Air pollution from ships:
Needing attention

Factsheet from the Swedish NGO Secretariat on Acid Rain. May 2003.

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Emissions
A great part of the pollutants that get spread out in the air over land in Europe comes from ships in nearby waters. There are however technical means that would enable them to be cut by as much as 80-90 per cent, and very cost-effectively compared with what would have to be done to achieve similar results ashore. Reductions of this magnitude will be needed if the EU's environmental and health objectives are to be attained, and maritime transport is to become a more sustainable mode.

The emissions of air pollutants from ships engaged in international trade in the seas surrounding Europe - the Baltic, the North Sea, the north-eastern part of the Atlantic, the Mediterranean, and the Black Sea - were estimated to have been 2.6 million tons of sulphur dioxide and 3.6 million tons of nitrogen oxides (expressed as NO₂) a year in 2000 (see Table 1, below.)

While pollutant emissions from land-based sources are gradually coming down, those from shipping show a continuous increase. In consequence, when the fifteen EU member countries have fulfilled their commitments in accordance with the directive on national emission ceilings, and assuming that the growth in emissions from shipping stays at 1.5 per cent per year, by 2010 ships' emissions will equal three-quarters of the EU total for sulphur and nearly two-thirds of that for nitrogen oxides (see table).

Table 1. Emissions of sulphur dioxide (SO₂) and nitrogen oxides (NOx) in 1990, 2000 and 2010 (million tons).

¹ Projection according to the EU directive on national emission ceilings.
² Assuming an annual growth of between 1.5 and 3 per cent.

Sources: Entec (2002) for ships' emissions and UN ECE (2002) for land-based emissions.

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Health and environmental problems
Sulphur and nitrogen oxides can become converted into sulphate and nitrate particles, which are very small and among the more frequent of airborne particles. Exposure to fine particles can cause cardiovascular and chronic pulmonary disease, including lung cancer. It has been estimated that ship emissions contribute between 20 and 30 per cent to the concentrations of secondary inorganic particles in the air in most coastal areas.

Nitrogen oxides also contribute to the formation of ground-level ozone, which damages vegetation as well as human health. Especially in the Mediterranean region, ship emissions contribute notably to increased levels of ground-level ozone.

Although most of the SO₂ and NOx emitted from ships plying in international trade gets deposited over the sea, shipping is a major source of acidifying and eutrophying fallout over the land in many countries. In Denmark, the Netherlands, Sweden, Norway, and Estonia, ships' emissions stand for 10 per cent or more to the depositions of sulphur. Similarly, in Denmark, Estonia, Sweden, Greece, Portugal, the Netherlands, Finland, and Ireland, well over 10 per cent of the total deposition of oxidized nitrogen compounds comes from ships.

Air pollutants, such as SO₂, NOx, and ozone, accelerate the rate of deterioration of a large number of various materials. Buildings and monuments made of limestone and some kinds of sandstone are especially sensitive to attack from acidic substances.

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International action so far
Although some countries, such as Sweden and Norway, have taken steps to attack the problem of ships' emissions independently, on the whole little has been done about it.

Shipping being largely an international business, it would be logical to try and bring about global agreement for control of its emissions, and an attempt has been made in the UN International Maritime Organization (IMO). After years of negotiation, agreement was reached in 1997 on an air-pollution annex to the MARPOL 73/78 Convention. But this agreement was so weak that it was obvious it would have little effect. Annex VI establishes a global sulphur cap of 4.5 per cent for bunker fuel, as well as designating two so-called sulphur emission control areas (the Baltic Sea and the North Sea), where the sulphur content of fuel used by ships must be below 1.5 per cent. It also prescribes emission standards for NOx for diesel engines with a power output greater than 130 kW, but these standards are so weak that virtually all new engines can already comply.

Entry into force of Annex VI requires ratification by at least 15 countries representing 50 per cent of the gross tonnage of the world's merchant fleet. To date (May 2003) only six countries have ratified - Norway, Sweden, Bahamas, Singapore, Liberia, and the Marshall Islands - together representing approximately one-quarter of world tonnage. The voting rules of the MARPOL convention, as well as experience to date, make it unlikely that possible further moves by the IMO will result in any significant emission reductions in the near future.

