Environmental Burden of Household Plastic Waste Management under Municipality-Level Policy Adaptation: A Case Study of Okayama City, Japan

Plastic waste management has become a critical global environmental issue due to the slow degradation of plastics and the release of microplastics and harmful chemical additives. Among the available treatment methods, recycling is the most widely adopted in developed countries, offering a pathway to reduce virgin plastic production and its associated environmental impact. In Japan, municipal policies have a significant influence on household plastic waste treatment. Since March 2024, Okayama City has implemented a new policy introducing separate collection and intermediate processing of plastic resources for recycling. The environmental implications of this policy remain unclear. Existing literature consistently indicates that recycling outperforms incineration in most impact categories. Nevertheless, gaps remain in assessing the impacts of transportation and intermediate processing. To address these limitations, this study analyses four scenarios based on different collection rates and treatment options using the Life Cycle Impact Assessment (LCIA) Method based on Endpoint Modelling, tailored for the Japanese context. The results highlight that incineration imposes the greatest overall environmental burden, while recycling remains the least impactful. Recycling has the lowest damage potential to biodiversity, with the value 1×10-11 EINES, whereas incineration has the highest damage potential, with a value of 1×10-9 EINES. The findings aim to clarify the environmental burdens associated with plastic waste treatment in Okayama City and provide more sustainable waste management strategies. With the support of policy enforcement in Okayama City, recycling is the preferred pathway for plastic waste management.