The delamination of metalized multilayer flexible packaging using a microperforation technique

Multilayer flexible packaging waste is a critical issue in the field of waste management as it is considered a non-recyclable material. One of the solutions to increase its recyclability is the delamination, which allows the recycling of the different polymer layers separately. This study investigated the optimization of the delamination by microperforating this plastic. The diffusion model was described by Fick's first law. The delamination process was tested at three different temperatures (50, 65 and 80 °C) with caustic soda. In addition, the influence of other parameters such as the thickness of aluminium layer, the presence of inks and the use of surfactants was tested. As a result, the microperforation technique improved the delamination rate by decreasing the residence time by 83% at the optimum conditions studied, being the thickness of the metal and the temperature essential factors affecting the process. However, the presence of inks and surfactant had no effect.Support for this work was granted by PID2019-105359RB-I00 project from the Ministry of Science and Innovation of Spain

Plastics recycling: new challenges in the age of the circular economy

El sector de los plásticos está experimentando un importante cambio de dirección hacia la sostenibilidad y la innovación. El modelo de Economía Circular como alternativa al modelo tradicional de producción, uso y vertido está generando un gran impacto en nuestra sociedad. La recuperación y reciclaje de materiales se ha convertido en una etapa importante dentro del sector y se prevé que la demanda de productos reciclados aumente en los próximos años. Sin embargo, el sector del reciclaje no está preparado para cumplir la creciente demanda, sobre todo, en cuanto a la calidad de los materiales. En esta tesis se han estudiado los métodos de tratamiento de residuos plásticos desde tres puntos de vista: medioambiental, tecnológico y calidad del producto final. Se ha dedicado un capítulo de la tesis para profundizar en cada uno de estos temas. Para estudiar el impacto medioambiental se ha realizado un análisis de ciclo de vida comparativo entre un proceso de reciclaje innovador alineado con los principios de la Economía Circular y dos métodos de tratamiento de residuos tradicionales. Desde el punto de vista tecnológico, se ha estudiado el proceso de eliminación de agua durante el reciclaje de plásticos flexibles con el objetivo de optimizar parámetros y reducir el consumo de energía. Por último, se llevado a cabo un estudio de las sustancias orgánicas semivolátiles presentes en plásticos reciclados, ya que éstas pueden suponer un riesgo para la salud de los consumidores si se utilizan en aplicaciones de alto valor añadido. Además, se ha realizado un estudio exhaustivo del estado del arte de los sistemas de gestión de residuos plásticos, prestando especial atención a los plásticos flexibles debido a que su tasa de reciclaje se encuentra por debajo de los plásticos rígidos. Como resultado se han identificado los puntos débiles y se han marcado directrices para impulsar la transición hacia la Economía Circular

Plastic flexible films waste management – A state of art review

Plastic flexible films are increasingly used in many applications due to their lightness and versatility. In 2014, the amount of plastic films represented 34% of total plastic packaging produced in UK. The flexible film waste generation rises according to the increase in number of applications. Currently, in developed countries, about 50% of plastics in domestic waste are films. Moreover, about 615,000 tonnes of agricultural flexible waste are generated in the EU every year. A review of plastic films recycling has been conducted in order to detect the shortcomings and establish guidelines for future research. This paper reviews plastic films waste management technologies from two different sources: post-industrial and post-consumer. Clean and homogeneous post-industrial waste is recycled through closed-loop or open-loop mechanical processes. The main differences between these methods are the quality and the application of the recycled materials. Further research should be focused on closing the loops to obtain the highest environmental benefits of recycling. This could be accomplished through minimizing the material degradation during mechanical processes. Regarding post-consumer waste, flexible films from agricultural and packaging sectors have been assessed. The agricultural films and commercial and industrial flexible packaging are recycled through open-loop mechanical recycling due to existing selective waste collection routes. Nevertheless, the contamination from the use phase adversely affects the quality of recycled plastics. Therefore, upgrading of current washing lines is required. On the other hand, household flexible packaging shows the lowest recycling rates mainly because of inefficient sorting technologies. Delamination and compatibilization methods should be further developed to ensure the recycling of multilayer films. Finally, Life Cycle Assessment (LCA) studies on waste management have been reviewed. A lack of thorough LCA on plastic films waste management systems was identified.This work was supported with a Grant from the University of Alicante as part of the InnoUA Transfer of Knowledge programme (Industrial Doctorate)

Centrifugal dewatering performance in plastic films recycling

Dewatering of plastic films is a highly energy-consuming recycling operation that largely affects the quality of the recycled product. Despite the importance of good drying, this operation has not been studied at laboratory or pilot plant scale. In this work, the mechanical dewatering of blown film grade high density polyethylene has been assessed by using a laboratory centrifuge. It is suggested that a plastic cake is formed under the centrifugal forces similar to the sludge cake after the filtration process. The water is retained within the plastic cake due to three phenomena: free water within the cake pores and voids, water maintained by capillarity (superficial and pendular) and water trapped due to the tortuosity of the plastic mass. The total moisture is a sum of an equilibrium moisture and a transient moisture. The equilibrium moisture depends on the centrifugal force (G) but it is independent of time. Conversely, the transient moisture is reliant on both the G-force and the centrifugation time. The experimental results showed that an optimum side length exists. The moisture content is minimized when the flake side lies between 1 and 2 cm. Finally, it has been found that the moisture content is a function of the plastic surface. Hence, the specific moisture content (the mass of water per total plastic surface) should be calculated to compare films with uneven thickness or made of different materials. In sum, the outcomes of this study may be fundamental for the further and more extensive research into the plastic films dewatering processes.This work was supported with a Grant from the University of Alicante as part of the InnoUA Transfer of Knowledge programme (Industrial Doctorate)

