Integrate marine plastics from the coast into urban recycling?

Some scientists have analyzed the possibility of incorporating marine litter from the coast into the urban solid waste management system of towns with a coast or very close to the sea, which would allow its subsequent recycling.

The study is the work of researchers from the University of the Basque Country (UPV/EHU).

In response to the millions of tonnes of marine litter, mostly plastic, floating in the oceans, the need to manage this waste effectively is more urgent than ever. Faced with this reality, the Materials + Technologies research group at the University of the Basque Country has proposed taking a first step.

“We have evaluated a practical approach: the possibility of integrating plastics collected at sea into the urban waste system. This pioneering study, which is part of a doctoral thesis, explores the possibility of managing this waste efficiently in current urban recycling infrastructures,” explains Cristina Peña, professor in the Department of Chemical and Environmental Engineering at the School of Engineering. from Gipuzkoa (UPV/EHU) and co-author of the work.

Unlike municipal solid waste, marine waste does not yet have a systematic management system; This is done very punctually and within the framework of very specific projects. “It is important to keep in mind that this waste, having been in the sea, presents a significant level of degradation different from that of, for example, a bottle placed in a yellow container under normal conditions. Therefore, our starting point and key question was precisely this: does the level of degradation that marine waste presents prevent its classification in an urban waste management process?” says Amaia Mendoza, researcher in the Materials + Technologies research group. from the UPV/EHU.

“In this work,” adds Amaia Mendoza, “we use identical PET water bottles from the same brand to evaluate the effects of different environmental conditions. We divided the bottles into two batches: we left the first one outdoors for nine months, simulating its exposure on a beach or rocky coast, and we submerged the second batch in the sea for the same period. “We observed that submerged bottles experienced greater chemical degradation, while those exposed to open air on the ‘coast’ remained in better condition.” This approach has allowed them to analyze how the degradation process varies depending on marine conditions and how each type of waste responds in different environments.

Next, “we simulated how these materials would be managed in an urban solid waste treatment plant,” to see if the automatic separation equipment in these plants would be able to identify and separate plastic bottles of marine origin. “To find out, we conducted tests with an optical separation system, a type of technology that automatically classifies materials according to their composition,” and observed that the separation effectiveness of bottles of marine origin—both those exposed to the open air and those submerged in the sea—“were very high, comparable to that of urban waste bottles,” comments Amaia Mendoza. “These results indicate that the treatment of marine bottles in these plants is viable and could be implemented successfully. The state of degradation is essential to determine the viability of its subsequent recycling,” the UPV/EHU researchers emphasize.

From left to right: Amaia Mendoza, Galder Kortaberria and Cristina Peña, from the research team. (Photo: UPV/EHU)

According to these researchers, “the study has achieved important progress by demonstrating that it is possible to separate PET bottles of marine and urban origin in a joint process, which marks a first step in an area with enormous development potential.” Likewise, “it opens the way to explore the automatic separation of other plastics present in marine waste, such as polypropylene or polyethylene, in urban waste treatment plants,” adds Amaia Mendoza.

The team from the University of the Basque Country highlights that the objective of this work has been to evaluate the possibility of revaluing marine waste by making it attractive as usable raw material. “If we manage to find practical applications and encourage the industrial development of these materials, their collection will also be attractive. The more efficient and viable the management of this waste is, the greater the incentive will be to take advantage of it and, consequently, increase interest in collecting it from the sea,” says Cristina Peña.

This study is based on the doctoral thesis of Amaia Mendoza Larrañaga who is part of the Materials + Technologies research group of the Department of Chemical and Environmental Engineering at the School of Engineering of Gipuzkoa (UPV/EHU). The thesis was prepared under the direction of Cristina Peña Rodriguez and Oihane Cabezas Basurko. Cristina Peña Rodríguez is a professor at the Department of Chemical and Environmental Engineering and director of the University-Business-Society Classroom at the School of Engineering of Gipuzkoa.

The study is titled “Industrial optical sorting for marine plastic litter management”. And it has been published in the academic journal Waste Management Bulletin. (Source: UPV/EHU)