New tool calculates air pollution from shipping

Shipping emits considerable amounts of air pollutants which affect the climate, the natural environment and human health. In collaboration with the Swedish Maritime Administration (SMA), SMHI has developed a new system for calculating emissions from shipping. Knowledge of these has previously been very limited.

Shipping is undoubtedly the most significant source of sulphur emissions, as well as accounting for extensive emissions of nitrogen oxides, particles and Volatile Organic Compounds (VOCs). In climate-affecting emissions too, shipping is one of the main sources of emissions.

“Taken as a whole, emissions from shipping are a very important factor in air environment, as well as climate impact and acidification of our watercourses,” says David Segersson, Air Environment Consultant at SMHI. “At the same time though, there is great uncertainty regarding the scale of emissions in the shipping sector.”

Government agencies in co-operation

In collaboration with the Swedish Maritime Administration (SMA), SMHI has developed a new system for calculating the scale of emissions from shipping.

The SMA is responsible for the part of the system that contains details of the vessels and emission factors, which is the relationship between emissions and power. SMHI has developed the module that carries out the actual emission calculations, which is known as Shipair. The project is funded by the Swedish Environmental Protection Agency and the SMA.

Based on vessels’ positions

Shipair uses the GPS positions of ships sailing in the Baltic Sea and North Sea. The GPS positions are retrieved from the AIS (Automatic Identification System) which continuously sends vessel GPS positions via VHS radio. By law all large vessels must have an AIS transponder, although many smaller ships also use them.

High level of detail

The new system describes the vessels’ emissions in extremely high detail and the results can be presented as a grid or in the form of trajectories. Calculations may be made for any chosen area or time period. The figure below shows a grid display for nitrogen oxide (NOx) emissions in the Stockholm archipelago, with 25m spatial resolution.

Shipair emissioner
Emissions of nitrogen oxides (NOx) in Stockholm archipelago, April 2010. The scale gives total emission per grid square (25m x 25m).

Able to assess impact on health and environment

The system also enables spread projections, which can be used to determine the concentration of pollutants in the air. The results of these calculations can be used to assess the effect of shipping on health and the environment. Below is an example of air pollutant spread from a vessel off Concepción, Chile.

Shipair dispersionsbild
Projected spread of air pollutants from a vessel off Chile.

Shipair is currently only used by SMHI, but the aim is to make it available as a web application. Work on this will be completed over the next year. Potential users of the system include environmental authorities and ports.