Biodegradable material vs non-degradable materials: s consumption of compostable plastics less harmful than oil-derived plastics?

Given the harmful impact of plastics on organisms’ fitness, one question arises: is compostable material (derived from non-oil sources) any better? Here we assessed the fitness effects of consuming two oil-derived plastics (polyethylene and polystyrene) and one compostable product in insects, utilizing Tenebrio molitor beetles as the study system. Animals were fed during the larval stage either of four different treatments: a) polyethylene + apple/wheat; b) polystyrene + apple/wheat; c) compostable product + apple/wheat; and d) apple/wheat alone. Upon reaching the adult stage, insects were provided with wheat and apple for 7 days, allowed to mate, and lay eggs. We recorded developmental rate and mortality from larvae to pupa, weight and fecundity, and survival probability from one stage to the next. Mortality was higher when animals consumed any type of plastic. The probability of survival was also affected, particularly in the pupal and adult stages. Feeding with any type of plastic oil-derived or compostable plastic led to a reduction in body size and reproductive success (measured as surviving larvae). Notably, in some cases, the group fed with compostable plastic was the most affected. Delays in development at different stages could increase mortality, while the decrease in egg production in females and the reduction in adult size could imply carry-over effects on demography. Perhaps, the additional materials in compostable products imply toxic effects like those caused by plastics. Thus, the effects of compostable products are not any better than those of plastics.