Quantifying the carbon circularity, climate and energy benefits of plastic recycling through circular flow analysis: Application to plastic packaging waste in Japan

Carbon circularity has attracted increasing attention alongside climate change impacts and fossil energy consumption in plastic recycling evaluations. Herein, we introduce the carbon flow and circular diagram (CFCD) method, a unified framework designed to assess plastic recycling by integrating carbon circularity, carbon neutrality, and fossil energy independence. CFCD visualizes carbon flows by mapping carbon inputs and outputs across various pathways. We apply our approach to the complex ecosystem of plastic packaging waste recycling in Japan. Our findings reveal that catalytic cracking preserves 56.8 % of carbon circularity, whereas mechanical recycling achieves moderate carbon circularity and climate benefit. High-efficient energy recovery delivers substantial climate and energy benefits with poor circularity. Gasification for ammonia production yields the highest energy benefit of 57.9 MJ/kg of waste yet is largely ineffective in improving carbon circularity, whereas the carbon capture and utilization emerges as a key strategy.