Lignin in straw of herbaceous crops

Biomass from herbaceous crops is the largest renewable source for the production of bioproducts and biofuels. The available information about lignins in straw of herbaceous crops is scattered and the available reviews generally address wood lignins. This review is focused on the structural characteristics and separation of lignin in the straws of corn, wheat, rice and flax, and it is the first attempt to generalize the information about lignin structure of important herbaceous crops and processes for the separation of lignin from hemicellulose and cellulose in lignocellulosic crop residues. The differences in lignin structures and processes for the fractionation of the major components of straw are highlighted, and the conversion of lignin into value-added products is addressed.