Calculating emissions from shipping

Shipping is a significant source of atmospheric pollutants, which contribute to climate change and have negative effects on human health and the environment.

A new study has applied detailed methods to estimate global fuel consumption from international shipping, including for the first time, an estimation of emissions from the global fleet while in port. Developing appropriate policies to monitor and regulate global maritime traffic requires an accurate emissions inventory.

Norwegian researchers used improved modelling techniques and input data to estimate fuel-based emissions for the international maritime fleet during 2004. They calculated the time spent at sea and in port for seven sizes of ships and 15 ship types to estimate activity levels of commercial shipping across all geographic regions of the world. Global emissions inventories were also calculated for a range of pollutants: CO2, NO2, SO2, CO, CH4, VOC (Volatile Organic Compounds), N2O, BC (Black Carbon) and OC (Organic Carbon).

Total fuel consumption during 2004 was found to be approximately 217 million tonnes (Mt), with bulk carriers, container vessels and oil tankers accounting for nearly 50 per cent of this figure. About 11 Mt, or five per cent of total consumption, was used in port for operations such as loading and unloading. Bulk carriers, container vessels and oil tankers also accounted for about half of the total air emissions of the world's fleet, with most of these emissions (95 per cent) occurring when the vessels were at sea.

Overall, container ships had the largest total emissions of all ship types, particularly in the Pacific and along major trade routes between Asia and North America. Further increases are expected from the growing share of container traffic in the shipping trade. Bulk carriers, container vessels and oil tankers also accounted for about half of the total air emissions of the world's fleet, with most of these emissions (95 per cent) occurring when the vessels were at sea. Overall, container ships had the largest total emissions of all ship types, particularly in the Pacific and along major trade routes between Asia and North America. Further increases are expected from the growing share of container traffic in the shipping trade.

Emissions can be transported hundreds of kilometres through the air, affecting areas of land at great distances from the source of pollution. For example, shipping was estimated to have contributed to around 5-15 per cent of surface ozone over western Europe and 15-25 per cent of surface ozone over western North America. Between 2004 and 2007, greater global trade would have increased fuel consumption by a further 19 per cent, to an estimated 258 Mt during 2007. In particular, trade with Asia, especially container traffic, has significantly increased since 2004. Source: Dalsøren, S.B., Eide, M.S., Endresen, Ø., et al. (2008). Update on emissions and environmental impacts from the international fleet of ships. The contribution from major ship types and ports.

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