Table 3.

Classification of different types of lignin depending on the amount of para-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) sub-units.

Type	Grass Lignin	Softwood	Hardwood
H	5–35%	<5%	0–8%
G	35–80%	>95%	25–50%
S	20–55%	0%	45–75%

Proportion of different monolignols in lignin of different plants source. Adapted from [78,79,80].