Thermal decomposition of oil-palm solid wastes, including oil-palm shell, fibre and kernel, was studied by thermogravimetric analysis (TGA). Effect of heating rate and sample particle size on the behaviour of thermogram and kinetic parameters were investigated. The one-step global model, two-step consecutive model and two-parallel reactions model were used to simulate the pyrolysis process of the three materials studied. The one-step global model was able to describe the fractional weight loss upon pyrolysis of oil-palm kernel reasonably well but gave a large deviation for oil-palm shell and fibre. The two-step consecutive model could improve the fitting for oil-palm shell and fibre, but it cannot account for the inflection characteristic of the thermogram. Prediction by the two-parallel reactions model gave the best fitting with the experimental data of all oil-palm wastes under all pyrolysis conditions investigated. This proposed model was also tested with other biomass materials and proved to be satisfactory. (c) 2007 Elsevier Ltd. All rights reserved.