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1. Optimization methods for plastics management supply chain design

   https://doi.org/10.1002/aic.18464  

   Wang, Shuheng; Maravelias, Christos_T (May 2024, AIChE Journal)

   Abstract This article introduces three mixed integer programming (MIP) models to address a network design problem for mixed plastic waste (MPW) supply chains. By tracking waste compositions throughout the supply chain, the models optimize the technologies needed to process MPW. The three models adopt different approaches to preserve composition information in the supply chain. We also remark on how to improve solution times with additional constraints, and how the models can be easily modified to handle larger‐scale problems. The proposed models provide an approach for examining emerging MPW recycling technologies that may be more sensitive to input composition, as well as determining the extent to which advanced sorting is useful. 

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2. A System-Dynamics Based Approach for Modeling Circular Economy Networks: Application to the Polyethylene Terephthalate (PET) Supply Chain

   https://doi.org/10.69997/sct.107833  

   Pert, Daniel; Torres, Ana Ins (July 2025, PSE press)

   The transition to a circular economy (CE) requires agents in circular supply chain (SC) networks to take a variety of different initiatives, many of which are dynamic in nature. We use a system dynamics (SD)-based approach to develop a generic framework for dynamic modeling of CE networks and propose a prototypical circular SC network by combining dynamic models for five actors: a manufacturer, consumer, material recovery facility (MRF), recycling facility, and the Earth. We apply this framework to the supply chain for Polyethylene Terephthalate (PET) plastic packaging by considering different scenarios over a 65-year time horizon in the US. We include both slow-down-the-loop initiatives (i.e., those that extend product use time through demand reduction or reuse) and close-the-loop initiatives (i.e., those that reintroduce product to the supply chain through recycling) by the consumer, as well as sorting and recycling capacity expansion. We find that, given the current recycling infrastructure in the U.S., slow-down-the-loop initiatives are more effective than close-the-loop initiatives for improving circularity and minimizing environmental impact. However, combining the two initiatives eliminates the need for capacity expansion and leads to the highest circularity in the shortest amount of time. 

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3. Enzyme Discovery and Engineering for Sustainable Plastic Recycling

   Baotong Zhu, Dong Wang (March 2021, Trends in biotechnology)

   null (Ed.)

   The drastically increasing amount of plastic waste is causing an environmental crisis that requires innovative technologies for recycling post-consumer plastics to achieve waste valorization while meeting environmental quality goals. Biocatalytic depolymerization mediated by enzymes has emerged as an efficient and sustainable alternative for plastic treatment and recycling. A variety of plastic-degrading enzymes have been discovered from microbial sources. Meanwhile, protein engineering has been exploited to modify and optimize plastic-degrading enzymes. This review highlights the recent trends and up-to-date advances in mining novel plastic-degrading enzymes through state-of-the-art omics-based techniques and improving the enzyme catalytic efficiency and stability via various protein engineering strategies. Future research prospects and challenges are also discussed. 

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4. Enzyme Discovery and Engineering for Sustainable Plastic Recycling

   Baotong Zhu, Dong Wang (March 2021, Trends in biotechnology)

   null (Ed.)

   The drastically increasing amount of plastic waste is causing an environmental crisis that requires innovative technologies for recycling post-consumer plastics to achieve waste valorization while meeting environmental quality goals. Biocatalytic depolymerization mediated by enzymes has emerged as an efficient and sustainable alternative for plastic treatment and recycling. A variety of plastic-degrading enzymes have been discovered from microbial sources. Meanwhile, protein engineering has been exploited to modify and optimize plastic-degrading enzymes. This review highlights the recent trends and up-to-date advances in mining novel plastic-degrading enzymes through state-of-the-art omics-based techniques and improving the enzyme catalytic efficiency and stability via various protein engineering strategies. Future research prospects and challenges are also discussed. 

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5. Recycled Polymers As a Feedstock for Chemical Manufacturing Supply Chains in the United States: A Network Analysis for Polyethylene Pyrolysis

   https://doi.org/10.1021/acssuschemeng.3c00990  

   Chen, Zhichao; Kimura, Yosuke; Allen, David T. (June 2023, ACS Sustainable Chemistry & Engineering)

   For chemical recycling of plastic wastes to be viable, chemical products generated in recycling need to find markets. A network model of the U.S. chemical manufacturing industry was used to assess at what cost points, and the extent to which, chemical products from thermal pyrolysis of polyethylene might find markets in the current U.S. chemical manufacturing industry. Network modeling determined the cost points at which the simulated industry network utilized the thermal pyrolysis products and which processes were displaced by the supply of recycled materials. The characteristic feature of the simulations is the large number of processes in the chemical manufacturing network that are impacted by the availability of a relatively small number of products from polyethylene recycling. In the case of polyethylene recycling, the capital cost requirements for expanding capacity to effectively utilize the recycled materials is greater than the capital required for the pyrolysis process. This suggests that identifying scenarios where recycled materials can be utilized in processes that have excess capacity will be a critical consideration in techno-economic analyses of recycling plastics. 

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