(154aq) Evaluating the Economic and Environmental Benefits of Deploying a National-Scale, Thermo-Chemical Plastic Upcycling Infrastructure in the United States

Global rates of plastic production, today reaching 380 million tons per year [1], demand comprehensive and reliable plastic waste management systems to avoid the worst impacts of terrestrial and marine plastic pollution [2]. However, overall plastic recycling rates remain well below 10% [1], while the bulk of plastic wastes are incinerated, landfilled, or allowed to accumulate in the biosphere [3].

Traditional plastic recycling by mechanical methods is a mature technology but faces significant inadequacies as a plastic management strategy given that it has been developed only to accept limited types of plastics (mainly polyethylene terephthalate and high-density polyethylene, or PET and HDPE), which generally represent less than 12% of consumer plastic waste [4]. Furthermore, its products are of lower quality than its starting materials [5]. The result of this “downcycling” of plastic materials is an unsustainable system in which inputs can only be recycled a finite number of times before having no remaining use [6]. These factors reinforce the parallel need for environmentally-damaging disposal methods such as landfilling and incineration to accept the waste products not fit for downcycling.

An alternative strategy for plastic waste management, known as plastic “upcycling,” uses chemical methods rather than mechanical ones. Upcycling involves a chain of processing technologies: beginning with the sorting and purification of plastic fractions of common recyclable waste streams at municipal recovery facilities (MRFs) and plastic reprocessing facilities (PRFs), plastic wastes undergo a series of thermo-chemical conversions including pyrolysis and steam cracking to arrive at pure plastic monomers, which can finally be repolymerized into products (here, low-density polyethylene and polypropylene, or LDPE and PP) with the same properties as virgin plastics [1]. This capability of forming identical quality products provides a central contrast with traditional mechanical recycling: chemical upcycling is a strategy which approaches a circular plastics economy, while mechanical downcycling does not. Moreover, the thermo-chemical approach provides a flexible avenue to deal with diverse plastic waste types that cannot be mechanically recycled.

In order to accelerate the deployment of plastic upcycling technologies, it is necessary to study its economic viability and its integration with existing waste management infrastructure. Ma et al. [4] recently investigated the implementation of upcycling technologies in the US Midwest region, but no studies have been reported on economic potential at a national scale. Studying economic viability at a national scale is important because it is necessary to determine if there is sufficient plastic waste feedstock available to justify large capital investments and because it is necessary to understand potential regional synergies that can help reduce costs, improve environmental outcomes, and ultimately lead to more circular plastic economies.

Our study uses a large-scale computational framework that integrates techno-economic analysis, value chain analysis, and optimization to examine the potential of deploying an upcycling infrastructure at a national scale. Our results indicate that upcycling provides a vastly more favorable economic picture than current downcycling infrastructure; specifically, we find that deploying an upcycling infrastructure can activate a value chain that generates significant revenue to diverse stakeholders (e.g., chemical industry, waste collectors, and material recovery facilities). Our analysis also finds that deploying such an infrastructure can lead to significant environmental benefits over the common disposal methods of landfilling and incineration.

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