Environmental impact of waste plastic oil and hydrogen-enriched diesel engines: A comprehensive review on performance, combustion, and emissions

This review focuses on the sustainable use of waste plastic by converting it into waste plastic oil (WPO) through catalytic pyrolysis. The primary objective is to explore the potential of WPO, derived from used polyethylene terephthalate bottles, as an alternative fuel for diesel engines. This review also evaluates WPO's physical and chemical properties, revealing that it possesses fuel attributes similar to those of petroleum-based fuels. Catalytic pyrolysis is employed on a laboratory scale, using catalysts such as silica, Zeolite Socony Mobil-5 (ZSM-5), alumina, and kaolin to extract WPO from mixed waste plastics. However, direct use of WPO in diesel engines has shown drawbacks, including significant combustion delays and increased emissions. To address these issues, this review suggests blending WPO with diesel fuel rather than using it as a standalone fuel. Furthermore, the review explores hydrogen enrichment in WPO blends to improve combustion efficiency. Hydrogen enrichment enhances thermal efficiency and reduces environmental emissions, showing potential for improved performance and lower brake-specific fuel consumption. This review presents a comparative analysis of various WPO blends with hydrogen enrichment, highlighting the benefits of incorporating hydrogen to boost combustion and performance. Although promising, further research is needed to ensure the sustainability and effectiveness of WPO blends as a long-term energy source.