Plastic-made diesel (PMD) from pyrolysis via vacuum distillation process: a waste recycling fuel to diesel engine performance and emissions improvement

Plastic applications are remarkably increasing nowadays; thus disposal of waste plastic and its negative environmental impact is a great challenge. Turning waste plastic into useful diesel as an alternative to petroleum fuel in the diesel engine is very attractive for communities in terms of waste plastic recovery and reduction in dependency on fossil fuel. This study conducted experiments to evaluate the engine performance and emissions using plastic-made diesel (PMD) which was produced from pyrolytic crude oil of a mixture of high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS) with equal proportion using a vacuum distillation process. The pyrochemical properties of PMD were first evaluated after distillation and tabulated. Then, three different ratios (5%, 10% and 20%) of PMD with ultra-low sulfur diesel (ULSD) were used as a diesel engine fuel to investigate engine performance and emission characteristics at variable speeds and loading operations. Results showed that the brake power (BP), torque and brake thermal efficiency of the engine with PMD20 were 2.9%–3.84%, 3.01%–3.21% and 3.9%–4.74% higher than those with ULSD at all tested conditions. The brake-specific fuel consumption (BSFC) of the engine using PMD20 decreased by about 3.77% compared to the engine using ULSD, thereby indicating less fuel usage at various load circumstances than the ULSD. Furthermore, CO emissions from PMD20 were 14.51% lesser than ULSD, and about 7.8% and 4.22% lesser than from PMD5 and PMD10 at all loading operations, respectively. The HC emissions of PMD20 were 15.1%–18.7% lower than that of the ULSD. The NOx emissions decreased by 2.06%, 3.01% and 3.95% on PMD blends PMD5, PMD10 and PMD20 compared to ULSD. These analyses demonstrate that PMD is a potential alternative fuel for engines and provides a useful means to recover the waste plastics.