Comparative Analysis of Diesel and Liquefied Natural Gas (LNG) as Marine Fuels
Abstract
In support of the decarbonization goals of international shipping, this study compares the technical performance, economic viability, and environmental impacts of diesel- and liquefied natural gas (LNG)-powered marine engines. A mixed-methods approach was adopted, combining quantitative modeling using MATLAB and Excel with qualitative analysis of seven expert interviews using NVivo. Data were obtained from technical manuals, academic literature, industry reports, and regulatory documents. Key performance indicators included thermal efficiency, specific fuel consumption (SFC), lifecycle emissions, retrofit cost, and payback period. Monte Carlo simulations (n = 10,000) were employed to address uncertainty in economic and environmental assessments. Results indicate that LNG engines outperform diesel engines in technical efficiency, achieving a thermal efficiency of 46.5% compared to 43.5% and a lower SFC of 165 g/kWh versus 185 g/kWh. Environmentally, LNG virtually eliminates sulfur oxides (SOx) and particulate matter (PM) emissions while reducing carbon dioxide (CO₂) emissions by approximately 22–25%, ensuring compliance with IMO 2020 sulfur regulations. However, methane slip (≈14 g/kWh) remains a significant challenge, potentially reducing LNG’s greenhouse gas advantage by up to 40% under high-slip conditions. Economically, LNG engines incur higher capital and retrofit costs (approximately US$11 million compared to US$7 million for diesel) but benefit from lower annual fuel and maintenance expenses. LNG payback periods range from 6–9 years, compared with 3–5 years for diesel. Sensitivity analysis shows that higher carbon taxes and wider fuel price differentials improve LNG competitiveness. Expert interviews further highlighted LNG’s role in regulatory compliance and sustainability while identifying methane regulation gaps and infrastructure limitations in developing countries. The study concludes that LNG is an effective transitional fuel toward net-zero shipping, provided methane slip and infrastructure challenges are addressed. The findings offer valuable insights for policymakers, investors, and shipowners navigating maritime decarbonization.