Protocols for reducing emissions under the Convention on Long-range Transboundary Air Pollution do not cover those from international shipping. Moreover, the emissions of greenhouse gases from such shipping are not covered by the Framework Convention on Climate Change or its Kyoto protocol.

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Lower-sulphur fuel
Emissions of SO₂ are directly proportional to the sulphur content of the fuel. The simplest and least expensive way of reducing them is to go over to using fuel oil with a low sulphur content. The average sulphur content of marine heavy fuel oil (so-called bunker fuel) is now around 3 per cent, but low-sulphur oils can also be had. They usually require no engine modification, and the additional cost is to some extent compensated by various savings. Because of its higher quality, low-sulphur fuel oil has the advantage of resulting in less wear on the machinery, with less need too for lubricating oil and less maintenance work, thus making for smoother engine running, with less risk of operating problems. High-sulphur marine heavy fuel oil costs around $100-130 per ton, while marine gas oils cost around $150-190 per ton.

The price differential between low-sulphur bunker fuel - with a sulphur content of 1 per cent or less - and a high-sulphur type (3.5%) averaged around $19 per ton 1990-2001. The price differential for the low-sulphur bunker fuel as resulting from new investment in desulphurization at the refineries was estimated by the Commission's consultant Beicip-Franlab to lie between 50-90 euros per ton. (See also section on cost-effectiveness, below.)

A system with fairway and harbour dues differentiated for environmental effect was introduced in Sweden in January 1998. Here shipowners who state and verify that they are using fuel oil with a sulphur content of less than 0.5 per cent for ferries and 1.0 per cent for cargo vessels get a discount on the due. A rapid increase in the number of ships operating on low-sulphur oil, spurred to some extent by the demands for environmentally friendly transport from some of the big shippers, has come about since 1998, and close on 80 per cent of the entries to Swedish ports are now of ships using low-sulphur fuel.

For comparison, SO₂ emissions from land-based stationary sources are regulated in the EU by several directives. Directive 1999/32 stipulates that the maximum allowed emissions from all oil-fired plants must not exceed the equivalent of using heavy fuel oil with a sulphur content of 1 per cent. For gas oils, including those for marine use, the limit is set stricter, at a maximum of 0.2 per cent, and it will be further reduced to 0.1 per cent as from January 2008. Any new large combustion plants (i.e. with a thermal capacity of more than 50 MW) built after 2003 must, according to directive 2001/80, keep their SO2 emissions below levels equivalent to maximum sulphur contents in fuel oil of 0.1 to 0.5 per cent. The bigger the plant, the stricter the emission limit value that will apply.

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Reducing emissions of NOx
Water injection and water emulsion. Water is injected into the combustion chamber or mixed with the fuel in order to lower the temperature of combustion and hence reduce NOx formation. The potential for emission reduction is at most around 50 per cent, but at the cost of increased fuel consumption. The installation cost is however lower than for either of the following methods.

HAM, Humid Air Motor, is a technique for preventing the formation of NOx during combustion by adding water vapour to the combustion air. Performance is unaffected either by the quality of the bunker oil or by engine workload. By reducing the consumption of fuel and lubricating oil, HAM has the advantage over SCR of somewhat lowering operating costs instead of increasing them. The method is able to reduce NOx by 70-80 per cent at a cost apparently similar to that of SCR.

Selective Catalytic Reduction, SCR, is a system for after-treatment of the exhaust gases. It can reduce the emissions of NOx by more than 90 per cent, but may require low-sulphur bunker oil. When retro-fitted it replaces the exhaust silencers. Nitrogen oxides are reduced to nitrogen gas by spraying urea or ammonia into the gases before they pass through a catalytic converter. Reduction costs are generally below 600 euros per ton of NOx, or lower if the equipment can be installed while the ship is being built. There are now more than fifty ships fitted for SCR. About half of them are Swedish, and most of the others are frequent callers at Swedish ports. This is largely a result of the environmentally differentiated fairway and port dues that have been in use in Sweden since 1998.

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Cost-effective to do it at sea
The costs of typical measures for reducing ships' emissions of sulphur dioxide range from 250 to 600 euros per ton, and for nitrogen oxides from 350 to 600 euros per ton. The measures required for reducing the emissions from sources on land more than envisaged by current legislation would usually cost still more, and in some cases much more. A main reason for the costs at sea generally being lower is that the easiest and least expensive measures have already been taken ashore in most EU countries, but not yet at sea.

