Análise energética da madeira e do carvão de híbridos entre Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson e Corymbia torelliana (F. Muell.) K.D. Hill & L.A.S. Johnson

This research aimed to evaluate the wood and charcoal quality of hybrids clone of the crossing C. citriodora with C. torelliana in two different locations for charcoal production. Seven with 3,75 years old clones, planted at country of Itamarandiba – MG, and six 6,42 years old clones, planted in Dionísio – MG, were studied. For wood and charcoal quality analysis, samples were collected along the stem of the trees until the commercial height. Properties study of the wood was done by chemical analysis, basic density, superior heat power, and thermogravimetric analysis. The wood samples were carbonized in laboratory conditions with heating rate of 1.67 0 C.min -1 , starting at 100 0 C until 450 0 C and keeping on this temperature for 30 minutes. It were determined the carbonizations gravimetric yield, all in dry basis. The wood quality was evaluated based on the chemical immediate analysis, relative apparent density, and gross heating value. The experiment was installed according to the completely randomized design, with five repetitions. The collected data were submitted to analysis of variance and, when the evaluated effects were significant by “F” test, was applied the Scott-Knott test at 5% probability for multiple comparisons. For correlation analysis, Pearson correlation coefficient, tested by the "t" test at 5% probability was used. Results showed variability of wood between the genetic materials evaluated in relation to place and plant crossing. The thermal analysis of the wood showed significant variation between clones and it was possible to differentiate two stages of degradation (hemicelluloses and cellulose). The majority of the clones presented satisfactory properties for the charcoal production, while, clone 3, planted in Itamarandiba, obtained the best performance due it have the higher yield and energetic efficiency, thus, achieving the best potential for charcoal production. However, clone 9, planted in Dionísio, was the less indicated for charcoal production since it presented the lowest energetic efficiency, gravimetric yield, and densities.

Determinação da densidade amostral ótima para a geração de mapas temáticos na cafeicultura de precisão

Among the crops commercially exploited in Brazil, the coffee has a great economic importance, especially in the states of Minas Gerais and Espirito Santo. In the search for higher yield and lower environmental impact, farmers and researchers seek to develop new technologies that result in greater efficiency in various production processes of the coffee. For this, the adoption of precision agriculture in the management of operations in coffee crops, called precision coffee, has shown results that justify its use, by identifying the spatial variability of several variables, allowing its localized management and in the proper intensity. Unlike conventional management that is based on the average of observations in an area, precision agriculture uses a more detailed sampling, based on a sampling grid, which allows to represent in greater detail the reality of farming. Many previous studies have identified the spatial variability of the production of coffee system variables, but without worrying about the quality of information obtained due to the sampling grid used as precision and accuracy. Given the above, the objective of this study was to evaluate the quality of four different sampling grids for different variables and three times, in order to identify the most appropriate grid for use in precision coffee. Also aimed to compare the results between the precision coffee and conventional, according to reference values.

Utilização do óleo extraído dos resíduos da filetagem de tilápia (Oreochromis niloticus) para produção de biodiesel

The aims of this study were to evaluate the potential of the oil extracted from tilapia residues filleting for biodiesel production, select the one that presents the greatest potential for this purpose and characterize the obtained biodiesel to be neutralized or refined and analyzed according to their physicochemical and yield characteristics. For this, the crude heads, carcasses and offal which have undergone physical and chemical analysis and yield were extracted. For this, the crude oil was extracted from the heads, carcasses and guts, which have passed through physicochemical and yield analysis.For the statistical analysis, a completely randomized design was used with 3 treatments (head, carcass and viscera) and 5 replications.It was observed significant differences in the oils (P <0.05) being the viscera oil the one that showed higher yield although it presented the worst values for all evaluated indices. For this reason this oil was selected for further studies. In this new stage of the study the treatments were: neutralized crude oil and viscera refined oil with different volumes of NaOH 16%.It was adopted a completely randomized design, with a 2x3 factorial (types of oil x soda volumes) with 3 replications. The analyzed variables were acid value, saponification index, peroxide value and iodine value. It was also evaluated the performance of all the obtained biodiesel. It can be concluded that: among the filleting residues oil of tilapias, the one which is more suitable for biodiesel production, due to its high yield, was the viscera oil. The use of all stages of refining is indispensable, once the obtained index and the yield were greater in the biodiesel refined oil; the produced biodiesel from tilapia’s viscera oil meets the ANP standards and, therefore, it is adequate for use.