Performance evaluation of liquid fuel derived from waste plastics for diesel engine applications and emissions characteristics

Conventional fossil fuels, such as diesel are commonly used to power vehicles and machinery in many industries, including transportation and agriculture. However, the demand for these fuels is increasing worldwide, especially in developing countries, raising concerns about long-term energy security and environmental impact. The use of hydrocarbon fuels is linked to air pollution and climate change, prompting research on alternative energy sources. This study explored the potential of using oil made from a mixture of four waste plastics (polypropylene, polystyrene, low-density polyethylene, and high-density polyethylene) as an alternative fuel for diesel engines and the effect of blending waste plastic oil with diesel (20 % waste plastic and 80 % diesel fuel-B20, 30 % waste plastic and 70 % diesel fuel-B30, and 50 % waste plastic and 50 % diesel fuel-B50) on fuel properties, engine performance, and engine emission characteristics. Fuel properties such as density and kinematic viscosity were evaluated and compared to baseline data obtained with pure diesel (100 % diesel fuel-B0). Engine performance like brake power, brake torque and brake specific fuel consumption and Emissions, including carbon monoxide (CO), Carbon dioxide (CO2), unburned hydrocarbon (UHC), and nitrogen dioxide (NOx), were also assessed. Both density and kinematic viscosity were observed to decrease as the proportion of waste plastic fuel in the blend increased, with values lower than those of pure diesel but higher than the minimum standard up to B50. The maximum gap between the pure diesel and its blend at the peak points for brake power and brake torque is 12 % (B30 at 3600 rpm) and 16% (B50 at 1150 rpm), respectively, in which diesel fuel is at the top. However, in terms of bsfc, B50 has the lowest consumption, which can reduce fuel consumption by up to 7 %. In case of emission, the waste plastic blend improved NOx emissions (except for B50), carbon dioxide, and unburned hydrocarbons by 3 % (B20 at 3600 rpm), 10 % (B50 at 1300 rpm), and 19 % (B30 at 1000 rpm), respectively. However, the CO emissions were slightly higher at low speeds and were nearly comparable at higher engine speeds. The economic analysis shows that the blends of waste plastic oil can substitute diesel respect to engine performance and energy output, provided the cost of these blends is 51 % lower than that of diesel.