The aim of this work was investigate the kinetics of the thermal decomposition reaction of sugarcane straw. The thermal decomposition experiments were conducted at four heating rates (1.25, 2.5, 5 and 10°C/min) in a thermogravimetric analyzer using nitrogen as inert atmosphere. The kinetic analysis was carried out applying the isoconversional method of Friedman, and the activation energies obtained varied from 154.1kJ/mol to 177.8kJ/mol. The reaction model was determined through master plots, corresponding to a two-dimensional diffusion. The pre-exponential factor of 1.82*10(9)s(-1) was determined by linearization of the conversion rate equation as a function of the inverse of absolute temperature, concerning to activation energy of 149.7kJ/mol, which are in the order of magnitude for biomass thermal decomposition reported in literature. Finally, the theoretical and experimental conversion data showed a very good agreement, indicating that these results could be used for future process modeling involving sugarcane straw.

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Coffee husk, a major lignocellulosic waste derived from the coffee industry, was first ground into flour of fine particles of approximately 90 µm and then torrefied at 250 °C to make it more thermally stable and compatible with biopolymers. The resultant torrefied coffee husk flour (TCHF) was thereafter melt-compounded with polylactide (PLA) in contents from 20 to 50 wt% and the extruded green composite pellets were shaped by injection molding into pieces and characterized. Although the incorporation of TCHF reduced the ductility and toughness of PLA, filler contents of 20 wt% successfully yielded pieces with balanced mechanical properties in both tensile and flexural conditions and improved hardness. Contents of up to 30 wt% of TCHF also induced a nucleating effect that favored the formation of crystals of PLA, whereas the thermal degradation of the biopolyester was delayed by more than 7 °C. Furthermore, the PLA/TCHF pieces showed higher thermomechanical resistance and their softening point increased up to nearly 60 °C. Therefore, highly sustainable pieces were developed through the valorization of large amounts of coffee waste subjected to torrefaction. In the Circular Bioeconomy framework, these novel green composites can be used in the design of compostable rigid packaging and food contact disposables.

This work aims the study of the drying (25 ± 3 °C-150 °C) and thermal decomposition (150-900 °C) of sugarcane straw kinetics in inert and oxidative atmospheres by nonisothermal thermogravimetry (TG) analysis using heating rates of 2.5, 5 and 10 °C/min. The drying kinetic analysis was carried out using five models, Lewis, Page, Henderson and Pabis, Midilli and Logaritmic, obtaining the activation energy of 1.25 kJ/mol, in which the Page's model showed to be the most accurate description for both atmospheres. The thermal decomposition kinetics was analyzed through three consecutive reactions scheme, obtaining activation energies of 130, 200 and 56 kJ/mol as well as 200, 350 and 100 kJ/mol for both atmospheres, respectively. The consecutive reaction scheme allowed an excellent agreement between experimental and modeled data, providing a quality of fit similar than the obtained with independent parallel reactions scheme.