Consumption of expanded polystyrene by Tenebrio molitor and Zophobas atratus, and use of their meal as feed for Piaractus brachypomus

Abstract

Expanded polystyrene (PS) provides a great challenge for environmental management due to its high levels of production and insufficient waste management. However, recent studies have demonstrated the capacity of Tenebrio molitor and Zophobas atratus to biodegrade PS, as well as the possibility of using the meal of these species to feed fish. The objective of this study was to evaluate the productive performance of the larvae of T. molitor and Z. atratus fed with varying levels of PS and evaluate the effect of the level of inclusion of the meal of these insects as a substitute for fish meal in the diet of Piaractus brachypomus fingerlings. In one experiment, the effect of 5 different levels of PS and wheat bran (WB) was evaluated (100% PS:0% WB, 75% PS:25% WB, 50% PS:50% WB, 25% PS:75% WB, and 0% PS:100% WB) on growth and composition of T. molitor and Z. atratus larvae. In a second experiment, 10 different diets for Piaractus brachypomus fingerlings were evaluated involving five levels (100, 75, 50, 25, and 0%) of substitution of the fish meal of a conventional dietary formulation with meal of T. molitor or Z. atratus previously fed with PS. In the first experiment, the best treatment for both species was 25% PS:75% WB, resulting in the highest growth rate and consumption of PS. In the second experiment, no significant differences were found among treatments for any of the variables evaluated for productive performance for the fish. We conclude that up to 100% of the fish meal in the diet of Piaractus brachypomus fingerlings may be replaced with meal of T. molitor or Z. atratus fed with PS, although there is a need for further studies regarding the long term health effects on the fish and the humans that consume them.