As we prepare to adapt our fleet in response to MARPOL legislation, there's been much talk about scrubbers, and how we're fitting these to six of our ships. But what actually is a scrubber?
A brief guide to a scrubber and what it will do for our ships:
A scrubber is a large piece of equipment fitted in the exhaust system of a ship, almost like a large version of a catalytic convertor fitted to a car exhaust.
Once a scrubber is installed it cleans the ship's exhaust, removing about 90% of the sulphur dioxide, this enables us to comply with the new MARPOL VI limit of 0.1% sulphur emissions. They have the added benefit of removing about 70% of particulate matter which is also harmful to health.
How it works.
Although a scrubber is not, strictly speaking, a filter it does perform a similar function by using sea water to wash sulphur dioxide from exhaust gases.
Exhaust gas enters the scrubber and is sprayed with seawater in three different stages. The sulphur oxide in the exhaust reacts with water and forms sulphuric acid. Chemicals are not required since the natural alkalinity of seawater neutralises the acid.
One scrubber is required for each engine, so when we say that we're fitting scrubbers to six of our ships; we're actually investing in a much larger number of scrubbers. For example, Normandie, Mont St Michel and Pont-Aven each have seven engines (four for propulsion, and three for electrical power) - so each will require seven scrubbers. This perhaps goes some way to explaining the high cost of installing scrubbers - approximately £10 million per ship - as well as the length of time it takes - around eight weeks.
However, these changes will make our ships greener than ever and we will result in us having a very environmentally friendly ferry fleet