Classification of Lignin According to Chemical and Molecular Structure

The commercial trade in isolated lignins generated in conjunction with the fractionation of biomass into constitutive components, including pulp and paper and saccharification/fermentation processes, requires the adoption of standard analytical techniques by both suppliers and users of such products. Simple, reliable, quantitative, and widely accepted techniques include elemental analysis, functional group analysis, analytical degradations, various spectroscopic techniques, molecular weight analysis, and thermal analysis. These techniques are capable of elucidating the chemical composition of repeat units; the nature of intermonomer bonds; molecular weights and weight distributions; and the potential for inter- and intramolecular interactions. Several aspects of this classification methodology are reviewed.