Optimizing Biodiesel-Butanol Blends for Low CO₂ Emissions and Fuel Efficiency in Diesel Engines

Abstract

This study investigates the impact of various biodiesel–butanol fuel blends on CO₂ emissions and brake-specific fuel consumption (BSFC) under different engine speeds and load conditions. Experiments were conducted using blends of biodiesel (B5, B10, B15) combined with butanol concentrations of 5% and 10% (Bu5, Bu10) at engine speeds of 1200, 1800, and 2400 rpm, across load levels of 25%, 50%, and 75%. The results indicate that both CO₂ emissions and BSFC are significantly influenced by fuel composition, engine load, and speed. Notably, blends such as B5Bu5 and B10Bu5 showed the lowest CO₂ emissions at high engine loads, reaching values as low as 0.2% at 75% load and 1200 rpm, suggesting enhanced combustion efficiency. At higher engine speeds, CO₂ emissions increased, especially at mid-load conditions, with B10Bu10 recording a peak emission of 4.2% at 2400 rpm and 50% load. Regarding BSFC, the B15Bu10 blend consistently demonstrated superior fuel efficiency, especially under full-load conditions, with the lowest recorded BSFC of 165 g/kWh at 25% load and 1200 rpm. Conversely, blends with excessive butanol content exhibited higher BSFC at low loads, indicating incomplete combustion. These findings highlight the importance of optimizing biodiesel–butanol ratios based on specific engine operating conditions. The study contributes valuable insights into cleaner alternative fuels, supporting efforts to reduce carbon emissions and improve energy efficiency in diesel engine systems.