Policy initiatives > Air pollution from ships > IMO MARPOL Convention

IMO MARPOL Convention

The International Maritime Organization is a UN body for international shipping.

International shipping represents a substantial and growing source of emissions of air pollutants, including greenhouse gases. Emissions of air pollutants from international shipping are regulated by Annex VI to the International Convention on the Prevention of Pollution from Ships (MARPOL), which was originally signed in September 1997 and came into force in May 2005. Annex VI sets limits on the sulphur content of marine fuel oils and on the emissions of nitrogen oxides (NOx) from new ship engines.

However, the 1997 standards are so weak as to be hardly likely to have any appreciable effect, and on 9 October 2008 the IMO's Marine Environment Protection Committee (MEPC) agreed to revise and strengthen the emission standards in Annex VI. The revised law entered into force on 1 July 2010.

New sulphur limits
The current global limit on sulphur in marine fuels is 4.5 per cent. Under the revised Annex this limit will fall in two stages to 3.50 per cent in 2012, and finally to 0.50 per cent in 2020 (subject to a review in 2018). As an alternative to use low-sulphur fuels, ships are allowed to use exhaust gas cleaning systems (e.g. scrubbers) or use other methods to limit their sulphur emissions.

Emissions Control Areas
An application for designating a sea area as an Emission Control Area (ECA) must be approved by the Parties to Annex VI. ECAs may be designated for sulphur oxides (SOx) and particulate matter (PM), or nitrogen oxides (NOx), or all three types of emissions, subject to a proposal from an IMO member country.

Annex VI originally set a limit of 1.50 per cent sulphur for marine fuel oil used by ships sailing in designated Sulphur Emission Control Areas (SECAs). The revised Annex VI lowered the sulphur limit in SECAs to 1.00 per cent from July 2010 and to 0.10 per cent as from 2015.

The Baltic Sea was the first SECA to enter into force in 2006, followed by the North Sea in 2007.

In March 2010, the IMO officially designated waters extending 200 nautical miles (370 kilometres) from the coast of the United States and Canada as the first “full” ECA, i.e. covering SOx, PM and NOx. Entry into force will be 1 August 2011, which means that the stricter sulphur limits take effect from 1 August 2012.

Figure 1: Comparison of various fuel sulphur limits in parts per million (ppm). Please note that the upper figure of 45 000 ppm corresponds to 4.5% sulphur content, whereas the lower figure of 10 ppm for road transport fuels corresponds to a 0.00001% suphur content.
[Click on image to enlarge]

NOx emission standards
Emissions of NOx are controlled by emission standards for new ship engines. The Tier I standards apply to all new engines as from January 2000, but these are so weak that in practise they do not have any appreciable effect. The revised Annex sets new Tier II standards that apply from 2011 and will cut emission by 16-22 per cent (relative to Tier I). It also sets Tier III standards that will cut emissions from new engines by about 80 per cent (relative to Tier I), but the Tier III standards will apply only in the specially designated NOx emission control areas (NECAs).

Figure 2: MARPOL Annex VI NOx Emission Limits. For comparison, EU truck emission standards are set at 2 g/kWh from 2009, and at 0.4 g/kWh from 2013.
[Click on image to enlarge]

GHG emissions
The IMO has been considering how to reduce greenhouse gas (GHG) emissions from shipping since before 2000, when it received a report estimating those emissions and describing various potential measures to reduce them. So far, however, the IMO has failed to make any significant progress in talks on addressing GHG emissions from shipping. Progress has been thwarted mainly by the opposition of developing countries (non-Annex I countries under the Kyoto Protocol) to any IMO initiative on climate change that fails to respect the principle of "common but differentiated responsibilities".

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