The thermal degradation of kenaf (Hibiscus cannabinus) under the effect of several variables (particle size, Ar flow rate, sample initial mass and heating rate) was investigated. From experimental data and by application of various model-free methods (Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa), the activation energies (EA) were calculated as a function of conversion. The results obtained allowed to conclude that kenaf follows a multi-stage degradation mechanism, with EA values ranging 170-225 kJ mol-1. Despite the slight differences showed by the three methods on the EA values, they agreed about the pattern of EA with conversion.