(385a) Preliminary Techno-Economic Analysis of PET Electro-Reforming Process

This study aims to examine the techno-economic-environmental criteria of the Polyethylene terephthalate (PET) electro-upcycling process. To achieve this goal, we developed PET electro-reforming process involving enzymatic depolymerization and electrochemical technologies to produce value-added chemicals (e.g., terephthalic acid, glycolic acid, hydrogen) from recycled PET flakes as a feedstock. With the developed process, we evaluated the economics of the process based on the minimum selling price (MSP) of terephthalic acid and glycolic acid and environmental impact of the process based on net CO₂ equivalent emission (NCE). Also, we performed sensitivity and uncertainty analysis to identify the feasibility of the process with the fluctuation on major parameters. As a result, proposed process demonstrates economic feasibility with low NCE. Consequently, PET electro-upcycling process can be regarded as an effective pathway for chemical upcycling of PET.

PET is indispensable product which is widely used for food packaging, disposable medical equipment, and daily necessities [1]. With its high usability and great physical properties, annual worldwide market volume of PET has increased to 25.47 million metric tons (MMT) and is expected to increase continuously [2]. However, this substantial production volume generates significant waste, leading to persistent pollution to the ecosystem. In this regard, developing effective, economic technology for recycling is crucial to addressing the plastic waste problem. Recently, PET electro-reforming technology has emerged as a solution with considerable advantages (e.g., controllability of reaction rates by managing applied voltage, wide adaptability due to modular electrolyzer designs, and compatibility with depolymerization process of PET) [3]. While active research is being conducted at the lab scale, the economic and environmental impacts of this technology at an industrial scale remain uncertain. Thus, the development of PET electro-reforming process on an industrial scale is necessary to evaluate the feasibility of the process.

The goal of this study is to examine the techno-economic-environmental performance of PET electro-reforming process. To achieve this goal, we developed the PET electro-reforming process which selects recycled PET flakes as a feedstock to produce Terephthalic acid (TPA), Glycolic acid (GA) as a main product by employing several technologies. The technologies include reaction and conversion technologies (e.g., enzymatic depolymerization, electrolysis), component separation (e.g., acidification, filtration, membrane), and product purification (e.g., centrifugation, flash drum, distillation column). The process flow diagram of this study is shown in the Figure. In this study, we evaluated economic feasibility of the PET electro-reforming process using minimum selling price (MSP) of TPA and GA. The MSP includes total capital investment (TCI), total operating costs (TOC), and profits from by-products (i.e., H₂ and K₂SO₄). Expenses related to electrolysis (e.g., electrolyzer capital cost, BoP capital expenditures and stack replacement interval) are estimated based on the H2A production case study report [4]. The mass and energy information along with sizing and cost information is obtained by process simulation using Aspen plus V.12. To evaluate environmental impact of the process, net CO₂ equivalent emissions (NCE) is used. In this process, we only consider indirect CO₂ emissions related to utility consumption, as there are no direct CO₂ emissions. We also performed the sensitivity analysis to investigate major cost and environmental drivers of the process. Finally, we performed uncertainty analysis based on Monte Carlo (MC) simulation to determine the feasibility of the process with the cost fluctuation on major cost drivers [5]. From the MC simulation, a probability range of MSP is observed, so that economic competitiveness of the process is identified.

In this study, we developed a PET electro-reforming process and evaluated the process from a techno-economic-environmental perspective. Compared to the current market prices of the main products, the MSPs of TPA and GA from our developed process show negligible differences. The recycling of electrolyte and unreacted reactant enhances the overall efficiency of the process. Major cost contributors that significantly influence the MSP include the price of PET, GA, K₂SO₄, and KOH as well as the interest rate and the faradaic efficiency of electrolysis. Through sensitivity and uncertainty analysis, we have also revealed that process competes economically within the range of cost fluctuations. Additionally, NCE of the process is low due to low energy consumption for heating and the use of renewable electricity. In addition, the early-stage evaluation of the PET electro-reforming process provides valuable insights into the economic and environmental feasibility of the technology, as well as its potential for future utilization.

Reference

[1] Rahimi, A.R., and J.M. Garciá, “Chemical recycling of waste plastics for new materials production,” Nature Reviews Chemistry 1, 2017..

[2] Bescond, A.-S., and Pujari, A. (2020). PET polymer. In Chemical Economics Handbook (IHS Markit), p. 32. https://ihsmarkit.com/ products/chemical-economics-handbooks. html.

[3] Jouny, M., W. Luc, and F. Jiao, “General Techno-Economic Analysis of CO2 Electrolysis Systems,” Industrial and Engineering Chemistry Research, 57 (6), pp. 2165–2177 (2018).

[4] D. Peterson, J. Vickers, and D. DeSantis, “Hydrogen Production Cost from PEM Electrolysis - 2019”, (2020).

[5] Do, T.N., H. Kwon, M. Park, C. Kim, Y.T. Kim, and J. Kim, “Carbon-neutral hydrogen production from natural gas via electrified steam reforming: Techno-economic-environmental perspective,” Energy Conversion and Management, 279, (2023).