VLSFO associated with higher black carbon emissions than HFO

VLSFO associated with higher black carbon emissions than HFO

Three weeks after the International Maritime Organization’s (IMO’s) global regulation on sulphur content in fuel oil entered into force, new figures indicate that very low sulphur fuel oil (VLSFO) compliant with the new regulation, is just as detrimental to the environment as conventional heavy fuel oil (HFO).

Figures submitted by Finland and Germany to the IMO suggest that new fuel blends with sulphur content less than 0.5 per cent can contain a large percentage of aromatic compounds, which have a direct impact on Black Carbon (BC) emissions.

The study examined the impact of different hybrid fuel oil qualities on BC emissions and compared these with traditional HFO and marine gas oil (MGO, also known as DMA) grade fuels and a possible future synthetic Gas to Liquid (GtL) fuel, at varying engine ratings on a test bed. All tests were performed with the same lube oil. The tested 0.5 per cent sulphur fuels were ordered as possible sample mixtures from refinery-streams most likely to be used in 2020. A high aromatic content in future low sulphur marine fuels after 2020 is expected.

The study found that the combustion of fuels with higher aromatic content emits higher concentrations of BC. New hybrid fuels with 0.5 per cent sulphur content used in the study contained a high proportion of aromatic compounds in a range of 70 per cent to 95 per cent, which resulted in increased BC emissions in a range of 10 per cent to 85 per cent compared to HFO and in a range of 67 per cent to 145 per cent compared to DMA.

The study concludes that: “It is necessary to implement aromatic content, or H/C ratio, in the specification of marine fuels of the ISO 8217 petroleum standard. This would enable a better qualification of marine fuels with respect to their environmental performance in terms of BC emissions and benefit their characterisation for ignition and combustion quality. It is suggested that the International Organisation for Standardisation review ISO 8217 to include specifications taking into account these results.”