Biofuels and their blends with fossil fuel are important energy resources, whose production and application have
been largely increased internationally. This study focuses on the evaluation of the activation energy of the thermal
decomposition of three pure fuels: farnesane (renewable diesel from sugar cane), biodiesel and fossil diesel and their
blends (20% farnesene and 80% of fossil diesel — 20F80D and 20% farnesane, 50% fossil diesel and 30% biodiesel —
20F50D30B). Activation energy has been determined from thermogravimetry and Model-Free Kinetics. Results
showed that not only the cetane number is important to understand the behavior of the fuels regarding ignition
delay, but also the profile of the activation energy versus conversion curves shows that the chemical reactions are
responsible for the performance at the beginning of the process. In addition, activation energy seemed to be suitable
in describing reactivity in the case of blends of renewable and fossil fuels