Recycling of Plastics in the United States: Plastic Material Flows and Polyethylene Terephthalate (PET) Recycling Processes

Abstract

As efforts are made toward establishing a circular economy that engages in activities that maintain resources at their highest values for as long as possible, an important aspect is understanding the systems which allow recycling to occur. In this article a common plastic, polyethylene terephthalate, i.e., PET or plastic #1, has been studied because it is recycled at relatively high rates in the U.S. as compared to other plastics. A material flow analysis is described for PET resin showing materials collected, reclaimed for flake, and converted into items with recycled content. Imports/exports, reclaimer residue, and disposal with mismanaged waste are all shown for U.S. flows of PET. Barriers to recycling PET exist in the collecting, sorting, reclaiming, and converting steps, and this article describes them, offers some solutions, and suggests some research that chemists and engineers could focus on to improve the systems. This effort also models sorting at material recovery facilities (MRF) and reclaimers, with detailed descriptions of the material streams involved, to characterize the resource use and emissions from these operations that are key processes in the recycling system. Example results include greenhouse gas intensities of 8.58 kg CO2 equiv per ton of MRF feed and 103.7 kg CO2 equiv per ton of reclaimer PET bale feed. The results can be used in system analyses for various scenarios and as inputs in economic input-output and life cycle assessments.

Material Flow Analysis and Life Cycle Assessment of Polyethylene Terephthalate and Polyolefin Plastics Supply Chains in the United States

“…The PP material collected for sorting originates mainly from the containers and other packaging materials such as lids, caps, trays, baskets, and so on. Many studies have been published previously identifying the main challenges and opportunities to promote recovery and recycling of plastics at their EOL. ,,− For more information on interpretation of material flows, please refer to Section 6.2 of the SI-1 document and Figure S14 for complete composition of U.S. plastic waste generation by resin type and EOL product categories.…”

Rational Design of Chemical Catalysis for Plastic Recycling

“…However, the complicated purification of TPA and the harsh reaction conditions for the hydrolysis process severely limit its industrial application. For example, the reaction temperature and pressure for neutral hydrolysis are in the range of 388–693 K and 10–480 bar, respectively. − Most works of neutral hydrolysis occur in the noncatalyst systems, and some studies used metal salts as the catalyst . For example, Liu and co-workers used a homogeneous catalyst of Zn­(OAc) 2 to hydrolyze PET at 533 K, and the TPA yield can reach 20% within 1 h .…”

“…31−33 Most works of neutral hydrolysis occur in the noncatalyst systems, and some studies used metal salts as the catalyst. 34 For example, Liu and co-workers used a homogeneous catalyst of Zn(OAc) 2 to hydrolyze PET at 533 K, and the TPA yield can reach 20% within 1 h. 35 Wang et al reported that the high concentration of 70%ZnCl 2 /H 2 O can significantly accelerate the PET hydrolysis rate. The yield and purity of TPA reached up to 98.31% and 97.14% at 453 K for 8 h, respectively.…”

Optimisation of PET glycolysis by applying recyclable heterogeneous organocatalysts

“…With the help of experimental design, the numerous methods and catalysts used in PET glycolysis can be compared and evaluated more efficiently. Chen and co-workers applied a 2 3 factorial experimental design to study the two-and three-factor interaction effects of reaction temperature, catalyst:PET ratio, and reaction time on the glycolysis of PET. They used cobalt acetate or manganese acetate as catalysts.…”