AVALIAÇÃO DO PRÉ-TRATAMENTO ALCALINO DA PALHA DE CANA-DE-AÇÚCAR VISANDO SEU APROVEITAMENTO PARA PRODUÇÃO DE ETANOL

Abstract

In order to reduce the intense dependence on oil, renewable alternatives are being increasingly studied to obtain second generation ethanol. Ethanol is commonly obtained by fermentation from sugarcane juice in autonomous distilleries attached to Brazil, but it can be produced by converting fermentable sugars from lignocellulosic biomass such as straw and sugarcane bagasse. sugar cane. Straw has grown gradually due to environmental factors that promoted laws prohibiting the burning of this material and, with the surplus in the field, it represents a new byproduct for obtaining second generation ethanol. The carbohydrates constituting this residue need to be solubilized by pretreatment processes, making the structure more susceptible to enzymatic hydrolysis, aiming at the release of sugar monomers that can be fermented and distilled for ethanol production. Thus, the present work aimed to promote alkaline pretreatment of sugarcane straw aiming the production of second generation ethanol. Thus, a linear experimental design 23 was performed, with 3 central points and 8 unique combinations, totaling 11 trials. The factors analyzed were: NaOH concentration (0.25 M, 0.5 M and 0.75 M), temperature (60, 80 and 100 °C) and time (20, 40 and 60 min). Assay 8 (0.75M, 60 min and 100 ° C) presented the best performance among the others, as it indicated the highest concentration of reducing sugars (2.42 g / L), lowest yield (55.40%) and highest solubilization of macromolecular components (44.60%). In addition, pretreatment has also been shown to be effective in removing lignin from the residue. According to the analysis of the effect estimates for reducing sugars released after the pretreatment step, performed using the Statistica software, the temperature (X3) was statistically significant at the 95% confidence level. Infrared spectroscopy analysis showed that pretreatment promoted structural changes in the residue under study. The obtained results show the advantage of alkaline pretreatment in the solubilization process of the straw macromolecular components, presenting itself as a low cost alternative for second generation ethanol production processes