- Combining pyrolysis + gasification to increase chemical recycling of waste plastics

- Successful conversion of waste plastics into high-value feedstock with integrated conversion process

A team of researchers led by Professor Myung Won Seo of the School of Environmental Engineering at the University of Seoul has developed a gasification technology that utilizes waste plastic pyrolysis oil to produce high-purity syngas. This technology is expected to be a major turning point in overcoming the limitations of waste recycling and creating new energy resources.

The research team’s “Fractionated Layer Gasification and Impurity Removal Process of Mixed Waste Plastic Pyrolysis Oil” is a method of pyrolyzing waste plastic and then gasifying it to remove impurities and produce high-value synthesis gas. 

The government of Korea recently stated that to meet its waste-to-energy target (1.7 million tonsCO2 per year), about 1 million tons of waste per year will need to be processed through pyrolysis/gasification. Because the amount of waste treated through pyrolysis in 2022 was 20,000 to 30,000 tons, the relevant market size is expected to increase about 50 times by 2050. In addition, the Korean Circular Economy Implementation Plan, prepared by the Ministry of Environment and the Ministry of Trade, Industry and Energy, announced plans to expand the share of waste plastic pyrolysis treatment from 1% in 2020 to 10% in 2030 and to shift the production of pyrolysis oil, which is currently fuel-centered, to feedstock-centered. 

However, the high impurity content of waste plastic pyrolysis oil has been a persistent problem, making it difficult to utilize industrially. To solve this problem, Prof. Myung Won Seo’s research team, in collaboration with the research team of Dr. Ho Won Ra, head of the Climate Change Division at the Korea Institute of Energy Research, proposed a gasification process to increase the utilization of waste plastic pyrolysis oil.

▶ Conceptual diagram of the waste plastic pyrolysis oil fractionated bed gasification and impurity adsorption system and monitoring system

The team won the grand prize for the “Waste Plastic Energy Production Plant” team at the 2023 Yonsei Technomics Audition contest and established close cooperation in the field of waste-to-energy. The technology is an integrated plant that can sort waste plastics and convert them into hydrogen fuel or chemical raw materials, an idea that was well received by the jury for its ability to solve environmental problems and energy supply at the same time. In this study, Seo’s team followed up on that work by implementing the technology at laboratory scale and confirming that it can be operated efficiently.

The team built a lab-scale, 1 kg/h classified bed gasifier, an impurity adsorption unit, and a real-time monitoring system. “It was difficult to build this classification layer gasifier, as it was my first device in the lab after entering the university,” said master’s student Tae Hwi An, the first author of the paper, adding that through numerous trials and errors, they created a stable operation and safe experimental environment. Through this device, the gasification characteristics and optimal operating conditions of waste plastic pyrolysis oil were analyzed, and further research will be conducted to improve the efficiency of reducing impurities in the syngas.

▶ (From left to right) Prof. Myung Won Seo, University of Seoul (co-first author); Ho Won Ra, Head of Korea Institute of Energy Research (co-first author); Tae Hwi An, MSc, University of Seoul (first author)

“Our research has shown the possibility of converting low-grade waste plastic pyrolysis oil into high-value syngas, which can be further processed and utilized as high-value fuels such as hydrogen, methanol, substitute natural gas (SNG), and sustainable aviation fuel (SAF),” said Prof. Myung Won Seo.

“This is an important step forward in solving the waste problem and achieving a sustainable energy transition at the same time,” said Dr. Ho Won Ra, who co-led the research.

The research was supported by a mid-career research project grant from the National Research Foundation of Korea, and the results were published in the December 2024 issue of the Journal of Environmental Chemical Engineering, an international journal in the field of environmental engineering and chemical engineering.