This research utilizes the characteristics of terahertz waves, used in next-generation communications and autonomous driving, to identify the materials of plastic waste. It improves existing recycling technologies and can be applied to evaluate the quality of recycled plastics, ensuring stable production of high-quality recycled plastics. It enables easy development of devices to solve various issues in containers and packaging and automobile recycling, contributing to the realization of decarbonization and a circular economy.

Conventional plastic waste identification and sorting technologies use specific gravity sorting or near-infrared devices. Particularly, near-infrared sorting technology has accumulated an enormous amount of data and serves as the primary sorting technology in plastic recycling plants. However, near-infrared devices struggle with identifying black plastics, additives, and degradation. This technology uses terahertz waves to measure and evaluate transmission and absorption characteristics, allowing for identification of black plastics, additives, and degradation.

• In recent years, there has been increasing global attention on plastic waste issues, such as marine pollution from drifting garbage and microplastics, the overseas export of plastic waste resources, and the increase in disposable containers like plastic bags and straws, especially due to the impact of COVID-19. There is growing demand for advanced identification and recycling of plastic waste materials, especially in the context of achieving the Sustainable Development Goals (SDGs) and realizing a circular economy.
• The research group from Tohoku University, Shibaura Institute of Technology, and Shizuoka University has conducted research on the commercialization of advanced sorting devices for plastic packaging waste. We have successfully identified mixed plastics containing black plastics, additives, and flame retardants, which were difficult to identify with existing devices, by utilizing the characteristics of terahertz waves. We have also confirmed the ability of terahertz waves in assessing degradation caused by UV or long-term use. Furthermore, the method has been shown to be effective for distinguishing bioplastics, which is expected to see increasing demand in the future, in addition to plastic waste from container packaging, automobiles, and home appliances.
• These identification technologies can be applied to properly sort plastic waste generated by the “The Plastic Resource Circulation Act,” enacted in 2022, contributing greatly to securing high-quality recycled resources through plastic waste resource recycling.
• Our research group conducts interdisciplinary research with experts in various fields: social engineering, resource circulation (Professor Jeongsoo YU), optical engineering (Professor Tadao TANABE of Shibaura Institute of Technology and Professor Tetsuo SASAKI of Shizuoka University), information science and big data analysis (Associate Professor Kazuaki OKUBO), data collection and analysis, international cooperation (Specially Appointed Lecturer Gaku MANAGO), social experiments, and behavioral economics (Assistant Professor Xiaoyue LIU). We address the needs from social, economic, and environmental issues both domestically and internationally, working from diverse perspectives to solve challenges and contribute to the creation of a sustainable society. Collaboration and networking with private companies, government agencies, research institutions, and civic organizations are also expected.

This technology can be applied to the development of plastic waste identification and sorting devices from processes such as containers and packaging recycling, automobile recycling, and home appliance recycling, as well as the production and quality evaluation of recycled plastics.