Comparison of CO2 emissions of MARPOL Annex VI compliance options in 2020

MARPOL, the main international convention preventing pollution from ocean-going vessels, sets limits on the sulphur content of the fuel oil they burn. Under Regulation 14 of MARPOL Annex VI, as of January 1st, 2020 the maximum permitted 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 for compliance with this regulation:

  1. using an Exhaust Gas Cleaning System (EGCS) in combination with fuel oils with a sulphur content over 0.50% or 0.10%, respectively
  2. using fuel oil with a maximum sulphur content of 0.50% (VLSFO) or 0.10% (ULSFO).

This report, commissioned by three major EGCS suppliers, quantifies and compares the carbon footprint of the two options.

For the first option, use of an EGCS, It is found that this results in a 1.5-3% increase of CO2 emissions for a range of representative ships. This is because an EGCS needs to be powered by an engine running on fuel oil and thus emitting CO2. In addition, there are emissions associated with scrubber manufacture as well as emissions from the seawater.

While desulphurisation in a refinery inevitably leads to improved fuel quality in terms of aromatics content and viscosity, the desulphurisation process itself increases CO2 emissions by over 1% and often a multiple of that figure, depending on the degree of fuel quality improvement, refinery layout and the crude used. In addition, the process requires hydrogen, which is generally produced from methane, emitting CO2 in the process, on top of the emissions due to energy use.

The conclusion of this study is therefore that well-to-wake CO2 emissions increase in both options.

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