Comparison of different methods for determining lignin concentration and quality in herbaceous and woody plant residues

aimsacid detergent lignin (adl), acetyl bromide (acbr), and cupric oxide oxidation (cuo) were compared as methods for determining lignin concentration and quality in plant residues. methods:these three methods were used to analyze 27 plant residues from different groups of species, i.e., legumes, crucifers, herbs, grasses, and trees. results:median lignin concentrations of the 27 plant materials were 4.5% adl and 6.0% acbr lignin, significantly exceeding the median of 2.1% cuo lignin. adl concentrations varied from 0.8 to 27.0%; those of acbr and cuo lignin ranged from 1.8 to 12.2% and from 0.6 to 9.7%, respectively. acbr lignin showed a significant negative, non-linear relationship with total n. in addition, the relationship of adl and cuo data was negatively affected by total n. conclusion:the adl method is simple and well reproducible, and large datasets are available for comparison. the acbr procedure is fast, with less interference from non-lignin products than adl. the cuo method is not interfered with by any other organic component in the plant material and gives additional information on the composition of the lignin. however, the release of phenolic units may be incomplete.