Identification of significant factors in the consumption of expanded polystyrene by Zophobas atratus larvae through an experimental Placket-Burman design

Abstract

Expanded polystyrene (EPS) is a widely used polymer with a poor recycling rate; this has led to several environmental problems. New treatments such as the use of larvae to digest EPS have been proposed. Nevertheless, few studies have been carried out to identify the culture conditions and environmental factors that might affect this process. The influence of 5 continuous (temperature, humidity, water % in diet, plastic particle size and larvae density) and 2 categorical (presence of oat and larvae size) factors on EPS consumption by Zophobas atratus larvae was studied through a Plackett-Burman screening design. Response variables were a) survival rate and b) Specific degradation efficiency (EED). Digested EPS was analyzed by Fourier transformed infrared spectroscopy (FTIR) to determine possible structural modifications. Temperature and relative humidity had the higher significance influence (P<0.05) on EED. For the survival rate, the most significant factors were temperature (P<0.05), presence of oat (P<0.1) and plastic particle size (P<0.1). FTIR analyses showed formation of new O-H and C-O functional groups and a decrease in C-H substituents in the aromatic ring of the EPS, suggesting probable biodegradation of the material.