Assessing proximate composition, extractive concentration, and lignin quality to determine appropriate parameters for selection of superior Eucalyptus firewood

Abstract

Planted Eucalyptus forests are the largest potential energy source in Brazil. They supply energy for several industrial sectors, so a detailed quality assessment of this biomass is required. Although many important parameters have been evaluated, few studies have considered the effect of lignin composition in firewood, as the amount of syringyl (S) and guaiacyl (G) units on thermogravimetric characteristics. The aim of this research was to evaluate the energetic characteristics of Eucalyptus clones and identify the effect of chemical composition and lignin quality on the resistance to thermal degradation of firewood. The study was performed with 14 clones of Eucalyptus from a planted forest. Plant material was analyzed for energy productivity, heating value, ash content, proximate and elemental compositions, and thermal characteristics. Methods to determine chemical composition were proximate analysis, soluble extractives in acetone and quantification of lignin contents. Chemical composition and the quantity of G units influenced the combustion performance. The soluble extractives in acetone and the higher proportion of G units in lignin resulted in an increase in thermal stability and prolonged the combustion time. The mass of the structural unit G per kilogram of dry wood is a good parameter to classify Eucalyptus clones for heat generation. G units ranged from 19.61 to 25.68 g kg−1 (dry wood). The clone 1037 (Eucalyptus sp.) had superior combustion performance and the highest energetic productivity (2921.61 MJ tree−1) of the 14 clones studied.