Black carbon emissions from bunker fuels may be damaging the environment in the Arctic. File Image / Pixabay
An additive company director has suggested paraffinic components within very low sulfur fuel oil (VLSFO) -- rather than aromatic ones -- may be behind complaints of higher black carbon emissions from the new fuels.
Earlier this year environmental groups suggested that some VLSFO blends were causing high black carbon emissions, which would have a detrimental effect on the environment in regions like the Arctic, as well as being harmful to human respiratory health.
The bunker industry in general pushed back against these claims, saying it was possible that the more aromatic VLSFO types might have high black carbon emissions, but that the more common ones towards the paraffinic end of the scale would not.
Francisco Malta, a director at Aderco distributor VM Industrials, suggests the opposite.
"Believe it or not, today, paraffinic hydrocarbons in VLSFOs could actually be the reason for black carbon emission," Malta wrote in a LinkedIn post this week.
High levels of blending of VLSFO to maximise profit margins may be causing less stable molecules to be found in the paraffinic blends, he said, causing higher black carbon emissions when the fuels are burned.
Some of the blending components being used for VLSFO have not been sufficiently hydrotreated during the refining process, Malta argued.
"In a controlled environment; the fractioned chains are hydrogenated, this means adding the missing hydrogen molecules to avoid the double-bond effect," he said.
"Unfortunately, when blending batches from many different refineries and sources this process is no longer taking place on every batch.
"As this is at such a molecular level and does not change the fuel specification, the batches with a shortage in hydrogens are not even identifiable."
These unstable hydrocarbons agglomerate with water droplets and other hydrocarbons when the fuel containing them is burned, resulting in higher black carbon emissions. This effect tends not to happen as severely in aromatic fuel blends as the unstable hydrocarbons more often combine with asphaltenes and drop out of suspension to form sludge.
Malta said similar problems had been found in the automotive s industry with diesel before, and that the solution would be found in fuel additives that either improve combustion properties or neutralise the unstable hydrocarbons.
"Blending is here to stay; there is no turning back, 'that ship has sailed', Malta said.
"Blending is the only economical method to produce low-sulphur fuels, and just as the automotive industry found, the shipping industry will not be able to operate without excessive black carbon emissions if fuel stability is not addressed.
"Thanks to the automotive industry, the advantage of shipping is that we may know the why and how to fix it."