Reduction of Sulfur Content in Marine Fuel Oil through Biodiesel Blending

Marine fuel oils derived from crude‑oil residues typically contain high sulfur concentrations, leading to significant SO₂ emissions during combustion and contributing to acidification and atmospheric pollution. The implementation of the IMO 2020 regulation, which limits sulfur content in marine fuels to 0.5% m/m, has intensified the need for practical, low‑cost desulfurization strategies. This study investigates the effectiveness of biodiesel blending as a first‑stage method for reducing sulfur concentration in heavy marine fuel oil. Experimental mixtures were prepared by blending a high‑sulfur residual fuel (32,590 ppmwt S) with biodiesel at volumetric ratios of 10%, 15%, and 20%. Sulfur content was measured using Energy‑Dispersive X‑Ray Fluorescence Spectroscopy (ASTM D4294). Results show a substantial reduction in sulfur concentration, decreasing to 12,990 ppmwt (10% blend), 12,930 ppmwt (15% blend), and 12,540 ppmwt (20% blend). Although the reduction trend is nearly linear, the achieved sulfur levels remain above the IMO 2020 limit, indicating that biodiesel blending alone cannot ensure regulatory compliance. Nevertheless, the findings demonstrate that biodiesel acts as an effective diluent due to its extremely low sulfur content (0.9 mg/kg), while simultaneously improving fuel properties such as flash point, lubricity, and combustion behavior. This work represents the first phase of a broader research effort aimed at developing a multi‑stage desulfurization strategy. Future work will explore higher biodiesel ratios, catalytic or chemical desulfurization methods, and hybrid approaches combining blending with exhaust‑gas cleaning technologies.