Microwave-Assisted Pyrolysis of Polyethylene and Polypropylene from End-of-Life Vehicles: Hydrogen Production and Energy Valorization

Grigore Psenovschi, Ioan Calinescu (), Alexandru Fiti, Ciprian-Gabriel Chisega-Negrila, Sorin-Lucian Ionascu and Lucica Barbes ()
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Grigore Psenovschi: Faculty of Chemical Engineering and Biotechnologies, National University of Science and Technology Politehnica of Bucharest, 011061 Bucharest, Romania
Ioan Calinescu: Faculty of Chemical Engineering and Biotechnologies, National University of Science and Technology Politehnica of Bucharest, 011061 Bucharest, Romania
Alexandru Fiti: Daily Sourcing & Research SRL, 011061 Bucharest, Romania
Ciprian-Gabriel Chisega-Negrila: Faculty of Chemical Engineering and Biotechnologies, National University of Science and Technology Politehnica of Bucharest, 011061 Bucharest, Romania
Sorin-Lucian Ionascu: Doctoral School of Biotechnical Systems Engineering, National University of Science and Technology Politehnica of Bucharest, 060042 Bucharest, Romania
Lucica Barbes: Doctoral School of Biotechnical Systems Engineering, National University of Science and Technology Politehnica of Bucharest, 060042 Bucharest, Romania

Sustainability, 2025, vol. 17, issue 13, 1-26

Abstract: Plastic waste is currently a major concern in Romania due to the annual increase in quantities generated from anthropogenic and industrial activities, especially from end-of-life vehicles (ELVs), and the need to reduce environmental impact. This study investigates an alternative valorization route for polypropylene (PP) and polyethylene (PE) plastic waste through microwave-assisted pyrolysis, aiming to maximize conversion into gaseous products, particularly hydrogen-rich gas. A monomode microwave reactor was employed, using layered configurations of plastic feedstock, silicon carbide as a microwave susceptor, and activated carbon as a catalyst. The influence of catalyst loading, reactor configuration, and plastic type was assessed through systematic experiments. Results showed that technical-grade PP, under optimal conditions, yielded up to 81.4 wt.% gas with a hydrogen concentration of 45.2 vol.% and a hydrogen efficiency of 44.8 g/g. In contrast, PE and mixed PP + PE waste displayed lower hydrogen performance, particularly when containing inorganic fillers. For all types of plastics studied, the gaseous fractions obtained have a high calorific value (46,941–55,087 kJ/kg) and at the same time low specific CO 2 emissions (4.4–6.1 × 10 −5 kg CO 2 /kJ), which makes these fuels very efficient and have a low carbon footprint. Comparative tests using conventional heating revealed significantly lower hydrogen yields (4.77 vs. 19.7 mmol/g plastic). These findings highlight the potential of microwave-assisted pyrolysis as an efficient method for transforming ELV-derived plastic waste into energy carriers, offering a pathway toward low-carbon, resource-efficient waste management.

Keywords: catalytic pyrolysis; polypropylene recycling; end-of-life vehicles (ELVs); activated carbon; waste-to-energy; environmental impact (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2025
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