Spouted bed technology is suitable for the thermal treatment of biomass by combustion (San José et al., 2002) and by pyrolysis (Aguado et al., 2000, 2002; Olazar et al., 2001). Therefore, it would be adequate for the thermal treatment of mixtures of biomass wastes with non appreciable segregation, due to the ability to handle granular and fibrous materials and mixtures of different sizes and textures with the low segregation because of the cyclic movement of solid particles (San José et al., 1994). In previous paper (San José et al., 2009) the hydrodynamics of beds consisting of biomass mixtures wastes of different characteristics in spouted beds of different geometry (contactor angle and gas inlet diameter) and in different operating conditions (stagnant bed height, particle diameter and gas velocity) have been studied. In this paper, the segregation of binary mixtures of biomass wastes of different size and shape has been quantified. The operation has been carried out in a pilot plant scale experimental unit operating with conical contactors of different geometry, at gas velocities over the minimum spouting velocity (10% and 20% over the minimum spouting velocity). The biomass wastes used have been sawdust, shaving and wood chips, of density s= 560 kg/m3, of Sauter mean diameter = 1.5, 1.9, 2.5 and 3.1 mm. In order to quantify the segregation, solid sampling, at different bed levels in the bed, has been carried out by means of a probe connected to a suction pump, provides of a computer-coordinates displacement device. The segregation has been quantified by using the mixing index calculated from the experimental values of weight fraction of particles of greater effective diameter in the upper volume half of the bed, and the weight fraction in the whole bed, (San José et al., 1994). In the Figure, the weight fraction of the particles of greater effective diameter, XH, against the bed level has been plotted as an example of the results for a mixture corresponding to bed consisting of 50 wt % of binary mixture of sawdust and shaving of Sauter mean diameter = 1.9 mm, = 36º; Do= 0.04 m; Ho= 0.24 m). It is observed that the component of bigger size is in greater proportion in the upper part of the bed. ACKNOWLEDGMENTS This work was carried out with the financial support of the University and of the County Council of Biscay (Project DIPE 07/09) REFERENCES Aguado, R., Olazar, M., San José, M.J., Aguirre, G., Bilbao, J. Ind. Eng. Chem. Res., 39, 1925-1933(2000). Aguado, R., Olazar, M., San José, M.J., Gaisan, B., Bilbao, J. Energ. Fuel, 16(6) 1429-1437(2002). Olazar, M., Aguado, R., San Jose, M.J, Bilbao J. J. Chem. Technol. Biotechnol., 76(5), 469-476(2001). San José, M.J., Olazar, M., Peñas, F.J., Bilbao, J. Ind. Eng. Chem. Res., 33, 1838-1844(1994). San José, M.J., Aguado, R., Alvarez, S., Olazar, M. Inf. Tecnol., 13(2), 127-131(2002a). San José, M.J., Alvarez, S., López, L.B., García, I. Clean Technology, 109-112(2009).