Different variables affect the processes of compacting biomass, and these variables depend on the raw material, such as the type of wood or type of biomass being compacted, its moisture, size, as well as on other aspects relating to the manufacturing process, such as the pressure applied and the temperature reached during compaction. This work analyses the influence of the size of the sawdust particles from the bark of the species Pinus caribaea var. Morelet, which ranges from 0.63 to 2 mm; it had a moisture content in dry basis of 6; 9.5; 13 and 20%; and the force applied in the laboratory was 8000, 12,000, 16,000 and 20,000 N. These values are relatively high given that they do not take into account the heat caused by the matrixes chafing with the material to be compacted, as occurs in industrial processes. The different experimental treatments were processed and statistically analysed using SSPS version 12.0, and Statgraphics version 5.0. Once the data had been tested in the ANOVA and in various comparison tests, it was observed that the results did not show any significant differences between the pellets obtained with forces of 16,000 and 20,000 N, or between pellets obtained with 9.5 and 13% moisture, and that the pellets with higher qualities were obtained from particle sizes of between 1 and 2 mm. (C) 2009 Elsevier Ltd. All rights reserved.