Plastic waste to liquid fuel: A review of technologies, applications, and challenges

One of the most promising approaches for converting waste plastics into oil is fast pyrolysis. This study reviews the current state of the art and recent progress made on the thermal conversion of plastic to oil technologies, and their uses as alternatives to fossil fuels. The fuel properties of waste plastic pyrolysis oil (WPPO) are close to the diesel fuel. The WPPO produced from high-density polyethylene, low-density polyethylene, polypropylene, and polystyrene have higher heating values ranging from 40 to 43 MJ/kg. The thermal efficiency of neat WPPO (or blends) was slightly lower than diesel or gasoline. The WPPO has a shorter ignition delay than diesel due to its high cetane number. The WPPO fuels have a lower peak in-cylinder pressure and heat release rate than diesel. Engine-out emissions such as smoke, CO, and CO ₂, are lower than diesel. The NO _x emissions are higher than diesel, which can be reduced with exhaust gas recirculation or use of additives. Our study reveals that the WPPO is a promising alternative fuel for diesel engine applications.