Insights in quantitative indexes for better grouping and classification of Eucalyptus clones used in combustion and energy cogeneration processes in Brazil

Abstract

The influence of the lignin macromolecule composition, extractives, volatile matter (VM), and fixed carbon (FC) contents on the reactivity and easiness of wood combustion is not fully understood, especially concerning species from fast-growing plantations. This study aims to close this scientific gap revealing the wood chemical composition effects on the combustibility of Eucalyptus clones. Moreover, we proposed new quantitative indexes that allow suitable grouping of genetic materials for energy purposes. The lignin, acetone-soluble extractives, VM, FC, and ash contents, as well as the ratio syringyl (S)/guaiacyl (G), were determined. The thermogravimetric analyses provided the combustion parameters. The characteristics that most contributed to the grouping of Eucalyptus clones were energy productivity (GJ ha−1 and GJ tree−1), energy density (GJ m−3), acetone-soluble extractives (% based on dry mass - db), VM (% db), and the maximum rate of combustion (% min−1). Clones with G units ≤20 g kg−1 db, acetone-soluble extractives ≤1.0% db, and FC ≤ 16% db had easier ignition and better reactivity during the burning. Clones with VM/FC ratio ≥5.0 showed maximum combustion rate ≥8.0% min−1 and acetone-soluble extractives ≤1.1% db. The findings of this investigation are useful to managers’ decision-making and contribute to the selection and rational use of the wood for energy purposes.