Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 23 Issue 1

The recycling technologies fall into four groups of the recycling hierarchy (Singh et al., 2017; Vollmer et al., 2020) namely • Primary recycling (most intact) or closed-loop recycling refers to the recycling process where the material can be recycled to into products with similar properties, hence the plastic polymer is kept circulating in the same ‘loop’. Primary recycling takes place for pre- and post- consumer (mono- stream) plastics. This process of recycling can only happen when plastics are not mixed with other interfering materials or polymers. • Secondary recycling or open-loop recycling refers to the recycling process where the material can be recycled but the products are of lower quality than the virgin material, hence the latter are used as a lower value product and recycled in an ‘open-loop’. Currently, most consumer plastic recycling follows this route. The plastic waste contains a significant amount of contamination due to presence of other chemicals such as additives. • Tertiary recycling involves the conversion of plastic to feedstock and plastic to its initial monomer. In this case, the polymer is chemically modified, making sure that the valuable materials (feedstock, monomers) are being recovered. The polymer serves as a discarded material with the possibility of being converted into products such as syngas (H 2 /CO molar ratio of 2:1), waxes, diesel, new polymers. • Quaternary recycling (least intact) or incineration of plastic material with energy recovery. During its incineration, there is recovery of energy as heat and electricity. The amount of heat and power depend on the calorific value (energy content) of the polymer and the efficiency of the waste-to-energy plant. Primary recycling offers the best avenue for recycling (inner loop) whereas quaternary recycling (outer loop) the least (Singh et al., 2017). Nowadays, mechanical recycling plays the most important role in plastic recycling, and is categorized as secondary recycling (‘open-loop’ recycling) where the plastic is down cycled to be only partially re-used for the same purpose due to quality reduction (Ragaert et al., 2017; Sheppard et al., 2016). The quality and quantity recycling gaps is due to the collection of plastic waste in a mixed stream, having different polymers and even objects (metals, cardboard, rubber and so on). Furthermore, plastic products consist of about 30,000 chemicals, including multilayer material, copolymers, stickers, fillers and additives, which complicate the recycling process (Hopewell et al., 2009). However, there are alternative, innovative recycling technologies that address these shortcomings associated with the plastics from different waste streams. In particular, tertiary recycling allows plastic waste to be recycled to monomers or feed stocks with thermochemical methods (Vollmer et al., 2020). Chemical recycling options can also be considered; a process in volvingde polymerization where polymer bonds are broken through the use of chemicals, or dissolution with solvents while maintaining the polymer backbone (Vollmer et al., 2020). However, little is known in terms of the environmental impacts of these existing or innovative recycling technologies and consequently, it is difficult to determine which technologies are most appropriate in a circular economy. IV. L ife C ycle A ssessment (LCA) On the other hand, through Life Cycle Assessment or Life Cycle Analysis (LCA), the environmental impact of a product or technologies can be assessed over the course of its entire life. Life cycle management tools can contribute to the building up of a circular economy business model (Zinck et al., 2018 ; Avesani , 2020 ) . Application of LCA in the circular economy has been comprehensively described in literature (Kambanou and Sakao 2020).It is reported that the adoption of LCA can indeed contribute towards sustainable policy making and determine which technological innovations can provided the best solution to improve sustainable businesses. LCA also serves as a method to find the optimum product, service, or other solution, at some point in time and in regards to specific environmental effects, such as carbon emissions. Current LCA studies on plastic recycling are carried out to evaluate the positive environmental impact of a recycling technology against the present situation. The recycled polymers are termed as ‘avoided virgin polymer’ and are assigned a negative value as part of the environmental impact assessment, resulting in a ‘positive’ contribution (Gu et al., 2017). However, like any tool, it has its drawbacks where misleading or contradictory outcomes can be generated, therefore can not validate a circular economy model. The reason is that only a single recycling technology is taken into account, or only a specific waste stream (packaging or municipal plastic waste) (Chen et al., 2019; Gu et al., 2017). In addition, LCA studies can only be carried out with existing boundaries of waste stream on a short- term basis. System boundaries between polymers and recycling technologies involved in the LCA studies include polymer granulate production, recycling treatment impacts and avoided products. For a circular economy, systemic change needs to be considered which is on a long term basis. Other factors that should also be taken into account in these studies are product type, sector, and waste collection method. Thus, comparability cannot be achieved and eventually there is no possibility for scale up or to use the results in Holistic Approach to Tackle (Micro) Plastic Pollution: The Case of Mauritius 1 Year 2023 27 © 2023 Global Journals Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( H )