A Cluster Analysis of Cooperative Recycling Behaviors for Post-Consumer Plastic Waste in Urban Areas: A Case Study on Sendai, Kawasaki, and Kyoto City in Japan

Post-consumer plastic waste poses increasing challenges in urban areas, where recycling heavily relies on consumer cooperation. In Japan, two recycling routes for post-consumer plastic waste from households exist, the municipal recycling route and the retailer recycling route, with the latter requiring more voluntary effort. This study aims to explore the diversity of consumers’ cooperative behaviors in Japan’s post-consumer plastic waste recycling system, with a focus on the retailer route. We conducted an online survey with 758 respondents from Sendai, Kawasaki, and Kyoto in urban Japan, using a structured questionnaire based on the knowledge–attitude–practice (KAP) framework. K-means clustering was conducted to identify behaviorally distinct consumer groups. Three clusters were revealed: Fully Engaged Consumers, Knowledge-Driven Consumers, and Passively Engaged Consumers. These groups exhibited distinct differences in cooperative recycling behaviors and socio-demographic characteristics. Our findings demonstrate the heterogeneity of consumer cooperation and underscore the importance of targeted strategies. By focusing on the retailer recycling route and consumer segmentation, this study addresses key gaps in Japan’s research on urban plastic waste. The results provide a theoretical and empirical foundation for differentiated policy-making, ultimately supporting the transition to a more sustainable and circular economy in post-consumer plastic waste recycling in urban Japan.