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A new study published by CE Delft has found that CO2 emissions associated with using scrubbers ‘vary between 1.5% and 3%’ for a number of ships while ‘in many cases, the emissions caused by producing low-sulphur fuels for these ships are higher’.

The study, Comparison of CO2 emissions of MARPOL Annex VI compliance options in 2020, was commissioned by Alfa Laval, in cooperation with Yara Marine and Wärtsilä.

The study noted that burning very low sulphur fuel oil (VLSFO) and using exhaust gas cleaning systems (EGCS) result in an increase of well-to-wake CO2 emissions – but that the latter could be less carbon-intensive.

While desulphurisation ‘inevitably leads to an improvement of the fuel quality in terms of aromatics content and viscosity’, the study found that the increase of emissions associated with desulphurisation in a refinery are ‘higher than 1% and in many cases multiple times higher, depending on the quality improvement of the fuel, the refinery layout and the crude used.’

The study found that: ‘Various processes can be used to produce low-sulphur fuels; the choice will depend on the refinery design and the crude oil slate the refinery uses. In most cases, sulphur removal coincides with an improvement of quality of the fuel, as unsaturated bonds and aromatics are saturated and the fuel becomes more paraffinic. Many low-sulphur fuels have better qualities in terms of viscosity and aromatics content than required by the applicable standards.

‘Whether or not removal of sulphur on board or removal of sulphur in the refinery generates lower CO2 emissions depends on whether or not the inevitable fuel quality improvements are taken into account. The mere removal of sulphur generates less CO2 emissions than the use of an EGCS, whereas sulphur removal plus fuel quality improvement has more CO2 emissions than using an EGCS.’

According to CE Delft, the finding of its study is similar to other studies.

As Bunkerspot previously reported, a study undertaken by the IVL Swedish Environmental Research Institute on exhaust gas cleaning systems concluded that ‘the effluent waters from scrubber systems are an environmental risk’, and ‘these effluents are avoided by the use of the low sulphur oil’.

Referencing the IVL study, CE Delft said: ‘The main difference between this study and the study from IVL is the fact that this study has used multiple reference ships and data about the EGCSs received from manufacturers, which they would have installed on the selected reference ships, whereas the study from IVL has used generalised assumptions about the required power to operate an EGCS. IVL assumes an additional power use of 1.3%.’

CE Delft also highlighted the finding of a study carried out by researchers at the Chalmers University of Technology in Sweden in 2011.

The Chalmers study, said CE Delft, ‘found that the CO2 emissions of ships using an EGCS or using low-sulphur fuels are very close, but they assume a much lower power consumption by the EGCS: 1% of the fuel used.’

The study can viewed in full here.

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