In this work, thermogravimetric analysis is carried out on four different biomass samples such as bagasse, coir–pith, groundnut shell and casuarina leaves to study their thermal behaviour. Analysis is put through in an inert nitrogen atmosphere from ambient temperature to 800°C at a heating rate of 10°C/min. Three reaction zones corresponding to dehydration, hemicellulose–cellulose degradation and lignin degradation are observed for all four biomass samples. The kinetic parameters such as activation energy, pre–exponential factor and order of the reaction for all the components of samples are determined using the simple Arrhenius equation. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 256–266, 2014