With high global ambitions for sustainability and circularity and increasing energy prices, the recycling industry keeps innovating to keep up with political goals and customer demand. Reducing the energy consumption in the recycling process reduces environmental impact and reduces financial costs for the customer. A energy intensive process step in recycling is oven drying the plastics to an acceptable moisture content. The energy cost can be reduced by using microwave irradiation as heat source. This research investigates the moisture content and the intrinsic viscosity (IV) of polyethylene terephthalate (PET) during and after the drying process. The measurements of the PET dried in an experimental setup employing microwave irradiation as heat source is compared to the drying process in a oven at 80, 100 and 150 ◦C. The IV of the virgin PET pellets did not decrease significantly after drying in the experimental setup, but it did decrease after drying in the oven at 150 ◦C. The moisture content decreases more rapidly in the oven at all temperatures than in the experimental setup. Scaling up the experimental setup should increase the drying rate. No indications of unfeasibility of microwave assisted drying are found. Keywords: PET (polyethylene terephthalate), Circular economy, Plastic recycling, Intrinsic viscosity (IV), Moisture content

Mountains of solid waste in landfills and rivers of plastic in oceans have become a symbol of modern society, more so in developing countries.

Asia is responsible for 71% of the world’s mismanaged plastics (Neo et al., 2021) with India ranking 12th in the world (Shanker et al., 2022). In contrast, several studies have determined that India has one of the world's highest plastic waste recycling rates, between 40-60% (Shanker et al., 2022). These two seemingly contradictory pictures make India, an interesting choice for a case study on plastic waste management in the developing context.

There are unrecognised warriors in the Global South who have been instrumental in achieving high plastic recycling rates. These are the informal waste workers who work outside the mainstream formal system and collect recyclable material from households, garbage dumps, or even landfills directly. In fact, India owes its successful plastic recycling rate in part to the informal sector.

While there have been studies to quantify the plastic waste management system of India, there is little known about the extent of the contribution of the informal sector to plastic recycling due to the ‘invisible’ nature of its operations.

This study attempts to expand the existing body of knowledge on the contribution of informal sectors in achieving high plastic waste recycling rates in India, by focusing on the test case of the city of Chennai in South India.

In that regard, this paper aims to address the following two sub-research questions related to the plastic recycling value chain: (1) What are the material flows of household plastic waste along the formal and informal recycling value chain of plastic waste in Chennai, and where do exchanges between the two sectors occur? (2) What are the data gaps in estimating the material flows, and the barriers and challenges in building a comprehensive MFA of plastic waste in the developing context?

To answer the first question, the tool Material Flow Analysis (MFA) is used to estimate the recycling value chain of plastic waste generated in Chennai. The plastic waste flows from the stage of waste generation in households to End-of-Life management are covered. The interplay between formal and informal waste sectors is included wherever present. To obtain data for the MFA model, secondary data from peer-reviewed literature, and other literature like reports, government publications, etc. are combined with primary data collected via field visits and interviews with experts.

Data unavailability is one of the biggest barriers to building a comprehensive MFA of plastic waste management system in Chennai, particularly the contribution of the informal sector. Thus, qualitative data obtained from the interviews about the barriers to data collection and the social issues that keep the system hidden from the outside is used to discuss the second research question. Finally, possible solutions to circumvent these issues are explored to promote the flow of information among internal and external stakeholders to envision a more effective and fair plastic waste management system.

The study highlights the importance of involving informal waste pickers in the plastic waste management process, as they play a significant role in achieving a circular economy through recycling plastic waste. By recognizing the contributions of the informal waste sector, this study also aims to improve the lives of waste pickers and promote their inclusion in the formal waste management sector.

The rare-earth elements (REEs) are Europe’s most critical raw-materials group due to the high supply dependency on the Chinese REEs near-monopoly. The NdFeB permanent magnet in EOL hard disk drivers (HDDs) is an actual source of REEs. However, REEs recycling routes are still under development. Hydrometallurgical routes are attractive because they are versatile, but concerns arise regarding their chemical consumption and the implication to the environment. An ex-ante environmental analysis supports the launch and consolidation of the route in an environmentally sound manner. This work aims to identify the environmental hotspots of a theoretical hydrometallurgical recycling route for REEs, which uses acetic acid for leaching and oxalic acid for precipitation. The route also allows chemical recycling through a loop within it. The ultimate goal is to draw recommendations toward improving the environmental profile of the technology before it gets implemented. The evaluation is carried using the Life Cycle Assessment (LCA) methodology according to a dedicated framework for ex-ante analysis, including upscaling. The analysis highlights as hotspots the oxalic acid in the precipitation stage and the direct dust emissions and its treatment in the fragmentation of HDDs. Moreover, results indicate that acetic acid regeneration within the system is more burdensome than use the chemical produced from raw materials. The premature assessment also indicates that the environmental profile of the emerging technology is potentially inferior to the established primary production. A limitation of the model arises from the economic allocation for multifunctional processes due to the approach developed to stipulate the price of some co-products. Overall, the uncertainties carried with the ex-ante LCA prevent any assertive declaration regarding the recycling route’s environmental performance. However, the exercise contributes to the problem-solution space. It gives directions to the next steps: better data collection for the RE recovery phase, less dust production in the fragmentation phase, other means for precipitation of REEs, and variation in the leaching solid-liquid ratio.

Functional gradients in hard-soft interfaces are abundant in nature, and we often mimic them to create strong and tough composites. A powerful tool for the designs and fabrication of biomimetic composites is voxel-based multi-material 3D printing. Earlier researches mainly focused on using this technique in the creation of gradients based on morphology. While this is a great way to create a gradient, the outcome material properties are often unknown. In this research, we attempted to create a gradient based on the desired outcome material properties rather than morphology. We created a linear gradient in density using a voxel-based 3D printing technique and tested it through nanoindentation. Furthermore, we created a Finite Element Model based on this sample. Out of the nanoindentation and Finite Element Model results, we extracted the b-value for a power-law function in the form of E(x)= E_h 〖ρ(x)〗^b+E_s. With the inverse of this power-law function, we designed three different gradients based on the desired material properties: a linear, stepwise, and sigmoid gradient. Nanoindentation experiments and Finite Element analyses showed that we achieved the desired outcome in material properties with our newly created approach of designing gradients. However, the nanoindentation experiments showed that using a machine suitable for the wide range of Young’s moduli present in these kinds of composites is crucial. To display the possible applications of our new approach, we designed a knee model with graded ligaments and tested it with a tensile test and digital image correlation. Results of these tests showed an energy before failure that was twice as high as its non-graded counterpart. Furthermore, with the introduction of the gradient, we achieved to change to loading condition on the ligaments. Overall, our results show that our new approach can create gradients based on material properties rather than morphology and opens many new doors in creating biomimetic composites.