Pyrolysis Oil Extraction from E-Waste Plastics: Characterization and Comparative Analysis with Diesel Fuel

Abstract

The increasing accumulation of electronic waste (e-waste) presents both environmental and energy challenges, necessitating innovative strategies for resource recovery and sustainable fuel production. This study investigates the catalytic pyrolysis of e-waste plastics to produce pyrolysis oil (PPO) and evaluates its potential as an alternative to diesel fuel. The pyrolysis process demonstrated a high conversion efficiency of 99%, yielding 88.12% PPO, 11.23% non-condensable gases, and 0.645% solid residue, showcasing its effectiveness in extracting valuable fuel from e-waste plastics. The fuel properties of PPO, including density (1080–1070 kg/m³), calorific value (39 861–43 154 kJ/kg), flash point (35–50°C), and cetane number (50 for raw PPO), were analyzed and compared with diesel. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the presence of alkanes, alkenes, and oxygenated compounds, influencing fuel behavior. While PPO exhibited higher energy content, challenges such as lower cetane number, higher sulfur content (0.35%), and low flash points necessitate further refinement for broader diesel engine applications. To evaluate its real-world performance, PPO-diesel blends (25 to 100%) were tested in a four-cylinder turbocharged diesel engine under varying loads. Combustion analysis revealed extended ignition delays and higher peak pressures for blends with increased PPOcontent due to its higher aromatic concentration. Heat release rates (HRR) were significantly elevated, enhancing fuel-air mixing but causing combustion instability at low loads. At full engine load (100%), PPO exhibited a delayed but stable combustion process, achieving a brake thermal efficiency (BTE) of 34%, close to diesel’s 38% efficiency. However, at low engine loads, blends above 90% PPO exhibited incomplete combustion and operational inefficiencies. Emission analysis indicated a significant increase in NOx emissions with rising PPO content due to higher in-cylinder temperatures and prolonged premixed combustion phases. Additionally, carbon monoxide (CO) and unburned hydrocarbons (UHC) emissions were higher at low engine loads, while carbon dioxide (CO₂) emissions increased linearly due to PPO higher carbon-to-hydrogen ratio. Despite higher NOx emissions, PPO blends showed reduced particulate matter (PM) emissions due to lower soot formation. Despite these challenges, PPO blends containing 60–70% PPO at 80–90% engine loads demonstrated optimal performance, making them suitable for selective applications. Further research should focus on cetane number enhancement, desulfurization techniques, and fuel injection optimization to improve low-load stability and emissions control. This study highlights the potential of e-waste plastics as a renewable energy source, contributing to sustainable waste management, circular economy initiatives, and energy security while reducing reliance on fossil fuels.