Bamboo (Phyllostachys sulphurea (Carr.) A. et C. Riv.) was torrefied at temperatures ranging from 280 to 340 degrees C and holding times between 10 and 90 min. The changes of mass yield, high heating value, and energy yield were investigated. The variations of the chemical components were depicted in Ross diagram and the alterations of H/C and O/C were plotted in van Krevelen diagram. The structural changes of the torrefied bamboo were studied by Fourier transform infrared and nuclear magnetic resonance spectroscopies and the morphology was examined by scanning electron microscopy. Results indicated that a high temperature and long holding time produced the torrefied sample with low mass and energy yields. The lignin mass fraction increased due to the transformation of carbohydrate degradation products when the torrefaction severity increased. Only a minor amount of cellulose was detected (0.15%) when torrefied at 320 degrees C and a higher temperature of 340 degrees C resulted in the complete removal of carbohydrates. The torrefaction at 340 degrees C and holding time of 60 min produced solid products with H/C and O/C ratios lower than those of lignite. Less water and hydrogen bonding sites were presented in heavy torrefied bamboo resulted from the degradation of both cellulose and hemicelluloses. With the increase of temperature, aliphaticity decreased but aromaticity increased due to the deoxygenation and dehydration reactions. The mass fraction of absorbed moisture of bamboo decreased with the increase of torrefaction temperature and prolongation of holding time. (C) 2015 Elsevier Ltd. All rights reserved.