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.

Kinetic study of pyrolysis of castor beans (Ricinuscommunis L) presscake: an alternative use for solid waste arising from the biodiesel production

This work investigated the effects of temperature and of rate of heating on the kinetic parameters of pyrolysis of castor beans presscake, a byproduct generated in the biodiesel production process. Pyrolysis process was investigated by thermogravimetric analysis, and parameters were obtained from nonisothermal experiments. The results obtained from the process of thermal decomposition indicated the elimination of humidity and the decomposition of organic components of the biomass. DTG curves showed that the heating rate affects the temperature of maximum decomposition of the material. Kinetic parameters such as activation energy and pre-exponential factor were obtained by model-free methods proposed by Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Kissinger. Experimental results showed that the kinetic parameters values of the FWO and KAS methods display good agreement and can be used to understand the mechanism of degradation of the cake. In a generalized way, the results contribute to better understanding of the processes of biomass pyrolysis.