Remote Measurements of Ship Emissions
The combustion of sulphur-containing fossil fuels gives rise to emissions of sulphur
dioxide. Nitrogen oxides are also emitted when fuels are burned. The International
Maritime Organization (IMO) has ratified regulations regarding Sulphur Fuel Content
(SFC) and NOx emissions from the shipping sector. There is economic incentive to ignore
legislation and run with cheaper residual fuel that contains high concentrations of sulphur.
In open waters, there is no effective method of controlling whether ships are running on
low or high sulphur fuel.
A surveillance system, denoted Identification of Gross Polluting Ships (IGPS), has been
developed and used with the objective of enforcing the use of low sulphur fuel and NOx
abatement equipment according to the new conventions within the IMO.
The system is foremost an airborne system consisting of an optical remote measuring
system for total emission measurements of SO2 or NO2 from ships. When the emission
values reach a certain threshold, an aircraft flies into the ship’s exhaust and takes in situ
measurements, denoted the sniffer system, from which SFC and NOx g/kg fuel
measurements are obtained.
The uncertainty for the optical measurements is estimated to be approximately 45% with
optical and wind as the largest uncertainty sources. Estimates of the overall uncertainty
for the sniffer measurements, derived during a campaign in Rotterdam, corresponds to
14% for SO2 (S%) and 33% for NO (g/kg fuel). For the emission factors of NOx versus
axial power, g/kWh, the uncertainty is 37%. It should be noted that the NO uncertainty
was unusually high due to instrument problems.
Measurement campaigns have been carried out in the Baltic and North Seas using a
CASA-212 aeroplane and a Dauphin helicopter. Optical measurements show the
possibility to detect SO2 and NO2 emission from ships. Many of the ocean going ships
had a total emission of 60 kg/h SO2. The sniffer measurements showed good agreement
with the current IMO regulations for the majority of ships. When the strictest IMO
regulation of 0.1% SFC is introduced, ships using fuels with 0.5-4.5% SFC will be easily
detected with the current uncertainties.
in situ measurements