The increasing accumulation of plastic waste presents a critical environmental challenge that necessitates innovative and sustainable management strategies. This study investigates the conversion of waste plastics into biodiesel-like fuel through pyrolysis and evaluates its physicochemical properties and performance in a compression ignition engine. Waste plastic feedstock, primarily consisting of polyethylene and polypropylene, was subjected to thermal degradation under controlled conditions to produce liquid fuel. The resulting fuel was blended with conventional diesel at different ratios (B10, B20, and B30) and analyzed using standard ASTM procedures. The experimental results indicate that the produced fuel exhibits calorific values comparable to diesel, with moderate deviations in viscosity and density. Engine performance analysis reveals that lower blends, particularly B10, maintain brake thermal efficiency close to that of diesel, while higher blends result in increased fuel consumption due to reduced energy content and combustion inefficiencies. Emission analysis shows a rise in carbon monoxide and hydrocarbon emissions with increasing blend ratios, whereas nitrogen oxides exhibit an upward trend due to elevated combustion temperatures. Overall, the findings suggest that waste plastic biodiesel can be utilized as a supplementary fuel in diesel engines without significant modifications at lower blending levels. However, optimization of fuel properties and emission control strategies remains essential for broader applicability. This study contributes to the development of sustainable waste-to-energy technologies by integrating fuel production, characterization, and engine evaluation within a unified framework.

The present investigation examined the feasibility of converting waste plastics into biodiesel-like fuel through pyrolysis and evaluated its suitability for use in compression ignition engines. By integrating fuel production, physicochemical characterization, and engine performance analysis within a unified experimental framework, the study offers a more comprehensive perspective on the practical applicability of plastic-derived fuels. The results indicate that waste plastic biodiesel (WPB) possesses energy characteristics broadly comparable to conventional diesel fuel, with calorific values in the range of 41–42 MJ/kg. This relatively small deviation suggests that the fundamental energy potential of the fuel remains intact despite differences in chemical composition. At the same time, measurable variations in viscosity and density were observed, reflecting the presence of heavier hydrocarbon fractions and unsaturated compounds typically associated with pyrolysis-derived oils. These differences, while modest, exert a noticeable influence on fuel injection and atomization behavior. From an engine performance standpoint, the findings demonstrate that lower blend ratios, particularly B10 and B20, can be utilized without substantial degradation in efficiency. Brake thermal efficiency (BTE) for B10 remained within approximately 2% of diesel under full-load conditions, which suggests that minor substitution does not significantly disrupt combustion dynamics. However, as the proportion of WPB increased, a gradual decline in efficiency became evident. This trend appears to be closely linked to reduced atomization quality and delayed ignition, both of which contribute to incomplete combustion. Brake specific fuel consumption (BSFC) exhibited a corresponding increase with higher WPB content. This behavior can be attributed to the slightly lower calorific value of the fuel, which necessitates greater fuel input to achieve equivalent power output. In addition, combustion inefficiencies further amplify fuel consumption at higher blend levels. A particularly revealing observation is the nonlinear escalation of BSFC beyond the B20 blend, indicating that performance penalties become more pronounced at elevated concentrations of plastic-derived fuel. The emission analysis provides further insight into the combustion characteristics of WPB. Carbon monoxide (CO) and hydrocarbon (HC) emissions were consistently higher for WPB blends, reflecting incomplete oxidation of fuel molecules. This outcome is consistent with prior studies that associate higher viscosity and complex hydrocarbon structures with reduced combustion efficiency (Kalargaris et al., 2017, https://doi.org/10.1016/j.energy.2017.02.048). Conversely, nitrogen oxides (NOx) emissions exhibited an increasing trend with higher blend ratios, likely due to elevated in-cylinder temperatures and extended combustion duration. While this behavior aligns with conventional combustion theory, it highlights a critical environmental limitation of plastic-derived fuels. Taken together, these findings suggest that waste plastic biodiesel can serve as a supplementary fuel in diesel engines, particularly at lower blending ratios. The B10 blend, in particular, emerges as a viable option, offering near-diesel performance with only marginal increases in emissions. The B20 blend, while slightly less efficient, represents a practical compromise between fuel substitution and acceptable operational characteristics. Beyond this threshold, however, the adverse effects on performance and emissions become increasingly significant. It is worth emphasizing that the present study does not advocate for the complete replacement of diesel with plastic-derived fuels. Rather, it demonstrates the potential of partial substitution as a transitional strategy within a broader sustainable energy framework. By diverting plastic waste from landfills and converting it into usable energy, this approach contributes to both waste management and energy diversification. At the same time, the environmental implications associated with combustion emissions necessitate careful optimization and further technological refinement.

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