Reducing harmful emissions

In order to comply with ever-tightening regulations, shipping operators must find ways to reduce atmospheric emissions. Carrying as much as 90% of world trade, the international shipping industry is crucial to the intercontinental trade activities that underpin the global economy.

Stephen Harrison
Linde HiQ

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Article Summary

It has been estimated that if the growth of the past 150 years continues, the current 8 billion tonnes of cargo being transported across the globe annually will soar to 23 billion tonnes per year in the next 50 years. However, with the increasing volumes of cargo being transported annually, rising levels of marine emissions such as sulphur oxides (SOx), oxides of nitrogen (NOx), volatile organic compounds (VOCs), particulate matter (PM) and carbon dioxide (CO2) from the fuel used to power these vessels, are under close scrutiny by world environmental authorities.

The average size of merchant ships has steadily increased over the decades, as larger vessels reduce costs per load unit for crew, fuel, demurrage, insurance, servicing and ship maintenance. The speed at which these gigantic ships travel has also increased. Today the average speed of a merchant ship is about 15 knots or 28 km per hour, the equivalent of about 670 km a day, with newer ships capable of 25 to 30 knots (45 to 55 km per hour).

Ocean shipping can generally be divided into two cargo sub-markets – bulk or crude / refined petroleum products and dry cargo. Bulk goods comprise iron ore, coal, grain, phosphates and bauxite, as well as non-ferrous metal ores, feed and fertilizers. However, crude oil is the big player worldwide, accounting for about 25% of all goods transported by sea.

While the global shipping industry is responsible for only 3% of greenhouse gases, this contribution has recently prompted significant changes in the legislated control of emissions from this sector. A key concern is the health of communities living in close proximity to major ports and shipping lanes.

One of the busiest maritime routes revolves around the area entering in, and departing out of, Hamburg in Northern Germany. Almost 
80000 ships call into Hamburg and other European ports each year, adding significantly to air pollution due to high sulphur and the heavy bunker fuels burnt at sea and also at dockside. Hamburg is Europe’s largest container port after Rotterdam and citizens there are in support of urgent action to reduce the sulphur emissions limit.

Another prime example is that of the 30 km Bosphorus Strait in Turkey, one of the most highly trafficked shipping channels in the world. Only 3.6 km wide at its broadest section and less than 1 km at its narrowest, the Bosphorus flows directly through the city of Istanbul, which has a population of some 15 million people. On average, 140 international trade vessels, including oil tankers, pass through the straits every day.

Owing to strong currents in this channel, ships must use their engines on high power which can lead to a significant issue regarding shipping emissions and its environmental impact on the city. Maritime traffic on the Bosphorous is increasing and exhaust emissions (SOx, NOx, CO2, VOCs and PM) from international shipping, as well as vehicle and passenger transit vessels which cross the Straits daily and account for up to three hundred ferries a day - are posing a health and general environmental hazard to the city’s inhabitants. This potential human health issue has led to the Turkish government investigating the opening of a new open water channel to advance Mediterranean trade before the problem increases in severity. And clearly, emissions control is another possible mitigation.

For environmental reasons Liquefied Natural Gas (LNG) and even wind propulsion and nuclear power are occasionally employed to propel commercial shipping, but the majority still use a reciprocating diesel engine as their prime mover, powered by fuel oil, also known as bunker oil. Combustion of bunker oil in ships generates the same pollution components as those emitted from road transport vehicles and is similar to the emissions footprint from other fossil fuel burning industries such as electrical power plants. However, most of the sulphur emissions from land based transport are eliminated by the use of low sulphur fuels, where the sulphur is removed at the refinery. And, there is also a growing trend for automotive sector NOx emissions to be reduced using selective catalytic reduction (SCR) with the addition of Urea as a source of Ammonia. In the power generation industry, SO2, NOx and PM pollutant emissions are reduced through the use of wet gas scrubbing for SO2 removal, by reaction of SO2 with lime, reaction of NOx with ammonia in SCR and selective non-catalytic reduction (SNCR) technologies and electrostatic precipitation for PM reduction. These techniques are highly effective in cleaning the flue gas from the power plants. By comparison, the control of these emissions from shipping has historically been less rigorous, but the trend is going in a similar direction and is being driven by phased implementation of environmental protection legislation through the International Maritime Organization (IMO) and MARPOL.

Shipping takes its turn in the legislative queue
Marine pollution is regulated internationally and one of the key international conventions for the prevention of pollution at sea is MARPOL 73/78, adopted by the IMO in 1973, and later updated in 1978 after several severe tanker accidents. The convention includes regulations aimed at preventing and reducing pollution at sea from ships, including both accidental pollution and pollution from routine operations. Today, countries who have signed up to the MARPOL legislation represent 98% of international shipping.

This convention has seen the designation of special so-called Emission Control Areas (ECAs) where stricter controls on the principal marine emissions NOx and SO2 have been put in place. These ECAs are generally designated in densely populated areas close to high levels of shipping and their regulations are also cascaded into regional and local legislation through regional authorities such as the European Union.

Following agreement at the IMO and incorporation into European law, the Baltic Sea became the first fully implemented ECA in August 2006, followed a year later by the designation of the North Sea and English Channel as the second ECA. In August 2012, new ECAs were designated for ships trading off the coasts of Canada, the USA and the French overseas collectivity of Saint-Pierre and Miquelon. A new area, the United States Caribbean Sea ECA, covering certain waters adjacent to the coasts of Puerto Rico and the United States Virgin Islands, took effect from January 2014. Further ECAs seem likely to be proposed for Norway and Japan, and possibly for the Mediterranean and Black Seas and the seas around Mexico, Korea and, potentially also the heavily used Malacca Strait.

The issue of designating the Malacca Strait as an ECA is the subject of frequent debate, since the diversity and scale of shipping activities in this area is massive and it would be extremely challenging to monitor and enforce the emission regulations. Effectively, this inclusion would mean regulating most of the world’s shipping operators. Whilst this might be highly desirable from an environmental perspective, it would also be highly complex.

A phased reduction of SOx emissions in ECAs saw the allowable amount of fuel sulphur reduced to from 1.5% to 1.0% in July 2010 and this has been further lowered to 0.1% in January 2015. Outside of ECAs, the current global limit of 3.5% sulphur-in-fuel was reduced from 4.5% to 3.5% in January 2012, and is likely to be further reduced to 0.5% in 2020.

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