(301d) Economic Evaluation of Infrastructures for Pyrolysis-Based Upcycling of Plastic Waste

Plastics are indispensable to modern life. They possess important material properties that make them well suited to use in medical products, energy efficient construction materials, and food-contacting films and packaging, among other uses [1]. Plastics have provided cost-effective solutions, changing how we live and work; as a result plastics production has increased more than twenty times between 1960 and 2020 [2-3]. Disturbingly, in the same time period plastic waste generation has increased ninety times [4]. As of 2016, it is estimated that per capita plastic waste generation in the US was 130 kg/year [5], roughly equivalent to the weight of two average adults.The massive growth in waste illustrates failures in plastic waste management. While 30% of all plastic ever produced remains in use, 55% has been discarded, and only 6% has been recycled [6]. With no viable means to mitigate plastic waste, multiple studies now cite plastic waste as a global threat [7-9]. Meanwhile, demand for plastic products is still increasing [10-11] and recycling capacity is falling further behind; the accumulation of mismanaged plastic waste will continue to outpace efforts to address plastic pollution [12-13].

Chemical plastic processing provides a potential solution to intervene in the plastic waste supply chain, processing plastic wastes to recover high-purity chemicals, recycling materials back into valuable products [14]. We see this as a valuable opportunity to decrease global needs for virgin materials and to mitigate wastes entering terrestrial ecosystems. Among chemical recycling technologies, pyrolysis has gained recent attention [15].Pyrolysis processes involve chemical decomposition of long-chain polymers into smaller molecules at high temperatures under anoxic conditions. Many of the smaller molecules have value as commodity chemicals (e.g., ethylene). Part of the current interest in pyrolysis comes from its robustness; pyrolysis processes can handle mixed waste streams [14] and produce pyrolysis oil, a crude hydrocarbon product that can be refined into valuable fuels.[15], Notably, pyrolysis has a much lower carbon footprint than combustion [16].

Existing research into pyrolysis has primarily focused on reactor design [17], process intensification [18-19],catalyst selection [20-21], and techno-economic analysis (TEA) [22-23]. However, there is no systematic analysis that integrates TEA of recycling technologies with the design and operations of a complete plastics recycling infrastructure. Plastic collection, sorting, cleaning, chemical transformation, and transportation should be considered when assessing the economics of new infrastructure. Moreover, pyrolysis oil is usually evaluated as a transportation fuel [24-26]. However, it is also possible to recover monomers from waste plastics, closing the loop and circularizing the plastics supply chain [27]. The economics of plastics recycling are of interest. In Germany, for example, consumers receive incentive payments for plastic bottles returned to recycling centers, [28] while in the US consumers pay for recycling services through taxes.To our knowledge, no existing research has explored the plastics supply chain from this economic perspective to determine the inherent value in plastic waste. As a result, it is not clear how and whether incentives for consumers will increase the efficiency of plastics recycling programs.

In this session, we will present results combining TEA and economic supply chain modelling in which we explore the viability of pyrolysis-based plastics recycling supply chains in the American Midwest. Our optimization framework determines optimal facility sizes and locations for supply chain infrastructure, accounting for economies of scale and logistics, and maximizes the total surpluss (profitability) over the entire supply chain. By comparing plastic recycling strategies, our analysis provides insights into the economic viability of recycling infrastructure including consumer incentives. In our proposed model, recycling infrastructure is interpreted as a coordinated market, facilitating the discovery of the inherent value of plastic waste and of intermediate products (e.g., pyrolysis oil). This information can be used to determine how to remunerate supply chain stakeholders involved in plastic upcycling infrastructure.

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