Comparative study of the thermal behavior of wood and bark of young shoots obtained from an energy plantation

Abstract

We have performed thermogravimetry/mass spectrometry (TG/MS) analysis of young wood samples from a short rotation forestry plantation to get information about their thermal behavior. Poplar ( Populus × euramericana, Populus × interamericana), willow ( Salix alba) and black locust ( Robinia pseudoacacia) species have been studied. The ratio of wood and bark in these young shoots is significantly different from that of an older wood. That is why great emphasis has been put on the comparative study of the decomposition characteristics of wood and bark. Considerable differences have been found in these investigations: more volatiles are produced from wood than from bark; the temperature range and the rate of decomposition also differ. The TG/MS results are interpreted in terms of the chemical composition characterized by Klason lignin and ash content. One of the main differences between the chemical composition of wood and bark is the amount of inorganic ions: the mineral matter content is significantly higher in the bark than in the wood. We have pretreated the samples with a hot water washing procedure in order to eliminate a significant part of these inorganic components and investigate their effects on the thermal decomposition of the samples. The results imply that the thermal behavior of wood and bark are still considerably different after the elimination of some of the inorganic components, however, the macromolecular components decompose at similar temperatures in wood and bark. Since we had a large number of samples and TG/MS data, we have employed a chemometric tool, principal component analysis (PCA) to help the evaluation of the results and the comparison of the samples.