The cost-effectiveness of abatement at sea was studied while examining the EU strategy for combating acidification. It appeared that if the interim target for environmental quality proposed for the EU were to be attained solely by the use of technical measures on land, by 2010 the annual cost would be around 7 billion euros. The overall cost could however be brought down by 2.1 billion euros, or about 30 per cent, if cost-effective measures to limit the emissions of SO2 and NOx from ships were applied in the Baltic, North Sea, and waters of the north-eastern Atlantic.

With measures for shipping added to those for land-based sources, the environmental target could thus be attained at a considerably reduced cost. Alternatively, still more could be achieved at the same cost.

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An EU strategy to reduce air pollution from ships
The EU strategy to reduce the emissions of air pollutants from sea-going ships was adopted by the Commission in November 2002. It contains a broad series of objectives, proposed actions and recommendations for bringing about such reductions over the next 5-10 years. The strategy document includes a list of actions that the Commission itself intends to take, as well as those it recommends to other parties. Here are some examples:

International action. Within the IMO the Commission will continue to press for tougher measures to reduce ships' emissions. It recommends member states to ratify MARPOL Annex VI as soon as possible.

EU regulation of emission standards. Also in November 2002, the Commission published a proposal to amend directive 1999/32 so as to limit the sulphur content of marine fuels marketed and used in the EU (see more below). It has moreover put forward a proposal to amend directive 1997/68 on NOx and PM emission standards for non-road engines, the aim being among others to extent its scope so as to make it include engines for use aboard vessels operating on inland waterways.

EU regulation on economic instruments. This year the Commission will be proposing the development of an EU system of differentiated infrastructure charges for all modes of transportation. Maritime transportation would be part of that framework.

Voluntary measures. The Commission urges the international bunker industry to make available significant quantities of marine fuel oil with a maximum sulphur content of 1.5 per cent, so as to be able to supply ships destined for a sulphur emission-control area. It also urges port authorities to consider introducing voluntary speed reductions, and to require, facilitate, or provide incentives for ships to use land-based electricity or clean onboard power while in port.

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Proposal to limit the sulphur content of marine fuels
As part of its strategy to reduce the atmospheric emissions from seagoing ships, the Commission has published a proposal for modifying directive 1999/32. The aim of the proposal is to reduce the emissions of SO2 and particulates, thus lowering the extent to which ships contribute to problems of air quality and acidification. The main items are to:

• Introduce a 1.5-per-cent sulphur limit on marine fuels used by all seagoing vessels in the Baltic, the North Sea, and the English Channel, in line with the sulphur limits of MARPOL Annex VI. This internationally agreed limit is intended to be implemented 12 months after the entry into force of the revised directive, or one year after that of Annex VI, whichever should be the earlier.
• Introduce a 1.5-per-cent sulphur limit on marine fuels used by passenger vessels in regular service to or from any EU port. To ease the effect on operators, it is proposed to allow a transition period ending July 2007.
• Amend the existing provisions for lighter marine fuels (so-called distillates) used by sea-going and inland vessels by introducing an 0.2-per-cent sulphur limit on fuel used by ships at berth in ports. It is suggested firstly to ban the sale of marine gas oils with more than 0.2 per cent sulphur, secondly to remove the 0.2-per-cent sulphur limit on marine diesel oil, and then ban the sale of such fuels with more than 1.5 per cent sulphur.

By employing the higher estimate of 50 euros per ton as the incremental cost for low sulphur bunker fuel, the Commission estimated that the combined costs, when all these measures have to be implemented (by 2006-08), will amount to about 1.1 billion euros a year. Taken together, by 2008 the proposed measures are expected to reduce the annual emissions of SO2 from shipping by about 10 per cent, compared with the level of emissions in 2000. The improvement in fuel quality will also result in lowered emissions of particles and nitrogen oxides.

According to the Commission's analysis, only some of the benefits of reduced emissions can be expressed in terms of money. Methodologies are as yet unavailable for monetizing for instance the effects on ecosystems of exceeding the critical loads for acidification, but where the benefits have been estimated, the Commission has taken into account the effects on human health as well as on crops and modern building materials. Added up, they are estimated to amount to 2.7 billion euros a year. It is in any case clear from the analyses that the benefits will significantly outweigh the costs in all aspects.

