Overcoming the drawbacks of waste plastic pyrolysis through chemical-biological processes

A joint research team has developed a technology to recycle mixed waste plastics to produce high-value-added plastic raw materials called dicarboxylic acids (α,ω-diacids). The study is published in the Journal of Cleaner Production.

The team was led by Dr. Sang-Goo Jeon from the Bioenergy and Resource Upcycling Laboratory at the Korea Institute of Energy Research (KIER) and Dr. Jung-Oh Ahn from the Bioprocess Engineering Center at the Korea Institute of Biological Sciences. (Crib)

Plastics are made from fossil fuels such as oil and natural gas, and waste plastics are crushed and melted and recycled into new products. However, during the production and processing stages, wastewater and hazardous substances are discharged, which has a serious impact on the environment.

To address these issues, many countries and companies are working to establish a plastic circular economy. Particularly recently, environmentally friendly recycling technology for plastics using chemical methods such as pyrolysis has been attracting attention.

However, pyrolysis is also not a perfect solution. Of the naphtha components contained in the pyrolysis oil produced during pyrolysis, only 30% is recycled as a plastic raw material, and the majority is used as a low-grade fuel that generates greenhouse gases when burned. It’s for a reason.

A Korean research team proposed a chemical-biological process that combines chemical and biological methods to overcome the limitations of traditional chemical recycling technology. The process developed this time does not use pyrolysis oil as a low-grade fuel, but instead refines it into normal paraffin, which becomes a raw material for microbial reactions, and uses it as a raw material for microorganisms to produce plastic raw materials.

By utilizing chemical pretreatment technology developed by the Korea Institute of Energy Research (KIER), it is possible to selectively refine only normal paraffins from pyrolysis oil. When pyrolysis oil reacts with a catalyst in a high-temperature environment of 400℃ filled with hydrogen, impurities and harmful substances are removed and it turns into normal paraffin.

After the purified normal paraffin is used as food for microorganisms, it is finally converted into dicarboxylic acid, which is used as a raw material for high value-added plastics such as polyester (PES), polyamide (PA), and polyurethane (PU).

The research team predicted that this technology could reduce the cost of producing plastic raw materials by up to 40% compared to existing petrochemical-based production techniques. Additionally, 30% of pyrolysis oil, typically used as low-grade fuel, will be recycled as plastic feedstock, benefiting the nation’s greenhouse gas reductions.

Dr. Chong said, “This technology overcomes the limitations of existing chemical plastic recycling methods, and is an achievement that can greatly contribute to establishing a circular economy for plastics and achieving carbon neutrality.Currently, we are using the dicarboxylic acids produced to synthesize plastics. We are conducting verification work to ensure that.” In the future, we plan to proceed with technology transfer and commercialization through collaboration with interested companies. ”