Full length articleFlows and waste reduction strategies of PE, PP, and PET plastics under plastic limit order in China
Introduction
Plastic pollution has always attracted global attention and is very common all over the world. It can be seen in the ocean, lakes, soil, rivers, and sediments (Lau et al., 2020). Although plastics have become one of the most widely used materials in the world, which can be seen everywhere in our life (Hopewell et al., 2009), they lead to waste accumulation, greenhouse gas emissions, pollution of the marine environment, etc. (Chu et al., 2022; Meys et al., 2021). The amount of poorly managed plastic waste produced by the coastal population of a country varies from 1.1 million tonnes to 8.8 million tonnes each year (Jambeck et al., 2015). Post-consumer plastics would become waste, which not only occupies a lot of land area but enters the ocean with rivers, seriously threatening the safety of the marine ecosystem. It is estimated that the cumulative amount of marine plastics in 2025 may be an order of magnitude higher than that in 2010 (Jambeck et al., 2015). Plastics will be decomposed into microplastic (less than 5mm) at all stages of their life cycle, which has seriously threatened marine organisms and is increasingly appearing in the human food system (Andrady, 2017, Jacob et al., 2020, Lau et al., 2020, Liu et al., 2009, Van Cauwenberghe et al., 2013). To alleviate the impact of waste plastics on the environment, it is very necessary to clarify the source and sink of waste plastics and flows information on plastics production, processing, manufacturing, use, recycling, and end of life. At present, the flows of plastics at national, regional, and even global scales have been concerned. In terms of national scale, Van Eygen et al. (2017) quantified the plastic flows in Austria from plastic production and consumption to the waste management stage based on material flow analysis (MFA). Flows and recycling of plastics in the United States were explored by Smith et al. (2022), and Liang et al. (2021) conducted high-resolution MFA of polyurethane in the United States in 2016 for the first time, including raw materials, production and manufacturing, trade, stocks, and waste treatment processes. Millette et al. (2019) conducted a study on the flows of plastics in Trinidad and Tobago. Bi et al. (2021) studied the flows and fate of phthalic acid esters used in polyvinyl chloride from 1958 to 2019 based on dynamic MFA in China. Chu et al., 2021a developed the flow model and framework of PET in China, including production, market trade, manufacturing and use, waste management and recycling stages. Nakatani et al. (2020) analyzed the flows of plastic packaging in Japan. They showed that industrial plastics were difficult to achieve the government's and the recycling goal, industrial and civil plastics also needed to be recycled. In addition, Kawecki et al. (2018) analyzed the static flows of plastic polymers in Europe, providing a strong basis for the exposure assessment of polymer-related effects. Eriksen et al. (2020) assessed the potential recyclability of Polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) in Europe. For the global scale, a global analysis of plastics by creating a comprehensive flow model was conducted from the production, use, and service life of polymer resins, synthetic fibers, and additives, which provided useful information for understanding the plastics cycle (Geyer et al., 2017). Lau et al. (2020) simulated the stocks and flows of global municipal waste and four microplastics from 2016 to 2040. They found that concerted global actions would be urgently needed to reduce plastics consumption, improve the rate of reuse, collection, and recycling, and accelerate the innovation of the plastic value chain.
PE, PP, and PET have become the most critical engineering polymers in the world due to their excellent thermal stability, lightweight, and easy storage (Chu et al., 2021b; Rahmani et al., 2013). PE, PP, and PET are the most widely used plastics in China, and China's plastic limit order has the most significant impact on these three plastics. Notably, the Chinese government issued a plastics limit order to implement the policy requirements of "banning and limiting one batch, replacing and recycling one batch, and standardizing one batch", which will have an important impact on the flows of PE, PP, and PET (NDRC, 2020). However, under the plastics limit order, the change characteristics of flows, stocks, and waste of these plastics in China are unknown, and the potential and specific strategies for waste reduction are missing. Therefore, we applied a dynamic modeling approach to explore the characteristics of flows, stocks, and waste of these plastics in 2017 and then considered the impact of the plastic limit order on these plastics, and we analyzed the trajectory scenarios of plastics use and waste from 2018 to 2030, as well as the corresponding strategies for waste reduction. There are two main innovations in this study: 1) building the material flow model for multiple types of plastics life cycle under the plastic limit order; 2) according to China's plastic limit policy, the scenario analysis of PET, PE, and PP plastics was carried out, and the specific strategies for waste reduction were obtained. This study clarified the flows and stocks characteristics of these plastics in China under the plastic limit order, as well as the main sources and reduction potential for waste, and proposed strategies for waste reduction, which will provide scientific support for the specific implementation of the plastic limit order and realizing the waste reduction goal.
Section snippets
The dynamic MFA model for PE, PP, and PET
The system boundary of plastics MFA in this study includes the spatial boundary (the Chinese mainland (excluding Hong Kong, Macao, and Taiwan)) and the time boundary (2017-2030). This study constructed the MFA model and recycling system of plastics. The system mainly includes four stages: production (P), processing and manufacturing (PM), use (U), and waste management and recycling stages (WM&R). Considering the availability of data, the base year is 2017, and we simulated the flows, waste, and
Flows and stocks of PE, PP, and PET in the life cycle
We found that the production of PET was the largest among the three plastics, accounting for 54% of the total in 2017, while the production of PP (25%) and PE (21%) was relatively low. Meanwhile, the total consumption of these plastics reached 85.05 Tg. PE and PP imports were higher than exports, with net imports of 11.55 Tg and 2.88 Tg, respectively. However, the import of PET was lower than the export, with a net export of 5.13 Tg. This showed that domestic consumption of PE and PP in China
Conclusions
This study established a life-cycle flow model and framework for PET, PE, and PP in China, and the potential and specific strategies for waste reduction are proposed under the plastic limit order. We found that PE film, PE STP&C, PP WG, and PET fiber are the main primary products. The B&C is the sector with the largest stock of PE and PP, while the stock of PET is mainly in textiles. If plastic waste is not controlled under the BAU, the total amount will reach 128.84 Tg, an increase of 116%
CRediT authorship contribution statement
Jianwen Chu: Conceptualization, Data curation, Methodology, Investigation, Writing – original draft. Ya Zhou: Conceptualization, Methodology, Writing – review & editing, Supervision. Yanpeng Cai: Conceptualization, Methodology, Writing – review & editing, Supervision. Xuan Wang: . Chunhui Li: . Qiang Liu: .
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This research was supported by the National Natural Science Foundation of China (U20A20117), the Key-Area Research and Development Program of Guangdong Province (2020B1111380003), and the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) (GML2019ZD0403). We are deeply grateful to the reviewer for his/her careful review. His/her suggestions have greatly helped improve the paper.
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