Experimental evaluation of nanobiochar and metallic oxide nanoparticles with Croton macrostachyus seed oil biodiesel on combustion and emission characteristics

Biomass-derived nanoparticles offer a safer alternative to metallic oxides, yet their use in diesel–biodiesel blends remains limited. This study explores the catalytic effect of corn stover–derived nanobiochar (NBC) on the performance, combustion, and emissions of Croton macrostachyus (CMS) biodiesel, compared with Al₂O₃ and TiO₂ nanoparticles, at 2700 RPM and 0–80% load. The novelty lies in revealing NBC’s influence on CP, apparent HRR, and ID period in CMS biodiesel blends. Experiments were conducted using six fuel blends: B20 (20% CMS biodiesel + 80% diesel), B20NBC30, B20NBC50, B20NBC75 (with 30, 50, and 75 ppm NBC, respectively), B20A50 (with 50 ppm Al₂O₃), and B20T50 (with 50 ppm TiO₂). The result shows that the NBC additive reduced the NOx, CO, and HC emissions by up to 9.8%, 8.4%, and 27.3% respectively, and BSFC by 2.2% and increased BTE by 2.6% compared to the B20. Conversely, TiO₂ and Al₂O₃ were more effective in reducing HC emissions, achieving reductions of 45.9% and 29.5% respectively, while reducing BSFC and increasing BTE compared to NBC additive. In addition, B20NBC50 exhibited an average reduction in cylinder pressure (CP) of 0.5%, heat release rate (HRR) of 517.51 J/ o CA with a 2.7% increment and the shortest ignition delay (ID) and advanced start of combustion (SoC) compared to the B20, B20NBC30, and B20NBC75, that makes NBC at 50 ppm as the optimum concentration. NBC reduced NOx due to its higher specific heat capacity, while Al₂O₃ and TiO₂ increased it, demonstrating NBC’s advantage and potential as a sustainable, biomass-derived alternative to metallic nanoparticles.