Sulphur and nitrogen oxide emissions
One of shipping’s main environmental impacts is emissions of sulphur and nitrogen oxides. In addition to health risks, the emissions also contribute to eutrophication and acidification of forests, soil and water.
Sulphur is naturally contained in all crude oils and is converted into sulphur dioxide on combustion. The amount of sulphur dioxide released during combustion of sulphur-containing fuel is proportional to the amount of sulphur in the fuel. The sulphur content of the fuel affects the emissions in several different ways. In addition to determining the amount of sulphur dioxide released, the sulphur content also affects emissions of particles and nitrogen oxides.
Maximum sulphur content may be regulated by different limit values. The requirements differ according to a vessel’s location. With effect from 1 January 2015, the sulphur content of fuel may not exceed 0.1% m/m in sulphur emission control areas (SECAs). These areas include the Baltic Sea, North Sea, English Channel, Canada and the United States. Outside sulphur emission control areas, the sulphur content of fuel may not exceed 3.5% m/m. By 2020, the limit will be reduced to 0.5% m/m.
To meet the requirements, a transition to low sulphur marine fuels or use of alternative fuels (e.g., LNG or methanol) will be necessary. In addition, the regulations are also an incentive to install scrubbers that clean exhaust gases.
Nitrogen oxides are formed during combustion. As a result of stricter legislation and companies’ own improvement efforts, there has been a significant reduction in emissions of nitrogen oxides from shipping in recent years.
The current emission limit values for nitrogen oxides are controlled by when the diesel engine was manufactured and when the vessel was built. All vessels in Concordia Maritime’s fleet were built after 1 January 2000 and therefore meet the IMO Tier 1 standards. This means that they have 13 percent lower nitrogen oxide emissions per tonne of fuel compared with ships that do not meet the standards. Two fleet vessels also meet the Tier 2 standards, and therefore have a further 15 percent lower nitrogen oxide emissions per tonne of fuel.