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Study Says Scrubbers have a lower climate impact than low-sulphur fuels

The CO2-emissions associated using an Exhaust Gas Cleaning System (EGCS, or scrubber) vary between 1.5% and 3% for a number of representative ships. In many cases, the emissions caused by producing low-sulphur fuels for these ships are higher, depending on the quality of the low-sulphur fuel, the refinery and the crude oil slate. This is the main conclusion from the new study ‘Comparison of CO2 emissions of MARPOL Annex VI compliance options in 2020’ issued by CE Delft.

MARPOL sets limits for the sulphur content of fuel oil. As of January 1st, 2020, the sulphur content of fuel oils used outside Emissions Control Areas (ECAs) is 0.50% m/m. Inside ECAs, the limit has been 0.10% m/m since 2015.

In practice, there are two options to comply with the MARPOL Annex VI Regulation 14:

1. using an EGCS in combination with fuel oils with a sulphur content that is higher than 0.50% or 0.10%; and;

2. using fuel oil with a sulphur content of 0.50% (VLSFO), respectively 0.10% or less (ULSFO).

Both options result in an increase of well-to-wake CO2 emissions:

1. an EGCS requires energy which is generated by engines running on fuel oil and thus generate CO2. In addition there are emissions associated with manufacturing scrubbers and emissions from the seawater;

2. desulphurisation in a refinery requires hydrogen which is generally produced from methane, emitting CO2 in the process, as well as energy.

This report quantifies and compares the CO2 footprint of both options. The use of an EGCS results in an increase of CO2 emissions between 1.5% and 3% for a range of representative ships. Desulphurisation inevitably leads to an improvement of the fuel quality in terms of aromatics content and viscosity. 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.

Jasper Faber: “This study provides a comprehensive overview of the climate impacts of different options to reduce sulphur emissions. It shows that in many cases, the carbon footprint of using a scrubber is lower than low-sulphur fuels.”

The study has been commissioned by three major EGCS suppliers.
Source: CE Delft

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