The use of thermochemical pretreatment to enhance the anaerobic biodegradability of sugarcane bagasse

Abstract

This study aimed to evaluate the effect of physical and thermochemical pretreatments on the sugarcane bagasse biodegradability. After milling, the sugarcane bagasse was pretreated with diluted-hydrochloric acid or sodium hydroxide, at temperature of 120°C. The parameters, reaction time and concentration of the alkali were evaluated for optimization of pre-treatments using a statistical experimental design. After pretreatment, anaerobic biodegradability tests were performed using the material hydrolysed by the set of parameters that presented the best removal efficiency of lignin (alkali pretreatment). The test was also carried out using the milled bagasse and the hydrolysed material after acid pretreatment. In these tests, an inoculum consisting of a mixture of several anaerobic sludges was used. The results showed that when the diluted-acid pretreatment was used, an efficiency of 63.2% of hydrolysis of the cellulosic material was found with 60min of reaction time and 1.3M hydrochloric acid. For the alkaline hydrolysis, 102min reaction and 0.32M NaOH was the best set of parameters for removal of lignin. Using these parameters, the bagasse biodegradability increased from 61% to 64% using the alkali pretreatment, whereas it decreased to 52% using acid pretreatment. However, pretreatment can be useful for systems operated at lower retention time, i.e. eight days.