Granulometric Characterization and Alteration during Composting of Industrial Cork Residue for Use as a Growing Medium

Abstract

This work describes the granulometry of industrial cork residue (bark of Quercus suber L.) and its possible alteration during composting to eliminate the high content of phytotoxic substances. Because of the differences in density of the different-sized cork particles, expression of the granulometric distribution in relation to volume reflected the size distribution more accurately than its expression in relation to weight. As a consequence, predictions of the physical and hydrological behavior of the substrate, deduced from its granulometry, were more accurate when this was calculated in relation to volume. Objective parameters used for textural comparison, such as the geometric mean (dg) and standard deviation of particle size (σg), which were previously used in soils, were tested. These permit the estimation of small differences in the particle size of different lots or the granulometric alteration occurring during composting. With the same purpose, a new diagram of textures for the classification of granular substrates was also studied.