Investigation into the physical–chemical properties of chemically pretreated sugarcane bagasse

Enzymatic hydrolysis is one of the major steps involved in the conversion of sugarcane bagasse into ethanol. Pretreatments break down macrostructures in order to improve the enzyme access to the targeted glycosidic bonds. This study reports on the use of thermoanalytic techniques together with other different techniques for the verification of the structural and morphological changes occurred in sugarcane bagasse subjected to acid and alkaline pretreatments. The techniques evaluated differences in the BET and BJH surface areas, diameter and pore volume investigated by porosimetry, scanning electron microscopy and wettability. Thermal analysis (TG/DTG and DTA) was also used to evaluate the thermal degradation of hemicelluloses, cellulose and lignin contents that remained in the samples after pretreatments. The results show that chemical pretreatments were effective in the degradation of lignocellulosic samples and significant morphological changes occurred after the pretreatments. Acid and alkaline pretreatments caused an increase in the surface area, diameter and volume of pores. Wettability also revealed important effects regarding surface changes of the biomasses. In summary, all tested pretreatments were effective to chemically degrade the macrostructures of sugarcane bagasse that hinder enzymatic hydrolysis in, for instance, the second-generation ethanol production.