Non-intentionally added substances (NIAS) in recycled plastics

The demand for high quality recycled polymers in the European plastic industry is on the increase, likely due to the EU’s Plastic Strategy intended to implement the circular economy model in this sector. The problem is that there is not enough recycled plastic in the market. In terms of volume, post-consumer plastic waste could be key to meet the current and future demand. Nevertheless, a high level of contamination originated during the product’s life cycle restricts its use. The first step to change this must be identifying the undesired substances in post-consumer plastics and performing an effective risk assessment. The acquired knowledge will be fundamental for the development of innovative decontamination technologies. In this study, 134 substances including volatile and semi-volatile compounds have been identified in recycled LDPE and HDPE from domestic waste. Headspace and solvent extraction followed by GC/MS were used. The possible origin of each substance was studied. The main groups were additives, polymer and additives breakdown products, and contamination from external sources. The results suggest that recycled LDPE contains a broader number of additives and their degradation products. Some of them may cause safety concerns if reused in higher added value applications. Regarding recycled HDPE, the contaminants from the use phase are predominant creating problems such as intense odors. To reduce the number of undesired substances, it is proposed to narrow the variety of additives used in plastic manufacturing and to opt for separate waste collection systems to prevent cross-contamination with organic waste.This work was supported by a grant from the University of Alicante as part of the InnoUA Transfer of Knowledge program and cofinanced by Cadel Deinking (Industrial Doctorate)

Analysis of plastic waste circularity through LCA

Upcycling processes are better aligned with the Circular Economy model, which defends that the plastic waste is a valuable resource with the potential to be recirculated in a new material cycle. To ensure the highest number of cycles, products, components and material should be kept at their highest utility and value (Webster, 2017). However, this is not what is happening in the recycling sector because upcycling processes are more complex, and energy and resource-intensive. As a result, the environmental benefits of plastic upcycling are frequently called into question and downcycling methods are implemented owing to their lower complexity and costs, regardless of the irreversible and meaningful loss of quality. In this work, three plastic waste management scenarios have been assessed to determine their potential to contribute to the implementation of the Circular Economy. The chosen waste treatment methods are upcycling of plastic scrap through deinking technology, downcycling by re-extrusion and, finally, incineration. The environmental impacts have been computed through LCA methodology. The results show that depending on the assumptions made, LCA can lead to conclusions which are opposite to the Circular Economy principles, thus favouring the downcycling and incineration of plastic waste with high potential to be recirculated. Therefore, to make a fairer comparison between upcycling and other waste treatment options, two modifications have been suggested. First, the target market for recycled pellets should be included in the computation since it is reliant on the material´s quality. Downcycled dark pellets can be used in applications which cover 24% of the total market. Conversely, upcycled pellets can reach 100% of the market. And second, the energy produced during incineration cannot substitute the energy from fossil fuels. The heating value of plastics is usually higher than the energy consumed during raw pellets production. Therefore, recycling will be always seen as the least favourable option. Nevertheless, according to the Circular Economy principles, the energy has to come from renewable sources. Therefore, if our society is moving forward to this new model, fossil fuels should not be considered. Finally, it has been demonstrated that increasing the quality of recycled plastics through upcycling processes is more beneficial than increasing the recycling rates. This is to say that recycle more is good, but what is needed is to recycle better. This work is aligned with two of the conference topics: LCA of municipal and industrial waste management scenarios. LCA of the management of specific waste streams in a circular economy perspective. Reference: Webster, K., 2017. The circular economy: A wealth of flows. Ellen MacArthur Foundation Publishin

Upcycling of printed plastic films: LCA analysis and effects on the circular economy

In this work, the environmental impacts caused by an innovative upcycling process of printed plastic scrap have been assessed through Life Cycle Analysis (LCA) methodology for the first time. The process consists of removing the inks from the plastic surface before extrusion, so that clear high quality pellets are obtained, suitable to be used in high added value applications (such as packaging). The upcycling technology is compared with two traditional waste treatments: conventional recycling (or downcycling) and incineration with energy recovery. Upcycling is considered to be better aligned with Circular Economy principles and its implementation in the industry requires a comprehensive analysis of environmental impacts. Despite the importance of this topic, only a few studies can be found in the literature. Furthermore, the lack of uniformity and consensus in LCA modelling can lead to the conclusion that upcycling causes the biggest environmental burdens. Therefore, downcycling or incineration are shown as preferable options, regardless of the irreversible loss of the plastics’ potential to be recirculated. To avoid this error, we have emphasised the importance of including the market share for recycled products in the LCA modelling and establishing the virgin plastic substitution ratio correctly. Also, we have suggested that in the perspective of the Circular Economy, the energy produced during incineration cannot substitute the energy from fossil fuels.This work was supported with a Grant from the University of Alicante cofunded by Olax22 as part of the InnoUA Transfer of Knowledge programme (Industrial Doctorate UAIND2016-04). The author O. Horodytska kindly wishes to thank the University of Alicante for a pre-doctoral employee stays grant UAEEBB2018-04, which has been used to develop the research at École Polytechnique Fédérale de Lausanne (EPFL); and the ICT4SM group for their support during the research stay