Comparative study on the thermal behavior of untreated and various torrefied bark, stem wood, and stump of Norway spruce

•Comparative study on the thermal behavior of torrefied bark, stem wood and stump.•Thermal stability of the samples is interpreted in terms of the chemical composition changes.•The residence time has larger effect at higher torrefaction temperature.•Hemicellulose side groups are split at milder torrefaction conditions compared to the galactomannan chain.•Principal component analysis has been used to identify statistical correlations.