Jatropha curcas seed cake is a viable feedstock for co-firing with coal as it has the advantages of being renewable, carbon-neutral and sourced from a versatile plant. Torrefaction, a mild pyrolysis treatment by heating in a N-2 atmosphere, was investigated as a technique to improve the thermochemical properties of the biomass, primarily the HHV (higher heating value). The temperature and holding time were varied in the ranges of 200-300 degrees C and 0-60 min, respectively, to form a 5-level full-factorial experimental matrix. An optimum envelope of torrefaction parameters was identified in the range of <5 min at >280 degrees C to >45 min at 220-250 degrees C under a heating rate of 10 degrees C/min. This results in an enhancement of the HHV from 24 MJ/kg to more than 27 MJ/kg, which is within the range of coal, while maintaining an energy yield higher than 90%. The relationships between the HHV and "the proximate fixed carbon content as well as the elemental CHO content were also investigated. Through C-13 NMR (nuclear magnetic resonance) spectroscopy, hemicellulose was determined as the most volatile component, undergoing decomposition before 250 degrees C while cellulose only degraded fully in the 250-300 degrees C range and lignin decomposition spanned from 200 degrees C to beyond 300 degrees C. (c) 2016 Elsevier Ltd. All rights reserved.