Study on the physical properties of alternative growing media to LECA: Growing media composite made from HDPE/rice husk/calcium carbonate

Abstract

Three categories of composite from the mixtures of high-density polyethylene (HDPE), calcium carbonate and rice husk were produced as an alternative growing media. Category A (HDPE/calcium carbonate), Category B (HDPE/rice husk) and Category C (HDPE/calcium carbonate/rice husk) composites were prepared using Brabender Measuring Mixer at 50 rpm and 180 °C. In this study, physical properties (bulk density, porosity, water absorption and pH) of each category were investigated and compared to commercial growing media, light expanded clay aggregate (LECA). Field Emission Scanning Microscope (FeSEM) was also used to determine the pore sizes and pore distribution of the media produced. The result showed that porosity and water absorption of media increased with increasing percentage (w/w) of rice husk while bulk density increased with increasing percentage of calcium carbonate. pH of media made from HDPE/calcium carbonate is higher (basic) compared to those made from HDPE/rice husk (slight acidic). FeSEM revealed all media are porous but pore sizes greatly affected media porosity and water absorption capability. From the result, it can be concluded that the specific composition of media composite produced (C3 and C6) has comparable physical properties with LECA and could be used as an alternative growing media.