Plastic clean-up mechanisms: Experimental insights on their bycatch

Plastic clean-up technologies are mechanical interventions designed to remove existing plastic litter, which can contribute to improved water and environmental quality. Even though organic materials and organisms may be unintentionally caught, the current lack of data hinders the evaluation of their actual impact. The goal of this work was to experimentally assess the proportion of bycatch during the operation of two non-commercial and custom-made clean-up mechanisms: floating booms coupled with a wheel and catch units, and a curtain of air bubbles with a catch unit. Our results show that both clean-up mechanisms were non-selective and generally caught plastic items and biota items (referring here to plant-derived materials) with median proportions of bycatch ranging from 18.4% to 95.0% depending on the parameters and clean-up mechanism. For example, with an increasing number of plastic items, an increase in the proportion of bycatch was observed for the floating booms coupled with a wheel and catch units. We observed a median of 25.0% bycatch with no plastic to a median value of 35.9% during the interaction of biota items with 100 plastic items. For the curtain of air bubbles and a catch unit, no trend was observed on proportion of reed caught with an increasing number of plastic items. Data on plastic clean-up technologies are needed to guarantee their net benefits while ensuring minimal environmental impact, and good water ecological status.