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What the EU and its member states should do
Four environmentalist organizations - the European Environmental Bureau, European Federation for Transport and Environment, Seas At Risk, and the Swedish NGO Secretariat on Acid Rain - have worked out a series of proposed guidelines for action.

• The best approach would be to combine regulation with market-based instruments.
• The EU should introduce legislation for reducing emissions of SO₂ from ships, either by setting limits to the sulphur content of fuel used by ships in the Exclusive Economic Zones (or at least in the various countries' territorial waters), or on the sulphur content of fuel for marine use sold in EU ports, or both. The maximum permitted sulphur content for bunker fuel should initially be set at 0.5 per cent, and should be applied in all Community sea areas as from 2005. This would reduce the annual emissions of SO₂ from ships by about 80 per cent, as compared with those in 2000.
• Charges differentiated according to environmental effect should be imposed, and apply impartially to all vessels. These charges should be related to the amounts of pollutants emitted, and set so as to make it financially worthwhile - at least for ships that regularly frequent the area - to use fuels with a lower sulphur content and to invest in the necessary techniques for ensuring a distinct reduction of NOx emissions.
• The EU and its member states should make every effort to ensure the early entry into force and subsequent implementation of Annex VI to the MARPOL Convention, and strive to markedly strengthen the weak emission standards it sets for NOx, as well as the standards for a maximum allowed sulphur content of bunker fuels. Moreover, the EU should introduce stricter NOx emission standards than those of Annex VI.
• Measures should also be introduced for control of emissions in inland waterways.
• Any measure needs to be accompanied by a monitoring of compliance, not only by seagoing vessels, but also by bunker fuel trading boats and at onshore selling points.

Some economic incitements, such as environmentally differentiated fairway and port dues, have the advantage of being capable not only of rapid introduction but also of yielding quick results - as can also EU legislation, although in that case it may take two years or so to reach the necessary political agreement. The development and introduction of more elaborate economic instruments, such as infrastructure charges, is likely to need even more time. Global agreements depending on the IMO have also been shown to require a relatively long time to arrive at, and then still more before they can be ratified and come into force.

Some measures, such as lowering the sulphur content of fuels and retrofitting SCR or HAM, will bring immediate reductions, whereas others, such as stricter emission standards for NOx on new vessels only, will need longer before they have any effect (depending on how fast fleets are renewed).

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Truck versus ship emissions
Comparison of the environmental performance of different modes of transport is difficult, but by narrowing down the comparison to a few air pollutants, some conclusions can be made.

In terms of today's average vehicle and fuel, a ship will let out 30-50 times more sulphur per ton-kilometre than a truck (see Table 2 below). When diesel becomes even cleaner in 2005, the difference will increase to 150-300 times.

The highest permissible sulphur content of diesel oil for road traffic has been gradually brought down by legislation. As from 2000 it was lowered in the EU to 350 ppm (parts per million), and in 2005 it will be further reduced to 50 ppm. A further reduction to below 10 ppm is anticipated by 2009 - such fuels are already being placed on the market. In contrast, the average sulphur content of bunker fuels used in European waters is about 2.7-3 per cent, i.e. up to 30,000 ppm.

Turning to nitrogen oxides, ships now release about twice as much per ton-kilometre as the latest truck models, and the difference is set to increase (again see Table 2). In 2005, the emission standards for trucks in the EU will be cut from the present 5.0 g/kWh to 3.5, and in 2008 to 2.0 g/kWh.

Table 2. Emissions¹ from trucks on long hauls with different EU standards for emissions and from cargo vessels of various sizes. Figures in grams per ton-kilometre.

¹ Emissions are average in each case. Trucks: maximum overall weight 40 tons, loading 70 per cent, operating on diesel with a sulphur content of 300 ppm. Cargo vessel: bunker oil with and average sulphur content of 2.6 per cent, no cleaning of NOx. Source: www.ntm.a.se

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More information
More information on emissions from ships, including a 8-page briefing document with a full list of references, can be found on the Secretariat's website.

Information relating to the Commission's initiatives, including existing EU directives and several consultancy reports, is available at the website of the Environment Directorate of the European Commission www.europa.eu.int/comm/environment/air/transport.htm#3

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Published 21 May 2003.