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- All Subjects: Plastics
- Creators: Akula, kapil Chandra
- Creators: Allenby, Braden R.
Description
Polypropylene, a non-biodegradable plastic with a higher c-c bond disassociation energy than other conventional polymers like Polyethylene (PE), is used to manufacture these three-layered masks. The amount of plastic pollution in the environment has grown tremendously, nearing million tons in a short period of time. As a result, the purpose of this study is to reduce the environmental damage caused by facemasks. This M.S. thesis offers a concise overview of various thermochemical methods employed to depolymerize plastic waste materials. It emphasizes environmentally conscious and sustainable practices, specifically focusing on solvothermal processing. This innovative approach aims to convert discarded face masks into valuable resources, including hydrocarbons suitable for jet fuel and other useful products.
The thesis provides an in-depth exploration of experimental investigations into solvothermal liquefaction techniques. Operating under specific conditions, namely, a temperature of 350°C and a reaction duration of 90 minutes, the results were notably impressive. These results included an exceptional conversion rate of 99.8%, an oil yield of 39.3%, and higher heating values (HHV) of 46.81 MJ/kg for the generated oil samples. It's worth noting that the HHV of the oil samples obtained through the solvothermal liquefaction (STL) method, at 46.82 MJ/kg, surpasses the HHV of gasoline, which stands at 43.4 MJ/kg.
The significant role of the solvent in the depolymerization process involves the dissolution and dispersion of the feedstock through solvation. This reduces the required thermal cracking temperature by enhancing mass and thermal energy transfer. While solvolysis reactions between the solvent and feedstock are limited in thermal liquefaction, the primary depolymerization process follows thermal cracking. This involves the random scission of polypropylene (PP) molecules during heat treatment, with minimal polymerization, cyclization, and radical recombination reactions occurring through free radical mechanisms.
Overall, this work demonstrates the feasibility of a highly promising technique for the effective chemical upcycling of polypropylene-based plastics into valuable resources, particularly in the context of jet fuel hydrocarbons, showcasing the comprehensive analytical methods employed to characterize the products of this innovative process.
ContributorsAkula, kapil Chandra (Author) / Deng, Shuguang (Thesis advisor) / Fini, Elham (Committee member) / Salifu, Emmanuel (Committee member) / Arizona State University (Publisher)
Created2023
Description
Plastic is a valuable part of the consumer economy, but it creates negative environmental externalities throughout its lifecycle. To reduce these effects, a sustainable circular economy is needed, where more plastic is diverted from landfill or environmental sinks through reduction, reuse, recycling, or composting, while addressing social needs. Although many different stakeholders (industry, academia, policymakers) are calling for a sustainable circular economy for plastics, globally, less than 20% of plastic is recycled with no data on reduction and reuse. In this dissertation, a mixed methods approach is used to suggest how organizations related to the plastic industry can implement a sustainable circular economy. The first chapter identifies how firms across the plastic value chain can innovate to adopt a sustainable circular flow. A systematic review reveals over 300 examples, which are used to create a material flow typology. Findings summarize five critical points of innovation and indicate that innovation adoption is low. More concerted efforts are needed to improve innovation adoption and there is a need to shift innovation focus from resource efficiency to sustainability. The second chapters studies U.S. plastic recyclers’ price signals to generate evidence for favorable recycling policies. A hedonic analysis reveals recyclers preferences for recyclability – plastic properties that enable recycling. Results suggest that adequate recycling infrastructure and absence of virgin plastic can play an important role in facilitating more recycling. In the third paper, the role of governments as consumers is studied. As the largest consumers in a market, governments can signal a large demand for circular products and services, however public administration literature has paid limited attention to it. A theoretical framework is created to fill the knowledge gap and suggest how governments can use sustainable public procurement for a circular economy. A systematic literature review of the top ten public administration journals over 32 years reveals critical knowledge gaps and the potential for important sustainable public procurement research
ContributorsHafsa, Fatima (Author) / Englin, Jeffrey (Thesis advisor) / Abbott, Joshua K (Committee member) / Darnall, Nicole (Committee member) / Dooley, Kevin J (Committee member) / Arizona State University (Publisher)
Created2022
Description
Fossil resources have enabled the development of the plastic industry in the last century. More recently biopolymers have been making gains in the global plastics market. Biopolymers are plastics derived from plants, primarily corn, which can function very similarly to fossil based plastics. One difference between some of the dominant biopolymers, namely polylactic acid and thermoplastic starch, and the most common fossil-based plastics is the feature of compostability. This means that biopolymers represent not only a shift from petroleum and natural gas to agricultural resources but also that these plastics have potentially different impacts resulting from alternative disposal routes. The current end of life material flows are not well understood since waste streams vary widely based on regional availability of end of life treatments and the role that decision making has on waste identification and disposal.
This dissertation is focused on highlighting the importance of end of life on the life-cycle of biopolymers, identifying how compostable biopolymer products are entering waste streams, improving collection and waste processing, and quantifying the impacts that result from the disposal of biopolymers. Biopolymers, while somewhat available to residential consumers, are primarily being used by various food service organizations trying to achieve a variety of goals such as zero waste, green advertising, and providing more consumer options. While compostable biopolymers may be able to help reduce wastes to landfill they do result in environmental tradeoffs associated with agriculture during the production phase. Biopolymers may improve the management for compostable waste streams by enabling streamlined services and reducing non-compostable fossil-based plastic contamination. The concerns about incomplete degradation of biopolymers in composting facilities may be ameliorated using alkaline amendments sourced from waste streams of other industries. While recycling still yields major benefits for traditional resins, bio-based equivalents may provide addition benefits and compostable biopolymers offer benefits with regards to global warming and fossil fuel depletion. The research presented here represents two published studies, two studies which have been accepted for publication, and a life-cycle assessment that will be submitted for publication.
This dissertation is focused on highlighting the importance of end of life on the life-cycle of biopolymers, identifying how compostable biopolymer products are entering waste streams, improving collection and waste processing, and quantifying the impacts that result from the disposal of biopolymers. Biopolymers, while somewhat available to residential consumers, are primarily being used by various food service organizations trying to achieve a variety of goals such as zero waste, green advertising, and providing more consumer options. While compostable biopolymers may be able to help reduce wastes to landfill they do result in environmental tradeoffs associated with agriculture during the production phase. Biopolymers may improve the management for compostable waste streams by enabling streamlined services and reducing non-compostable fossil-based plastic contamination. The concerns about incomplete degradation of biopolymers in composting facilities may be ameliorated using alkaline amendments sourced from waste streams of other industries. While recycling still yields major benefits for traditional resins, bio-based equivalents may provide addition benefits and compostable biopolymers offer benefits with regards to global warming and fossil fuel depletion. The research presented here represents two published studies, two studies which have been accepted for publication, and a life-cycle assessment that will be submitted for publication.
ContributorsHottle, Troy A (Author) / Landis, Amy E. (Thesis advisor) / Allenby, Braden R. (Thesis advisor) / Bilec, Melissa M (Committee member) / Arizona State University (Publisher)
Created2015