Qualidade e combustibilidade da madeira de clones de Eucalyptus spp.

Abstract

The demand for renewable energy is growing around the world. The participation of biomass, for the direct combustion of wood, charcoal, agricultural residues, among others, becomes more expressive. The purpose of this thesis was to evaluate the physical, chemical, thermal and energetic properties and to associate them with the wood combustibility of different clones of Eucalyptus spp., identifying the most suitable genetic materials for combustion. In chapter one, the clonal effect on growth characteristics, basic density, chemical composition, dry mass estimation and termal degradation of the wood was evaluated. It was verified that the volume and the estimated dry mass of wood were the variables that contributed the most for the distinction of the evaluated genetic materials and, therefore, they are decisive for its classification in the energetic use. Chapter two studied the thermal degradation behavior of wood, in oxidative atmosphere, and two main characteristic stages of the combustion were determined and differences were observed between the parameters of combustibility for the clones studied. Chapter 3 performed a broader and more detailed chemical characterization by quantifying soluble extractives in increasing polarity solvents, monosaccharides, lignins and ashes, as well as the phenolic composition of the extracts in ethanol/water (1:1) of the woods of eucalyptus clones. The monosaccharides identified were predominantly glucose and xilose. In all clones, steroids, fatty acids and aromatics were the most abundant lipophilic compounds. Phenolic compounds: flavonoids and tannins were quantified and identified. Chapter 4 evaluated the influence of molecular and immediate chemical composition, monomeric composition of the polysaccharides, lipophilic constituents present in the extract in dichloromethane and phenolic composition on the wood combustibility of the clones. The parameters: maximum rate of combustion, combustion index and ignition index, presented significant and inversely proportional relationships with the lignin, extractive soluble in ethanol, xilose; and significant and directly proportional relationships with holocellulose contents, extractives soluble in cold water, glucose and fatty alcohols. It was also observed that the flavonoids and tannins had a significant and directly proportional relationship with the temperature corresponding to the end of the combustion. The clones studied meet the specifications for energy use and can be highly feasible due to their physical, chemical, energetic and thermal characteristics.