalyptus grandis) requires an IL pretreatment at a higher temperature than low-density wood (southern pine) to achieve the same pretreatment efficiency [31]. Hardwoods such as red oak usually have a higher density than softwoods such as pine, but softwoods also tend to have higher lignin content. Lignin in softwoods is also rich in guaiacyl units, while lignin in hardwoods is a mixture of guaiacyl and syringyl units [36]. Similarly, wheat straw (low lignin content) could be dissolved in [EMIM][OAc] with acetic acid at a lower temperature (100°C) than pine wood (higher lignin content) (120°C) for the same particle size (<1 mm) [47].