Upgrade the torrefaction process of bamboo based on autohydrolysis pretreatment

Abstract Torrefaction is a routine and effective method for recovering energy from biomass. In this study, autohydrolysis pretreatment was proposed to upgrade the torrefaction process of moso bamboo, and their relationship was evaluated. Results showed that about 80.24 % of bamboo hemicellulose were dissolved during autohydrolysis pretreatment. Compared with main chain, arabinan side chain of hemicellulose was much easier to be degraded, and more uniform hemicellulose could be obtained at 160 °C. The O/C values of autohydrolysis solid residues and the mass yield of torrefied bamboo decreased gradually with the enhancement of reaction severity (autohydrolysis and/or torrefaction), while the HHV values increased. The higher torrefaction temperature or autohydrolysis pretreatment severity was, the better thermostability of torrefied bamboo could be observed. 2D-HSQC of milled wood lignin revealed that autohydrolysis pretreatment can effectively accelerate the degradation of β-O-4 linkage in lignin and increase G-type lignin content during torrefaction process. Compared with direct torrefaction, prehydrolysis can greatly facilitate the torrefaction process and enhance the quality of final products.