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An Analysis of Plastic Additive Fates from the Generic Chemical Processing of End-of-Life Plastics
Citation:
Chea, J., M. Conway, A. Lehr, P. Benavides, K. Yenkie, AND Gerardo J. Ruiz-Mercado. An Analysis of Plastic Additive Fates from the Generic Chemical Processing of End-of-Life Plastics. AIChE Annual Meeting 2023, Orlando, FL, November 05 - 10, 2023.
Impact/Purpose:
The end-of-life (EoL) stage of plastics and its infrastructure require further improvement to minimize energy consumption, prevent environmental releases of plastic additives, and avoid exposing humans and the environment to many hazardous substances. This conference presentation shows plastic recycling using chemical processing routes, material flow inventories, energy system analysis, and generic scenario analysis to track the fate of plastic additives through pyrolysis, gasification, and depolymerization. This work shows how these chemicals may further react with other chemicals during the chemical recycling process and generate unwanted side products that may interfere with the quality of the final product and increase environmental releases of hazardous materials. Internal and external stakeholders will be able to employ our findings in developing energy-efficient, safer, and more sustainable routes for the chemical recycling of plastics.
Description:
Mechanical recycling has been widely used to recover end-of-life (EoL) plastics. However, the existing plastic recycling infrastructure requires further improvement to prevent unwanted releases of plastic additives from the polymer matrix, exposing humans and the environment to many hazardous substances. Chemical processing is a promising EoL treatment for handling discarded plastics because it can chemically deconstruct the macromolecules into new products and feedstock to synthesize the original material. This action can effectively separate chemical additives from the original matrix, provided that appropriate separation techniques are used. This conference presentation shows current work on the fate of chemical additives throughout the conventional EoL chemical processing techniques, including pyrolysis, gasification, and depolymerization, by providing material flow, energy system, and generic scenario analyses. The material flow analysis shows that plastic additives could be released during polymer depolymerization and degradation because these molecules are not chemically linked to the original polymer chain. As a result, these chemicals may further react with substituents found inside the chemical recycling process units (e.g., reactors, dissolution tanks, etc.), synthesizing unwanted side products that may interfere with the quality of the final product and increase environmental releases of hazardous materials. The energy system analysis identified energy-saving potentials while ensuring the minimal generation of toxic chemical releases from each EoL chemical processing technique. Our generic scenario analysis estimates environmental releases and occupational exposures from operating a chemical recycling facility for plastics, along with the detailed EoL of all the materials involved, including monomers, additives, solvents, reagents, etc. In addition, this work evaluates the sustainability of the recycling process using The Gauging Reaction Effectiveness for the ENvironmental Sustainability of Chemistries with a multi-Objective Process Evaluator (GREENSCOPE). Therefore, this research demonstrates that chemical processing of the EoL plastics for potential reuse, although an excellent alternative to conventional mechanical recycling, requires further improvement to separate additives from plastics effectively and ensure the safety and sustainability of such technologies.