SEICOR - Ship Emission Inspection with Calibration-free Optical Remote sensing

Ship emissions of particles, SO₂ and NO_x (the sum of NO and NO₂) are a significant contribution to air pollution, in particular in coastal areas and close to busy in-land shipping routes. Therefore, national and international regulations have been put in place to limit emissions and thereby minimize the impact of shipping on air quality. However, the monitoring of ship emissions is challenging, and so far, no automated systems are operational for systematic surveillance of compliance with regulations.

Active Optical Remote Sensing is one possible approach to measuring ship emissions. Briefly, a light source is set-up on one side of a river or port, and a reflector on the other side. The light path is positioned in such a way that the emission plume of passing ships is sampled. Using spectroscopic methods, the amounts of trace gases in the plume can be determined. With Automated Identification System (AIS) data, the plumes can be assigned to individual ships. The advantage of remote sensing over in-situ observations is a reduced dependence on wind direction, increasing the rate of successful measurements. A second important advantage is the self-calibration of the method, facilitating long-term autonomous operation without the need for on-site calibration.

This method has been successfully used in the UV/Vis wavelength range to detect SO₂ and NO₂ at the location of Wedel, a small town at the river Elbe, 10 km downriver of the port of Hamburg, Germany. Based on these data and a plume model, emission rates of NO_x and SO₂ in g s^-1 could be determined with an automated method (Krause et al., 2021).

While this type of measurement is useful in determining emission rates, often specific emissions relative to the amount of fuel burnt are of interest. This is particularly the case for SO₂, where regulations are based on limits for the fuel sulphur content. In order to extend the method to these quantities, an additional channel measuring CO₂ in the IR part of the spectrum has to be added to the instrument. The CO₂ can be used as a proxy of the amount of fuel burnt, and thereby also the energy used. In addition, direct NO measurements in the IR would reduce the uncertainties of the NO_x measurements.

The SEICOR project aims at developing such a system for automated long-term surveillance of emissions from ships and other, similar sources. It is based on the experience and tools from the measurements performed in Wedel. The new system will cover all parts of the measurements, from the instrument over data analysis of the emission factors to direct generation of warnings in case of high emissions. An automated reporting to the authorities, port operators and / or ship owners is planned. Here we present technical details and first results of the measurement and validation campaign which takes place in April 2025 in Wedel at the river Elbe.

The SEICOR project is funded by the Federal Ministry for economic affairs and climate action.