Isothermal thermogravimetric measurements were performed on recycled cellulosic materials. The kinetic parameters were determined with the Avrami-Erofe＇ev equation from two different ways. The first one consists of the determination of n from the slope of the variations of In(-ln(1-alpha)) versus ln(t) and apparent activation energy Delta E from the slope of ln(k(T)) versus 1/T. The second one also gives the values of n and Delta E from a numerical fit of the experimental data. Both methods lead to the same results and show that the reaction order of the degradation process of the cellulose is close to unity. The value of this reaction order allows the interpretation of the dynamic thermogravimetry data with the Broido method. Using this method on a series of recycled cellulose with different content of chemical and mechanical paper pulps, we show that the apparent activation energies depend linearly onto paper pulp ratio.