Transitions of thermogravimetric signals beneficial for formation of the binder-less briquetted biofuel of pigeon pea crop residues were investigated. Thermal hardening or softening of the different components of bio-material in briquetted biofuel was explained in terms of transitions of thermogravimetric signals and activation energy levels. The activation energy profiles with respect to conversion fraction for raw residue and its briquette was studied by Kissinger-Akahira-Sunose method. The activation energy profile of briquette showed dominancy over raw residues of pigeon pea crop highlighting the overall hardening in briquetted biofuel. (C) 2014 Elsevier Ltd. All rights reserved.