Thermophysicochemical evaluation of waste LDPE-derived pyrolysis oil compared with market-grade diesel and petrol

The increasing accumulation of low-density polyethene (LDPE) waste poses a significant environmental challenge, requiring sustainable valorisation strategies to convert it into valuable energy resources. In this study, municipal LDPE waste was cleaned, dried, and thermally decomposed in a stainless-steel thermoprocessing reactor at approximately 450 °C under an inert nitrogen atmosphere. The resulting vapours were condensed to obtain LDPE-derived pyrolysis oil, which underwent comprehensive thermophysical and chemical characterisation, including density, sulfur and moisture content, aniline point, cetane number, boiling range, calorific value, olefin content, flash point, and corrosion behaviour, and was compared with commercial-grade petrol and diesel. The produced fuel exhibited a density of 0.804 kg/cm³ , a calorific value of 42.4 MJ/kg, a cetane number of 65.3, sulfur content of 43 ppm, moisture content of 2 ppm, and a boiling range of 51–340 °C, indicating a mixture of petrol- and diesel-range hydrocarbons. The low sulfur and moisture levels confirm its clean-burning nature, while the high cetane number reflects good ignition quality. Comparative analysis shows that several properties of pyrolysis oil fall within or near conventional fuel specifications. The observed composition aligns with the LDPE thermo-cracking mechanisms dominated by β-scission, hydrogen abstraction, and back-biting reactions. Overall, this study demonstrates that LDPE-derived pyrolysis oil has promising thermophysical and chemical characteristics and can serve as a supplementary fuel after appropriate upgrading and blending.