Identification of significant direct and interaction effects on expanded polystyrene degradation by zophobas atratus

Abstract

Expanded polystyrene (EPS) becomes a persistent waste and can remain in the environment for long periods of time. Recently, various species of insects with the ability to biodegrade EPS have been identified, some of them are even capable of mineralizing it. However, the influence of environmental factors on consumption rates (commonly low) have been scarcely evaluated. In the present study we used Zophobas atratus larvae in presence of EPS to determine the levels of statistical significance of 3 factors: a) relative humidity (%RH), b) temperature and c) % of water in the diet (%WD) on two responses: a) specific efficiency of degradation (EED) and b) survival rate through a complete factorial 23 design. All experiments were carried out for 25 days. %RH and temperature showed significant direct effects (P<0.01) on EED, and so did the interactions: Temperature – %RH and %RH - %WD (P<0.01). For the survival rate response, only the interaction Temperature - %WD showed significant influence (P<0.01). The highest EED (4.67mg EPS larvae-1 day-1) was observed at 32°C, 50% RH and 80% WD. This factorial analysis allowed us to improve our understanding of the magnitude and dynamic of environmental factors on EPS consumption rates by Z. atratus.