The International Maritime Organization (IMO) has set out a range of standards covering the reduction of nitrogen oxide (NOx) and sulphur oxide (SOx) emissions in maritime transportation. In April 2014 the IMO Marine Environment Protection Committee adopted stringent Tier III controls which require an 80% reduction of NOx emissions from Tier I (17.0 g/kWh) to be effective within emission control areas (ECA) from 2016.

The new approval verifies that Hitachi Zosen’s SCR system for marine engines is fully compliant with Tier III standards, making Hitachi Zosen the only marine diesel engine supplier to receive official approval from MAN. Tier III NOx standards are applicable to new ships constructed on or after January 1, 2016. Since it takes at least one year to design a new ship, the demand of new shipbuilding with SCR is rising significantly for NOx reduction systems.

The SCR system uses high-temperature exhaust gas upstream of the turbocharger to prevent excessive CO2 emissions and uses urea as a reductant to render NOx harmless for improved safety and user-friendliness.