(161a) Techno-Economic Analysis and Life Cycle Assessment of Non-Thermal Plasma Co-Upcycling of Waste Plastics and CO2 to High-Value Chemicals

Single-use plastic waste is accumulating rapidly in landfills and oceans, causing significant harm to the environment and human health. In the United States, over 80% of plastic waste ends up in landfills, while around 30% of it is dumped into the oceans, posing a severe threat to the ecosystem^1,2. Single-use plastics are mainly composed of polyolefins, polyethylene (PE) and polypropylene (PP), manufactured from fossil fuels. Therefore, plastic waste contains a significant amount of carbon, which has the potential to be recovered and converted into valuable products at the end of its life cycle. However, this potential is often limited due to inefficient waste management practices and a lack of cost-effective recycling methods.

Plastic upcycling into value-added products can establish a circular economy for plastics and mitigate the environmental burden caused by their end-use and disposal. Non-thermal plasma has gained recognition as an effective chemical upcycling technology to convert plastic and CO₂ waste to valuable chemical commodities^3,4. However, the technical and economic feasibility of employing this technology for plastic waste treatment has not been thoroughly investigated yet.

In this study, we conducted the techno-economic analysis (TEA) and life cycle assessment (LCA) of a non-thermal plasma technology that upcycles plastic waste and waste CO₂ to oleochemicals and hydrocarbons. A conceptual facility with a daily processing capacity of 200 metric tons (MT) of waste PE with a 20-year lifetime was designed. The process was modeled based on the experimental results at the laboratory scale. The process simulations, mass and energy balance, and TEA analysis were performed with the open-source platform BioSteam 2.38.6.

The study evaluated two plasma carrier gas compositions: CO₂ plasma (scenario 1) and CO₂/O₂ plasma (scenario 2). The decomposition of waste PE through CO₂ and CO₂/O₂ plasma processes results in the production of both liquid and gaseous products. The liquid product comprises fatty alcohols, fatty acids, fatty aldehydes, olefins, and paraffins while the gas yield includes carbon monoxide, hydrogen, and C₁-C₅ hydrocarbons. All the liquid compounds are recovered in the process, and the gases are combusted to generate energy for the plant operations.

All the scenarios were economically feasible, with an internal rate of return (IRR) ranging from 42.4% to 43.7% in favor of scenario 2. The TEA showed that the total installed cost of CO₂ plasma and CO₂/O₂ plasma were respectively $52.7 million and $56.9 million. The annual revenue of scenarios 1 and 2 were $145 and $163.7 million respectively. The net present value (NPV) was $744.4 million and $857 million, respectively.

The LCA was performed in OpenLCA 1.11.0 and the EcoInvent database. The global warming potential ranged from -1.9 to -0.73 kgCO2e/kg PE. Negative emissions were achieved in all scenarios, as the credits earned from the products surpassed the carbon emissions generated in the refinery. Sensitivity analysis showed that capital cost and fatty alcohol price have a significant impact on the profitability of the facility, while utilities and the production of fatty alcohols and olefins have the most significant impact on the environmental factors.

These findings indicate that non-thermal plasma is a viable alternative for the upcycling of plastic waste and CO₂ waste. This technology has great potential to produce carbon-negative chemicals, reducing our dependence on petrochemicals.

Acknowledgments: This research is supported by the Department of Energy Office of Energy Efficiency and Renewable Energy under contract no. DE-EE0009943. We thank our collaborators, Dr. Xianglan Bai and her student Harish Radhakrishnan, for performing the experimental work for the project.

References

1. United States Environmental Protection Agency (U.S. EPA). Plastics: Material-Specific Data; U.S. EPA: Washington, D.C., 2023; https://www.epa.gov/facts-and-figures-about-materials-waste-andrecycling... (accessed Oct 20,2023).
2. Yadav B, Pandey A, Kumar LR, Tyagi RD. Bioconversion of waste (water)/residues to bioplastics- A circular bioeconomy approach. Bioresour Technol. 2020;298:122584. doi:10.1016/j.biortech.2019.122584
3. Nguyen HM, Carreon ML. Non-thermal Plasma-Assisted Deconstruction of High-Density Polyethylene to Hydrogen and Light Hydrocarbons over Hollow ZSM-5 Microspheres. ACS Sustain Chem Eng. 2022;10(29):9480-9491. doi:10.1021/acssuschemeng.2c01959
4. Bogaerts A, Neyts EC. Plasma Technology: An Emerging Technology for Energy Storage. ACS Energy Lett. 2018;3(4):1013-1027. doi:10.1021/acsenergylett.8b00184