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With the objective of evaluating the correlation of wood basic density with age in seven Eucalyptus grandis clones planted in Brazil, five trees in each clone were sampled at the ages of 0, 5, 1, 5, 2, 5, 3, 5, 4, 5 and 7, 5 years. The analysis of these samples showed that the intraclonal variation of the basic density (except for 0, 5 year-old) was very low, while the interclonal variation was moderately high (from 7, 5 % at 0, 5 year-old to 4, 1 % at 7, 5 year old) for all ages. The analysis of variance indicated that the variation between clones, between ages and the clone ( age interaction were all significant (P < 0, 01), but the variation of the basic density of the trees within-clones were non-significant. The study of temporal stability of the basic density showed that most of the clones behave similarly to the mean clone for all ages. According to the analysis of regression of the mean basic density per clone using temporal-index as predictor it was found that for this group of clones is it possible to predict the basic density of wood produced at one age from its value at another age. Indeed, the correlation of the basic density at different ages within a clone showed that, except for the correlations for wood of 0, 5 year-old, all other correlations were statistically significant. However, it can be noted that correlations based on more recent ages presented higher values of coefficient of correlation, even if the same time span has been considered. Also, it was shown that was it possible to estimate the basic density using the age of the tree as independent variable through the logarithmic model both for individual clones (R2 from 75 % to 96 %) and for all seven clones analysed together (R2 = 92 %). Southern African Forestry Journal No.191 2001: 21-28

Objetivou-se, nesse trabalho, avaliar os briquetes dos resíduos do processamento dos grãos de café submetidos aos processos de carbonização e torrefação. Os briquetes foram carbonizados utilizando-se taxa de aquecimento de 1,67 ºC min-1 com temperatura inicial de 50 ºC e final de 450 ºC, por 30 min. A torrefação dos briquetes foi realizada em uma mufla em duas taxas de aquecimento: 1,5 e 3,0 ºC min-1 até 250 ºC, temperatura mantida durante 60 min. Foram determinados os rendimentos em briquetes torrificados e carbonizados, em líquido pirolenhoso, em gases não condensáveis e em carbono fixo. Para todos os briquetes foram quantificados os teores de carbono fixo, cinzas, voláteis, dos componentes elementares (C, H, N, S, O), o poder calorífico superior, a densidade aparente e energética e a resistência à compressão diametral. Os briquetes carbonizados apresentaram maior potencial energético devido aos elevados teores de carbono fixo e elementar e poder calorífico, porém baixa resistência mecânica. Os briquetes torrificados nas duas taxas de aquecimento consideradas apresentaram características e propriedades energéticas semelhantes mas densidade energética inferior em relação aos briquetes carbonizados e in natura. This research aimed to evaluate the briquettes made with residues from processing of coffee grain submitted to carbonization and torrefaction. The briquettes were carbonized at a heating rate of 1.67 ºC min-1 with initial temperature of 50 ºC and final of 450 ºC, which was kept during 30 min. The torrefaction of the briquettes was made in a muffle furnace at two heating rates: 1.5 and 3.0 ºC min-1 until 250 ºC, temperature kept during 60 min. The yields in torrefied and carbonized briquettes, pyroligneous liquor, non-condensable gases and fixed carbon were determined. For all briquettes the fixed carbon, ash, volatile and elemental components (C, H, N, S, O) contents and higher heating value, apparent and energetic density and resistance to diametric compression were quantified. The carbonized briquette presented high energetic potential due to higher fixed and elemental carbon content and heating value, but had low mechanical resistance. The briquettes torrified at the two considered heating rates presented similar energetic properties and characteristics, but lower energetic density than carbonized and fresh briquettes.

The addition of alkaline and high-cation exchange capacity (CEC) biochars is a suitable strategy to increase the CEC of weathered soils. The aim of this study was to evaluate the effect of biochar from different feedstocks and pyrolysis temperatures on the CEC of two contrasting Oxisols. Biochars produced from chicken manure (CM), eucalyptus sawdust (ES), coffee husk (CH) and sugarcane bagasse (SB),plus a control (without biochar), at 350, 450, and 750 &deg, C were mixed with the soils at 2, 5, 10 and 20% (w/w) and incubated for 9 months. Feedstock, pyrolysis temperature and addition rate of biochar were key factors controlling the alteration of soil CEC. The CH biochar pyrolyzed at 350 &deg, C was the most effective matrix at increasing soil CEC. In a rate-dependent way, ES and SB biochars increased C contents of both soils without improving soil CEC. The efficiency of high-ash biochars in enhancing soil CEC in both Oxisols was limited by the alkalization caused by high rates of CH and CM biochars. The increase in CEC is soil-dependent and modulated by high-ash biochar CEC and application rate, as well as by the original soil CEC.