1. INTRODUCTION AND OBJECTIVES

Caracterização energética das madeiras de clones de Eucalyptus cul-tivados em diferentes localidades

The use of forest biomass or its derived charcoal as firewood can generate environmental and economic advantages for the Brazilian energy matrix. In this context, the main objective was to evaluate the energy potential of certain eucalyptus genetic materials, which are used by the charcoal production sector. We have evaluated six materials of Eucalyptus ssp. at the age of seven years from commercial plantations, spaced 3 x 3m, grown in the Alto Vale do Jequitinhonha, in Minas Gerais. Based on the production data, the average annual increment and the physical and chemical analyzes of the wood and the charcoal produced with it, we have estimated parameters to compare the potential of each genetic material, such as mass and energy of wood and charcoal per hectare, as well as the energy density. The results show that a material of Eucalyptus urophylla has greater energetic potential in relation to the others because it presents higher energy/ hectare estimated for its wood and consequently for charcoal produced with it. However, a material of Eucalyptus cloeziana presented a higher energetic density of the wood and its charcoal, showing advantages mainly in the transport.

Pyrolysis is a promising technology for thermal conversion of lignocellulosic biomasses into a higher added value fuel. The aim of this study was to analyze the potential of four agroforestry biomasses to produce energy as a raw material or as a bio-coal. In this study, slow pyrolysis was conducted in three final temperatures to evaluate the bio-coal production of four agroforestry biomasses widely available in Brazil. The biomasses used were sugarcane bagasse (Saccharum sp.), bamboo (Dendrocalamus giganteus), straw bean (Phaseolus vulgaris) and eucalypts wood chips (Eucalyptus sp.). In the first part was presented the raw biomasses proprieties, such as lignin, carbon, hydrogen and ash contents. In the second part was showed the bio-coal proprieties, such as gravimetric and fixed carbon yields, fixed carbon and ash contents. These bio-coal results were showed as a function of final temperature of pyrolysis. The best energy indicators for bio-coal production, such as fixed carbon yield, high heating value, was observed in the bamboo and eucalypts. The bagasse and straw bean biomasses have high concentrations of ash and low lignin content when compared with the other biomasses assessed and are less suitable to produce bio-coal.

Caracterização do carvão vegetal produzido em fornos retangulares industriais - DOI:10.5039/agraria.v14i3a5659

The objective of this work was to evaluate the drying speed of Eucalyptus urophylla logs in high temperatures and the influence of the presence or absence of bark and also the diameter of the log in the drying rate. Eucalyptus logs 60 cm long were divided into three diameter classes: 8-12 cm; 12,1-16 cm and 16,1-20 cm. The logs were dried in a heater with forced air circulation, in the presence or absence of bark in five temperatures: 50, 75, 100, 125 and 150ºC. The mass and the initial moisture were determined from each log and the water loss was kept up with periodic weightings, closing the drying process when the logs reached 20% moisture. The drying rate of the logs was calculated using the ratio between the total loss of moisture and the time in hours in order to reach the established moisture. It was concluded that the increase in temperature promotes the raise of the drying ratio, as being higher for smaller logs in relation to bigger ones and in addition to this, the bark effect was not significant in the drying of eucalyptus logs above 100ºC. It was also concluded that the best conditions for the operation of artificial dryers for Eucalyptus logs containing bark and separated in diameter classes would be at 125ºC.