Drying of dean olive stone (free of olive pulp) means a revaluation as biofuel especially used for thermal processes. This work has studied the time-dependent effective moisture diffusivity from isothermal drying experiments in a convective dryer. A new method, based on a modification of the simplified method, has been established to calculate this coefficient. A comparison between this method and the slope method has been carried out and similar results have been obtained. Modified simplified method requires fewer calculations than the slope method. The dependence between the effective moisture diffusivity, the temperature and the moisture ratio was analyzed by multiple regression analysis from a second order multivariate polynomial model and the mechanisms of moisture transport were exposed. Finally, the activation energy was analyzed and its values were shown with respect to the moisture ratio and the sample thickness. (C) 2015 Elsevier B.V. All rights reserved.