Análise temporal do preço do carvão vegetal oriundo de floresta nativa e de floresta plantada

Abstract

Wood charcoal is an energetic input mainly used in the pig- iron and steel production, as a term-reducer. It can be obtained from plantation forest or from native forest. These two types of charcoal possess some technical and economical characteristics that may differentiate their prices. This study analyzed the historical series of charcoal prices of both planted and native forest, in the period from January 1999 to December 2004. For analyzing the time series, models of time series were used, in order to find models able of supplying better forecasts and able of verifying if there are tendency differences and seasonality among the studied series. The choice of the most appropriate model for explaining the time series of charcoal was based on the graphical analyses, stochastic tests and criteria of evaluation of the order of the model. Among the adjusted models for charcoal prices of plantation forest, SARIMA (3,1,1)(3,1,0)12 provided better adjustment, while for the native forest prices, SARIMA (3,2,0)(3,1,0)12 provided better adjustment, demonstrating differences in the tendency among the two price series.