The paper presents a comparison of the fuel oil (FO) consumption and carbon dioxide (CO₂) emissions of a container ship’s 8000 twenty-foot equivalent unit (TEU) during oceanographic navigation. The evaluation has two types of FOs: a 3.4% heavy fuel oil with desulfurization (HFOWD) and a 0.5% very-low-sulfur fuel oil (VLSFO), based on the sulfur cap policy of the International Maritime Organization (IMO). The results show the average FO consumption at 130 tons/day of HFOWD and 141 tons/day of VLSFO, which means shifting to VLSFO increases fuel consumption 8.4% more than the HFOWD. The average CO₂ emissions are 429 tons/day of the HFOWD and 471 tons/day of the VLSFO, indicating an 9.5% increase in CO₂ emissions when the IMO adopts the low-sulfur fuel policy. Moreover, the VLSFO blending of various chemicals further deteriorates and wears out the main engine of the ship. IMO’s low-sulfur fuel policy significantly reduced the emission of sulfur oxides (SO_X) and particulate matter emissions. Still, we should not ignore the fact that adopting VLSFO may cause more CO₂ emissions. Therefore, while switching to low-sulfur fuels, the maritime industry should improve the related energy efficiency to reduce fuel consumption and CO₂ emissions.

This study developed and examined the application of bismuth sulfide doped on graphitic carbon nitride (Bi₂S₃@g-C₃N₄) in the degradation of NO under solar irradiation. Bi₂S₃@g-C₃N₄ was prepared through the calcination method. The morphological structure and chemical properties of the synthesized photocatalyst were analyzed before the degradation tests. After doping with Bi₂S₃@g-C₃N₄, the bandgap was reduced to 2.76 eV, which increased the absorption of solar light. As a result, the Bi₂S₃@g-C₃N₄ achieved higher NO degradation (55%) compared to pure Bi₂S₃ (35%) and g-C₃N₄ (45%). The trapping test revealed that the electrons were the primary species responsible for most of the NO degradation. The photocatalyst was stable under repeated solar irradiation, maintaining degradation efficiencies of 50% after five consecutive recycling tests. The present work offers strong evidence that Bi₂S₃@g-C₃N₄ is a stable and efficient catalyst for the photocatalytic oxidation of NO over solar irradiation.