Optimization of expanded polystyrene biodegradation by Zophobas atratus larvae

Abstract

Expanded polystyrene foam (EPS) is a recyclable polymer. However, high energy consumption and the use of chemicals in the process make this alternative non-optimal. Biodegradation of EPS by insect larvae is considered an ecological way to eliminate plastic waste. This report focused on optimizing the consumption of EPS by Zophobas Atratus larvae, for this, a Box-Behnken respond-surface design was developed considering three factors: a) temperature b) relative humidity (HR%) and c) particle size of plastic (PSP). Specific rate of degradation (SRD) and survival rate of the larvae were evaluated as response variables. Temperature and HR% had significant direct effects on survival rate (P<0.5). As for the SRD, all three factors had significant direct effects (P<0.05) as well as the interaction temperature-PSP (P<0.01). A significant quadratic effect (P<0.05) of temperature was also observed. The max theoretical values of SRD (5.37 mg EPS larvae-1 day-1) were obtained under the following culture conditions: T=27.42°C, HR%=54.24 and PSP=0.50 in3. This statistical optimization proved to be a viable experimental procedure to increase EPS consumption by Z. atratus larvae.