New Study Reveals High NOx Emissions from Ships

A recent working paper by the International Council on Clean Transportation has shed light on the alarming levels of nitrogen oxide (NOx) emissions from ships.

The study analyzed 615 samples of real-world emissions from 545 ships operating in Danish waters in 2019, using sniffers attached to helicopters to gather data.

Surprisingly, the findings indicate that newer Tier II engines actually had higher NOx emission rates than older Tier I engines. The study also revealed that there was no significant difference in emissions between unregulated Tier 0 engines and Tier II engines.

Of particular concern is the fact that the highest mean NOx emission rates were observed at main engine loads below 25%, with an average of 12 grams per kilowatt-hour (g/kWh) across all vessel types and engine tiers. As engine loads increased, emission rates decreased, with mean rates dropping to 8.1 g/kWh at loads exceeding 75%. This finding contradicts existing assumptions in NOx test cycles for marine engines, revealing that marine engines typically operate at lower engine loads, rather than higher engine loads as previously believed.

The study suggests that current NOx regulations may need revision to effectively reduce air pollution. Its authors urge the International Maritime Organization to consider implementing not-to-exceed (NTE) standards for both new and existing ships, focusing on operations at low loads. Additionally, the study highlights the importance of including a test point below 25% load in future regulations.

These findings emphasize the need for stronger measures to tackle ship emissions and protect air quality in coastal areas. Addressing the issue of NOx pollution from ships is crucial in the ongoing efforts to combat climate change and promote sustainable maritime practices.

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