Recent ships emit more nitrogen in the North Sea

Our country has long been known as a pioneer in the international fight against air pollution at sea. And since 2020, the sniffer sensor of the Belgian air surveillance aircraft is the only one in the world to also have a NOx sensor on board. In 2020 and 2021, 1,407 ships were monitored in this way. That monitoring showed that the average nitrogen value of ships built between 2011 and 2020, the so-called Tier II ships, was higher than older ships, Tier I and Tier 0. Just like the Euro standard for cars, the international maritime NOx emission limits defined based on the year of construction: for more recent ships, the emission standards are stricter.

To protect the densely populated countries around the North Sea against the harmful impact of NOx, the Belgian part of the North Sea, among others, is part of a low-emission zone for NOx. The RBINS points out that the reduction of NOx emissions from shipping in the North Sea is particularly relevant because of the very high shipping density and busy shipping routes close to land.

The majority of the ships meet the emission standards, but it is surprising that the NOx emissions of recent ships are higher on average. “This is remarkable since international regulations aim to gradually reduce NOx emissions in the low-emission zone,” it said in a press release on Wednesday.

Further research

Average NOx emissions for Tier I ships were 12.6 g NOx/kWh, while for Tier II ships it was 13.5 g NOx/kWh. There were also more Tier II ships with NOx emission values ​​above a predetermined threshold value.

Further research will be needed into the possible causes, but the way the regulations for Tier II ships are set up already plays a role. The NOx emissions at lower engine powers have less weight in the set standards. And it is simply the case that ships, due to the busy traffic in the Belgian part of the North Sea, often sail with a lower engine power. At lower power levels, NOx emissions are slightly higher. “The international regulations that aim to reduce nitrogen emissions are therefore not adapted to the specific sailing conditions in the southern North Sea,” said the RBINS.

The negative effects of NOx are well known: they penetrate deep into the lungs and are a contributing factor to respiratory and cardiovascular diseases. They also play an important role in the formation of ozone and contribute to the formation of particulate matter.