Technoeconomic and Life Cycle Analyses of the Co-production of Olefins, Aromatics, and Alkanes Using Microwave-Assisted Conversion of Polypropylene Plastic Waste

There is a growing interest in utilizing plastic waste to produce olefins and aromatics, which serve as essential building blocks for polyolefin production. In this paper, a novel microwave-assisted catalytic process is developed for converting polypropylene plastic waste into propylene, with simultaneous co-production of ethylene, aromatics, and alkanes, thereby closing the material loop by returning end-of-life plastic waste back into the petrochemical value chain as a high-value chemical feedstock, a key principle of the circular economy. A technoeconomic analysis conducted for several scenarios shows that the net present value of the proposed novel process ranges from a low value of USD 1332.56 million to a maximum of USD 2000.65 million at the investigated capacity, depending on co-product valorization and off-gas recovery for process heat generation. The sensitivity analysis performed reveals that the cost of the plastic waste feedstock and selling price of propylene are among the most influential parameters on the economics of the proposed plant. A life cycle assessment is then conducted for the novel plant, which is benchmarked against the simulated conventional propane dehydrogenation plant, whose calculated global warming potential amounts to 2.22 kg CO2-eq/kg propylene. Results show that the global warming potential of the novel plant ranges between 2.41 and 0.71 kg CO2-eq/kg propylene, depending on the carbon intensity of the electricity grid used and successive valorization of co-product streams. Overall, the economic viability and environmental sustainability of the proposed process are strongly contingent on the extent of co-product recovery. The proposed circular economy pathway of valorizing plastic waste into high-value chemicals via electrified microwave-assisted heating provides a compelling case for electrified, waste-based production routes as a sustainable alternative to conventional processes.