Impact of Sea Shipping Emissions on Future Urban Air Quality in Major European Ports: A 2030 Scenario Analysis
Report no. 8/26: As land-based air pollutant emissions are projected to decline due to sectoral air quality and climate policies, sea shipping emissions under a “business-as-usual” scenario become increasingly important in explaining elevated concentrations of air pollutants. The intended decarbonisation of shipping though alternative fuels will further affect future air pollution from the sector. This study assesses how sea shipping, under a number of hypothetical sensitivity scenarios, would affect air pollutant emissions and air quality in Europe compared to other sectors, with a focus on four selected European seaport areas.
Sea shipping emissions were calculated using the Ship Traffic Emission Assessment Model (STEAM), combined with land-based emissions from the CAMS-REG inventory, and used as inputs to the LOTOS-EUROS chemistry transport model. The analysis domain covers mainland Europe and its surrounding sea corridors, with particular focus on Rotterdam (The Netherlands), Antwerp (Belgium), Marseille (France) and Piraeus in Athens (Greece).
A base case scenario for 2023 was defined (as the most recent year with complete and reliable data at the time of the study), with three sensitivity scenarios for 2030 developed for comparison. These are hypothetical scenarios and do not represent agreed upon or decided legislation. The “2030 BAU” scenario reflects the future situation under current and agreed policies until 2030, including emission control areas (ECA) in the Baltic Sea, North Sea, Mediterranean and Norwegian Sea. The “2030 LNG” scenario increases liquefied natural gas (LNG) energy share to 20% (compared to 11-12% in BAU 2030). The “2030 all-EU ECA” scenario assumes a hypothetical EU-wide sulphur and nitrogen emission control area (SECA and NECA) extending 200 nautical miles from the coastline, excluding the Canary Islands and the Azores. The extent and form of future ECAs remains uncertain and this scenario should be interpreted accordingly.
The air pollutants included in the assessment of the shipping and non-shipping emissions are oxides of nitrogen (NOx), sulphur oxides (SOx), particulate matter (PM10 and PM2.5), ammonia (NH3), carbon monoxide (CO), volatile organic compounds (VOC), and non-methane VOC (NMVOC). The air quality impact assessment focusses on the source apportionment results of PM (PM10 and PM2.5), nitrogen dioxide (NO2) and sulphur dioxide (SO2) that are the key pollutants in assessing current European air quality standards. This report presents primarily the assessment of NO2 (and PM), while other pollutants are presented in the accompanying Appendix.
The sensitivity scenarios assessed in this study reflect hypothetical stricter regulations, improved energy efficiency, and the adoption of alternative fuels. Shipping NOx emissions are projected to decrease by 13-19% by 2030 relative to 2023, representing a shipping share of 24-26% of total NOx emissions in 2030. NH3 emissions are projected to increase significantly due to the wider use of SCR and alternative fuels (such as LNG and methanol), however they remain a small contributor compared to land-based sources (<1%).
The hypothetical expansion of ECAs and uptake of alternative fuels will also alter the spatial emission distribution compared to 2023, with a SECA leading to reductions of 44-56% in SOx and 24-30% in PM2.5 emissions in the Mediterranean, relative to 2023. The shipping share of total SOx emissions in 2030 is estimated at 2-3%, while that of PM2.5 is 1%.
Land-based emissions are projected to decrease substantially by 2030 by 40% for NOx (2,048 kton), 25% for SOx (321 kton), and 35% for PM2.5 (462 kton), shifting the relative balance between sectors. For NOx, the sharper decline on land means that shipping’s share grows by 2-3% by 2030, while for SOx and PM2.5 the contribution of sea shipping falls by 2-3% and 1% respectively. At the port city scale, shipping dominates NOx emissions (approximately 70%) in the 2023 base case in Marseille and Athens (770 kton and 2,890 kton respectively), while it has a smaller but still significant role in Rotterdam and Antwerp of 25-30% (5,907 kton and 3,780 kton respectively).
The air quality modelling indicates that pollutant concentrations will reduce by 2030 across all scenarios relative to 2023: 22% (1.8 μg/m³) for NO2, 14% (1.3 μg/m³) for PM2.5 and 14% (0.4 μg/m³)
for SO2. Despite these reductions, shipping’s relative NO2 share across the European domain increases by approximately 5% compared to 2023, as land-based sectoral emissions reduce more. Differences between the 2030 scenarios are modest overall, but the LNG scenario generally lowers concentrations, while the all‑EU ECA scenario results in additional NO₂ and PM2.5 improvements along the Atlantic and the English Channel-Gibraltar corridors. NO₂ shipping concentrations are expected to decrease in the 2030 BAU scenario by 25% (3 μg/m3) over the North Sea and Baltic Sea, and by 18% (2 μg/m3) along the Mediterranean coasts compared to 2023. Along the EU waterways, the 2030 LNG scenario results in a larger reduction for NO2 with 23% (0.51 μg/m3), compared to 17% under the all-EU ECA scenario, whereas the latter is more efficient in reducing SO₂ concentrations with reductions of up 60% (0.11 μg/m3). For PM2.5, both scenarios result in a similar reduction of 32% (0.11 μg/m3).
In the four port-cities, reductions in NO2 concentrations are predicted across all 2030 scenarios. Traffic dominates in the Mediterranean cities (road traffic contributes approximately 60% (21 μg/m³) in Athens and 55% (7 μg/m³) in Marseille), while shipping is the largest NO₂ source in the BENELUX cities, contributing about 50% of urban NO₂ across all scenarios. Shipping’s relative share increases in all port-cities by 2030 despite decreasing absolute concentrations; e.g., shipping’s NO2 share rises by 8% in Athens and by 6% in Marseille. Shipping contributes 13% (Rotterdam), 10% (Antwerp), and 4% (Athens/Marseille) to PM2.5 in 2023, with its share decreasing slightly (by up to 1.5%) across all seaport cities in 2030 as industrial and stationary combustion sources become more prominent.
NO2 exceedances of the EU daily limit (50 µg/m³) in 2030 are only predicted in Athens (port and city) and in Rotterdam (port). When comparing against the non-binding WHO guideline (25 μg/m³), used here for indicative purposes, exceedances are predicted at all four port-cities, with shipping as the main contributor in Rotterdam and Antwerp, and road traffic as the main contributor in Athens and Marseille. For PM2.5 exceedances, road traffic and industry are the main contributors compared to shipping in all four port-cities.
Overall, while absolute sea shipping contributions decrease across all scenarios, shipping’s relative share grows in all four port-cities, as other sectors reduce faster. These findings highlight shipping as an important sector for future emission reduction strategies, and serve as a foundation for further refinement through improved emission inventories, higher spatial resolution, the inclusion of emerging pollutants, the integration of monitoring data and extended scenario horizons to 2050.