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Plastics as Feedstocks for a Circular Economy: PET Flows and Recycling Processes
Citation:
Smith, Raymond L. Plastics as Feedstocks for a Circular Economy: PET Flows and Recycling Processes. American Chemical Society, Spring Meeting, Indianapolis, IN, March 26 - 30, 2023.
Impact/Purpose:
This abstract describes a presentation for the American Chemical Society, for the Spring Meeting to be held in March of 2023. The presentation is on research that supports Sustainable Materials Management in EPA’s Office of Resource Conservation and Recovery. Municipal Solid Waste (MSW) is a postconsumer use stream where some plastics are recycled. This effort determines current flows of plastics through Material Recovery Facilities (MRF), recycling “reclaimer” processes, and conversion into products, with the example case study of polyethylene terephthalate (PET, plastic #1). The analysis points to where postconsumer plastic ends up. What fraction is recycled? What products are recycled? And into what products does recycled PET end up? Information about these flowrates and the associated resource use and releases to the environment supports efforts in Sustainable Materials Management, where individual generation, recycling, composting, combustion with energy recovery, and landfilling flows are tracked within the non-hazardous waste management hierarchy.
Description:
As chemists and engineers look to be more sustainable in their use, reuse, and recycling of materials, plastics are playing an ever-increasing role in the U.S. economy. U.S. inflation-adjusted manufacturing shrunk for the last 10 years (0.5% per year), while manufacturing of plastics grew at 0.7% per year [1]. In addition to economics, sustainability also considers a social pillar, where plastics offer societal benefits with prospects for future advances and at the same time concerns from accumulation in landfills, habitats, and wildlife, and then exposure to humans, as well as leaching of chemicals from plastics [2]. In this effort the focus is on the environmental aspects of sustainability, in particular recycling of plastics and their resource use and environmental releases. The aspiration towards a circular economy for plastics forecasts that plastic recycling could increase in this growing part of the economy and that chemists and engineers could be interested in the prospects of this feedstock. Plastic recycling can only happen if systems are in place and used. Thus, these system limitations represent barriers to increasing plastic recycling, which this effort studies along with the processes involved and the flows of plastics through the system. Throughputs for material recovery facilities (MRFs) are modeled as input-output flows and then processed downstream at reclaimers, where plastics are prepared for final reuse. Polyethylene terephthalate (PET) is of particular interest because it is the most widely recycled plastic in the U.S. PET finds use in plastic bottles, thermoforms for food packaging, carpeting, and textiles, but only bottles are commonly recycled. As postconsumer PET flows through MRFs and reclaimer recycling processes, resource use and environmental releases are estimated, along with recycled flowrates and purities which describe the PET recycling system. Finally, recycled PET is converted into new products such as fibers, films, and bottles. This recycling system provides an example of a circular economy which, while only partially manifested due to limitations on collection, processing, and conversion of recycled PET, offers direction on how materials can be maintained in the economy and the associated processes considered for sustainability [3]. [1] Plastics Industry Association (2022). 2022 Size and Impact Report, Executive Summary. Washington, DC. https://www.plasticsindustry.org/sizeandimpact [2] Thompson, R.C., C.J. Moore, F.S. von Saal, S.H. Swan (2009). “Plastics, the environment and human health: current consensus and future trends,” Phil. Trans. R. Soc. B, 364, 2153-2166. https://royalsocietypublishing.org/doi/10.1098/rstb.2009.0053 [3] Smith, R.L., Takkellapati, S., and Riegerix, R.C. (2022), “Recycling of Plastics in the United States: Plastics Material Flows and Polyethylene Terephthalate Recycling Processes,” ACS Sustain. Chem. Eng., 10, 2084-2096. https://pubs.acs.org/doi/10.1021/acssuschemeng.1c06845 The views expressed in this presentation are those of the author and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency.