The use of plant residues for energy purposes is already a reality, yet in order to ensure suitability and recommend a given material as being a good energy generator, it is necessary to characterize the material through chemical analysis and determine its calorific value. This research aimed to analyze different residues from plant biomass, characterizing them as potential sources for energy production. For the accomplishment of this study, the following residues were used: wood processing residue (sawdust and planer shavings); coffee bean parchment and coffee plant stem; bean stem and pod; soybean stem and pod; rice husk; corn leaf, stem, straw and cob; and sugar cane straw and bagasse. For residue characterization the following analyses were done: chemical analysis, immediate chemical analysis, calorific value and elemental analysis. All procedures were conducted at the Laboratory of Forest Biomass Energy of the Federal University of Lavras. In general, all residues showed potential for energetic use. Rice husk was found to have higher lignin content, which is an interesting attribute as far as energy production is concerned. Its high ash content, however, led to a reduction in calorific value and fixed carbon. The remaining residues were found to have similar energetic characteristics, with corn cob showing greater calorific value, followed by coffee plant stem, both also containing higher levels of carbon and fixed carbon. A high correlation was found of higher calorific value with volatile materials, carbon and hydrogen contents.

Babassu is considered the largest native oil resource worldwide and occurs naturally in Brazil. The purpose of this study was to evaluate the potential of babassu nut residues (epicarp, mesocarp and endocarp) for bioenergy use, especially for direct combustion and charcoal production. The material was collected in the rural area of the municipality of Sítio Novo do Tocantins, in the state of Tocantins, Brazil. Analyses were performed considering jointly the three layers that make up the babassu nut shell. The following chemical characterizations were performed: molecular (lignin, total extractives and holocellulose), elemental (C, H, N, S and O), immediate (fixed carbon, volatiles and ash), energy (higher heating value and lower heating value), physical (basic density and energy density) and thermal (thermogravimetry and differential thermal analysis), besides the morphological characterization by scanning electron microscopy. Babassu nut residues showed a high bioenergy potential, mainly due to their high energy density. The use of this biomass as a bioenergy source can be highly feasible, given their chemical and thermal characteristics, combined with a low ash content. Babassu nut shell showed a high basic density and a suitable lignin content for the sustainable production of bioenergy and charcoal, capable of replacing coke in Brazilian steel plants.

The near infrared spectroscopy (NIRS) has shown a rapid and accurate technique for evaluation of materials of biological origin. The objective of this study was to evaluate the ability of the near infrared (NIR) spectroscopy associated to the Principal Component Analysis (PCA) for the separation of carbonization processes and identification of the origin of the woods used in the carbonizations. Hence, the charcoal of seven species of Eucalyptus and twenty native species from the Cerrado (savannah) of Minas Gerais, Brazil were investigated. The Eucalyptus wood was carbonized in a laboratory furnace and in a 190 m³ industrial rectangular kilns while the wood of native vegetation was carbonized only under laboratory conditions. The samples were grinded for NIR spectra acquirement. The NIR spectra were analyzed by PCA but no cluster were identified allowing discrimination between charcoal produced from native and from Eucalyptus wood. However, the cluster formed in the PCA when using the first derivative NIR spectra permitted to distinguish charcoal produced in different processes of carbonization. Two groups of data for charcoal produced in the industrial rectangular kilns were also observed, suggesting heterogeneity in the carbonization process.

Mechanical properties studies of wood usually involve destructive wood assessments, with time-consuming tests that use large amounts of resource (wood). Although this is not a limiting factor, it could be attenuated by the use of a nondestructive technique known as near infrared spectroscopy (NIRS). This technique has been applied to evaluate compounds containing C-H, N-H, S-H or O-H bonds, and involves quick analyses and can be applied to process control tasks. The objective of this work is to use the NIRS technique to obtain calibrations for mechanical properties of Eucalyptus sp. wood. A natural E. urophylla hybrid at age 7 was used as obtained from V&M Florestal crops. Spectra were measured directly in solid wood (radial, tangential and transverse faces) and in ground wood, in diffuse reflectance mode, using a Bruker spectrometer in the 800 to 1,500 nm range. The NIRS technique proved suitable to estimate modulus of elasticity in solid wood, with values r=0.91 and RPD=2.6, and in ground wood, with values r=0.87 and RPD=2.0. Modulus of rupture and compressive strength presented r values below 0.9. First and second derivative pretreatments provided a slight increase in correlation values for the properties in question. Calibrations for different plank faces did not present a defined variation pattern. Solid wood and ground wood presented similar correlation values for all properties. (Résumé d'auteur

Durante a produção de carvão vegetal, diferentes produtos são formados. Esses produtos são resultantes, principalmente, da temperatura final de carbonização. Sendo o carvão vegetal um dos principais insumos na produção de ferro gusa no Brasil, no presente trabalho, objetivou-se avaliar a influência da temperatura final de carbonização no rendimento dos produtos gerados, e também verificar a influência da posição radial e longitudinal de amostragem nos rendimentos de cada produto. Para isso, foram retiradas amostras da posição interna e externa ao longo do raio e também de três diferentes alturas a partir de quatro árvores de Eucalyptus microcorys. As amostras foram carbonizadas em forno elétrico experimental adaptado, com condensador resfriado à água e frasco coletor de materiais voláteis condensáveis. As temperaturas finais de carbonização foram de 500, 600, 700, 800 e 900ºC. Em seguida, foram calculados os rendimentos gravimétricos em carvão, líquido pirolenhoso e gases não condensáveis. Os resultados mostram que não houve diferença de rendimento gravimétrico em carvão nas posições longitudinais e radiais estudadas; o rendimento em líquido pirolenhoso e gases não condensáveis apresentaram variações nas temperaturas de 700°C e 800°C; a variação do rendimento gravimétrico em carvão, entre as temperaturas de 500°C a 900°C foi de 15%; a variação do rendimento em líquido pirolenhoso no sentido radial de amostragem foi, em média, de 8%; a variação do rendimento em gases não condensáveis no sentido radial de amostragem foi, em média, de 16%.