SUSTAINABLE PARTICLEBOARDS FROM RICE HUSK AND WASTE POLYSTYRENE ADHESIVE: A BIODEGRADABILITY STUDY

Abstract

Biodegradation is a biological process in which materials such as lignocellulosic biomass undergo decomposition through the action of microorganism, including bacteria, fungi, protozoa and others. This study investigates the biodegradability of rice husk particleboards (RHP) bonded with waste polystyrene adhesive using the Box-Behnken design. The optimal conditions found were pH 6.9, exposure time 11.5 weeks, and microbial broth volume 30.5 mL. Under these conditions, the cell mass reached 55.9 mg/L, and percentage biodegradation was 18.1%. This biodegradation level meets the NF U52–001 standard minimum requirement of 12% degradation after 2 months of soil burial. Experimental validation showed percentage errors of 0.98% for cell mass and 0.65% for biodegradation, both within the acceptable 10% error margin. Morphological analysis of decomposed rice husk identifiedAspergillus nigeras the dominant fungal species. SEM-EDX showed an increase in carbon concentration from 70.81% to 85.55% and nitrogen from 9.32% to 12.45% after biodegradation. This result appears counterintuitive as microbial decomposition usually reduces C and N due to mineralization. The observed increase likely results from the selective degradation of other elemental components, leading to a relative enrichment of carbon and nitrogen on the particleboard surface rather than an absolute increase. This suggests thatAspergillus nigerpreferentially degrades non-C and non-N elements or causes surface modifications that concentrate these elements. The Contois kinetic model best describes RHP biodegradation, with R 2 = 0.9647, a rate constant of 0.04530 wk −1 , and substrate affinity of 0.001667 g/L. Aspergillus nigershows modest potential for biodegrading rice husk particleboards bonded with synthetic adhesive under the investigated conditions.