Analysis of Biomass Composition Using High-Resolution Thermogravimetric Analysis and Percent Bark Content for the Selection of Shrub Willow Bioenergy Crop Varieties

Rapid determination of biomass composition is critical for the selection of shrub willow varieties with optimized biomass properties for conversion into fuels or chemicals. In order to improve the process for identifying and selecting shrub willow clones with distinct biomass composition, high-resolution thermogravimetric analysis (HR-TGA) was developed as a rapid, low-cost method for analyzing large numbers of willow biomass samples. In order to validate the HR-TGA method, bulk biomass collected from 2-year-old stems of a selected set of 25 shrub willow clones was analyzed using traditional wet chemistry techniques in addition to HR-TGA. The results of the wet chemistry and the HR-TGA method were compared using regression analysis resulting in R-squared values above 0.7 for the three main wood components, cellulose, hemicellulose, and lignin. Bark was removed from duplicate stem samples of the same clones, the proportion of bark was determined, and the debarked wood was used for HR-TGA analysis of composition. While there were significant differences in the proportions of lignin and cellulose in debarked wood compared to bulk biomass, as well as significant differences in bark percentage among clones, there was no correlation between bark percentage and bulk biomass component analysis. This work validates the effectiveness, precision, and accuracy of HR-TGA as a reasonably high-throughput method for biomass composition analysis and selection of shrub willow bioenergy crop varieties.