A COMPARATIVE ANALYSIS OF LIQUEFIED PETROLEUM GAS (LPG) AND COMPRESSED NATURAL GAS (CNG) AS ALTERNATIVE FUELS FOR INTERNAL COMBUSTION ENGINES

The global call for cleaner and more economical fuels has renewed interest in alternative fuels such as Liquefied Petroleum Gas (LPG) and Compressed Natural Gas (CNG). This study presents a comprehensive experimental comparison of LPG, Petrol (Gasoline), and CNG as fuels for internal combustion engines, focusing on combustion rate, energy efficiency, emissions, and cost effectiveness. Results showed that Petrol recorded the fastest combustion time (32 min/kg), followed by LPG (75 min/kg) and CNG (97 min/kg). Energy analysis revealed that although Petrol produced the highest instantaneous energy (1.45 MJ/min), its Relative Efficiency Index (REI) was lowest (0.69). Conversely, CNG achieved the highest REI (1.82), demonstrating superior long-term efficiency. Environmental measurements showed that CNG emitted the lowest pollutants CO (0.9 ppm), NO (0.79 ppm), and NO₂ (0.48 ppm) with no detectable SO₂ or H₂S. Economically, CNG emerged as the most cost-effective fuel at ₦20.83 per MJ, followed by LPG (₦22.00/MJ) and Petrol (₦27.64/MJ). Overall, CNG stands out as the cleanest, most sustainable, and most economical fuel alternative evaluated.