Aarhus Universitets segl

No. 464: Reduction potentials for air pollution from national shipping in Denmark by retrofit of SCR and particulate filters

Jensen, S.S., Winther, M., Brandt, J., Frohn, L.M., 2021. Reduktionspotentialer for luftforurening fra national søfart i Danmark ved retrofit af SCR og partikelfiltre - Betydning for helbredseffekter og tilhørende eksterne omkostninger. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 43 s. - Videnskabelig rapport nr. 464. http://dce2.au.dk/pub/SR464.pdf


Background and purpose

This report is a deliverable under the Lighthouse Project, 'Maritime Emission Solutions in Coastal Waters' funded under the Danish Environmental Protection Agency's Development and Demonstration Programme (MUDP), and led by the Danish Technological Institute.

Aarhus University has carried out an impact assessment on health effects and related societal costs for a scenario based on a maximum scenario with the assumption that all ships under national sea traffic are retrofitted with the emission technology demonstrated in the project, where it is technically possible. The reduction technology includes particle filters and NOx catalysts also called SCR – Selective Catalytic Reduction. NOx denotes nitrogen oxides.

National sea traffic is subdivided into major ferry routes, smaller ferries such as island and short cut ferries, other national shipping, and freight transport between Denmark and Greenland/Faroe Islands.

The study

The starting point for assessing the potential for reduction of air pollution from ships in coastal waters by emission reduction solutions is based on the Danish National Emission Inventory for national sea traffic. The emissions are calculated based on activity data, emission factors and calculation methods, and emissions are geographically distributed in Danish waters with the so-called SPREAD model.

The reduction potential is based on the emission measurements carried out by the Danish Technological Institute on two vessels of the demonstrated reduction technology with particle filter and NOx catalyst (SCR). Its results have been generalised to the potential for reducing emissions from national sea traffic. The scenario for reducing emissions from national sea traffic is a maximum scenario, assuming that all ships that in principle could use the reduction technology would do so. In the emission reduction calculations, it is assumed that NOx emissions are reduced by 80% for ships using MDO (Marine Diesel Oil)/MGO (Marine Gas Oil) and HFO (Heavy Fuel Oil) in national sea traffic. For particulate emissions, it is assumed that it is possible to reduce by 99% with the particulate filter retrofitted in relation to the emissions from the engine without a filter for MDO/MGO diesel with a sulphur content of 50 ppm.

For heavy oil (HFO) with high sulphur content, it is not considered realistic to use particulate filters due to problems with ash and soot created by combustion and leading to clogging of the particulate filter. Particle emission consequences using filters and heavy oil are therefore not included in the subsequent emission reduction calculations, which applies to freight transport to Greenland/Faroe Islands. This means that the overall particle emission reduction will not be 99% but 52% when this is accounted for.

The emission reduction scenario is implemented in air quality calculations with DEHM (Danish Eulerian Hemispheric Model) in order to calculate the concentration difference between the base situation and the reduction scenario. The difference in concentrations is used in subsequent health calculations with the Economic Valuation of Air pollution (EVA) system.

Reductions in health effects and associated external costs resulting from the reduction scenario for national sea traffic are calculated with the EVA system. In economic terms, the costs associated with health effects of air pollution are referred to as indirect costs or externalities (external costs). It can also be described as the societal cost of air pollution.

Main conclusions

Total NOx and PM2.5 emissions from national sea traffic in 2018 are 11,939 tonnes and 277 tonnes, respectively. PM2.5 are particles below 2.5 micrometres in diameter.

Total NOx and PM2.5 emissions from national sea traffic represent 10% and 1.6% of total NOx and PM2.5 emissions, respectively, for all emission sources in the 2018 National Emissions Inventory.

The assumed percentage emission reductions correspond to total emission reductions of 9,541 tonnes of NOx and 144 tonnes of PM2.5 in 2018.

The health effects saved in terms of mortality and morbidity in the reduction scenario for national sea traffic are subdivided across ‘Europe’ (including Denmark) and ‘Denmark Only’.

In Denmark, the reduction scenario could potentially save 17 premature deaths per year, while the total number across Europe including Denmark is 98 premature deaths in 2018. 

The 17 premature deaths in Denmark that can be saved in the reduction scenario correspond to approx. 1.4% of the total number of premature deaths due to emissions from all Danish sources. The 98 premature deaths in Europe including Denmark similarly corresponds to approx. 3.2% of Denmark’s contribution to Europe including Denmark.

In addition, there will be a reduction in morbidity.

The total reduction in external costs of health effects from air pollution are DKK 332 million per year in the reduction scenario for national sea traffic, while it is DKK 1.7 billion per year for Europe including Denmark.

19% of the gains are in Denmark, while 81% of the gains are in the rest of Europe. The vast majority of gains is due to reduction in particles.

Every step from emissions to health effects and costs is associated with uncertainty. This is described in more details in the report. A German study estimates that overall uncertainty is probably approx. ±50% (Lelieveld et al., 2019). It is DCE's assessment that uncertainty of this magnitude is in line with the uncertainty to be expected in this type of study.