The pyrolytic and kinetic characteristics of two macro-algae (Laminaria japonica and Sargassum pallidum) and sodium alginate were evaluated and compared at heating rates of 10.30 and 50 degrees C min(-1) under an inert atmosphere after which the kinetic factors were calculated. The results indicated that three stages appeared during pyrolysis, moisture evaporation, primary devolatilization and residual decomposition Significant differences in the average activation energy, thermal stability, final residuals and reaction rates existed between the samples studied. The primary devolatilization stage of L. japonica and S dum could be described by the Avramic-Erofeev equation (n = 3), whereas that of alginate sodium could be described by the Jander equation (n = 2). Calculation of the most probable mechanism function of zone I of the two macro-algae indicated that alginate was mainly decomposed during zone I The average activation energies of L japonica, S. pallidum and sodium alginate were 207.7, 202 9 and 188.1 kJ mol(-1) respectively (C) 2010 Elsevier Ltd. All rights reserved