Influence of extractives content and lignin quality of Eucalyptus wood in the mass balance of pyrolysis process

Abstract

Several studies have highlighted the importance of the chemical composition of Eucalyptus woods in the generation of thermal energy and charcoal production. However, the influence of wood chemical constituents on the pyrolysis mass balance is still not sufficiently clear. This paper brings new insights about the influence of extractives and guaiacyl (G) to syringyl (S) ratio of lignin macromolecule in the carbon, hydrogen, and oxygen balances of the pyrolysis process. Thus, the aim of this research was to investigate the effect of the wood quality of genotypes of Eucalyptus on the carbonization mass balances. Ultimate analysis, structural chemical constituents, and lignin composition analyses were carried out in 14 clonal materials of Eucalyptus spp. at 81 months of age. After pyrolysis, the ultimate analysis of charcoal and the carbonization mass balance was also investigated. The findings show a positive relationship between the percentages of carbon and hydrogen retained in the charcoal with the lignin content and its composition. E. camaldulensis (clone 1025) and E. grandis hybrids (clone 1039) presented better wood quality for charcoal production, due to the results of gravimetric yield (35.7%), retained carbon (59.6%), and retained hydrogen (20.2%) after pyrolysis. In addition, these genetic materials stood out for the high values of lignin (32.0%), extractives soluble in acetone (2.4%), and mass of guaiacyl per kg of dry wood (27.2 g kg-1) associated with the low S/G ratio (2.5). The extractives content and lignin composition must be simultaneously analyzed to improve the Eucalyptus clones classification for charcoal production.