Optimization of sugarcane bagasse autohydrolysis for methane production from hemicellulose hydrolyzates in a biorefinery concept.

Abstract

This study aimed to optimize through design of experiments, the process variables (temperature – T, time – t and solid-to-liquid ratio – SLR) for sugarcane bagasse (SB) autohydrolysis (AH) to obtain hemicellulose hydrolyzates (HH) prone to anaerobic digestion (AD) and biochemical methane production (BMP). The results indicated that severe AH conditions, which lead to maximum hemicelluloses dissolution and sugar content in the HH, were not the best for BMP, probably due to the accumulation of toxic/recalcitrant compounds (furans and lignin). Mild AH conditions (170 _C, 35 min and SLR = 0.33) led to the highest BMP (0.79 Nm3 kg TOC_1), which was confirmed by the desirability tool. HH produced by AH carried out at the desired condition DC2 (178.6 _C, 43.6 min and SLR = 0.24) showed the lowest accumulation of inhibitory compounds and volatile fatty acids (VFA) and highest BMP (1.56 Nm3 kg TOC_1). The modified Gompertz model best fit the experimental data and led to a maximum methane production rate (R) of 2.6 mmol CH4 d_1 in the best condition.