Results from exploratory project on NOx emissions from Ocean Going Vessels (OGV) using remote sniffer measurements

Report, 2024

The NOx emissions from ships are governed by the International Maritime Organization (IMO) through MARPOL's Annex VI. This annex is part of the International Convention for the Prevention of Pollution from Ships. It establishes emission limits in the form of Tiers, which vary depending on the construction date of the ships and their engines. Our study concentrates on ships classified under Tiers 0 to II, as these are currently the most common vessels navigating the waters. In the study, mass- and brake-specific emissions of NOx at different ship engine loads were determined from six years of remote sniffer measurements at the Great Belt Bridge in Denmark. This bridge is situated over the main shipping channel connecting the Baltic Sea and the North Sea, with over 25,000 ships passing through annually. The analyzed data predominantly corresponds to 721 container ships, 425 RoRo vessels, 127 Reefers (refrigerated cargo), and 892 crude oil tankers, which are highly relevant for the ship types traversing Southern California waters to call Port of Los Angeles and the Port of Long Beach. Additionally, since vessels tend to reduce speed when approaching the Great Belt Bridge, the operational profiles of these ships are also very relevant for specific areas like Southern California, where multiple federal and local programs exist to encourage ships to voluntarily adopt reduced speeds as a strategy to either avoid whale strikes or decrease total emissions by reducing fuel consumption for the same distance travelled.