Influence of extractives on the analysis of herbaceous biomass

The consequences of extracting switchgrass, corn stover, and fescue feedstocks with either 95% ethanol or hot water prior to the chemical characterization of the feedstock have been determined. Glycans (glucan and xylan), Klason lignin, acid soluble lignin, uronic acids, acetyl groups, protein, and ash analyses were done on each feedstock. Extraction with 95% ethanol or hot water significantly reduced the measured Klason lignin values of all the feedstocks. Ethanol extractions reduced the apparent glucan content of two of the feedstocks, fescue and switchgrass. Extractions with hot water reduced the apparent glucan content of all the feedstocks. The apparent content of other components in the feedstock, such as ash and protein, was also reduced as a result of doing solvent extractions. The results indicate that more accurate estimates of the true Lignin and cellulose content of a feedstock are obtained if extractives are removed from the feedstock prior to the analysis. However, in some cases the analysis of extracted feedstocks resulted in lower values for the total carbohydrate content of those feedstocks. This parameter is critical when evaluating these feedstocks for biomass-to-ethanol processes.