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Abstract
RIVM developed a mobile lidar system to measure SO2 emissions of sea-going vessels. In three field campaigns, the SO2 emissions of a total of 110 ships on the Westerscheldt estuary were determined. As it turned out, a large number of those ships emitted huge quantities of SO2. Various measures have driven back emissions from other sources, such as traffic, industry and electricity generation. This causes the share of shipping in the total of the emissions to increase.
Sea-going ships are not allowed to use sulphur-rich fuel in territorial waters. This relatively cheap fuel may be on board, though, for use at sea. To what extend ship owners comply with this ban is not known. A breach is difficult to determine using traditional measurement methods because these require boarding the ship. This is a labour-intensive procedure, so only a few ships can be visited. The lidar measures from the shore and will determine the emission of nearly every passing ship. In addition, boarding the ship will alert the crew that a measurement is taking place, so they may adjust the type of fuel used. The lidar measures unnoticed.
On land, sulphur dioxide emissions of industrial installations are limited by licences. Dutch law puts demands on sources that emit more than 0.56 gram per second. All measured ships emitted more than that, the highest emission being 36 gram per second. This indicates the importance of recognising ocean shipping as a source of air pollution, both when issuing rules and when enforcing them.