Pioneering for the environment

In 2010, Sirius Shipping’s chemical tanker Olympus became the first in the world to reduce its NOx emissions by 90 per cent by retrofitting. Today, Olympus sails with pioneering equipment that controls emissions on all engines, main and auxiliary, and saves fuel by recycling exhaust heat.


It is an inescapable fact that the environmental impact of maritime shipping must be greatly reduced. Being aware of threats to the global environment like acid rain, eutrophication and climate change, forms a natural part of daily operations at Sirius Shipping. The company’s efforts to achieve green shipping are conducted in several ways:

“We look at LNG propulsion, ballast and waste water treatment, onboard energy recycling, cold ironing, biodegradable lubricants and many other measures”, says Jonas Backman, Managing Director of Sirius Shipping. “We transport oil and chemicals in a sensitive environment. Our vision is for our ships to emit no harmful substances at all.”

A major step was taken in that direction when a combination of selective catalytic reduction (SCR) and economiser technology was installed on board Sirius Shipping’s chemical tanker Olympus. The installation means the ship’s NOx emissions are reduced by 90 per cent or about 200 tonnes per year. In addition, fuel consumption was reduced by approximately 100 tonnes per year. The total annual CO2 emission reduction is around 300 tonnes. Together, the installation of the Catamiser and the SCR unit has made Olympus the world’s cleanest tanker with conventional diesel propulsion.

We transport oil and chemicals in a sensitive environment. Our vision is for our ships to emit no harmful substances at all.

Jonas Backman, Managing Director of Sirius Shipping.

How it works

The Catamiser combines an SCR catalyst, which removes NOx from exhaust gases, and an economiser, which recovers and recycles heat from exhaust gases, fitted together into a single unit. Thus the unit not only reduces NOx and CO2 emissions by removing NOx from the exhaust, but also by reducing fuel consumption through recycling exhaust heat. In this way, further NOx and CO2 emission reductions are achieved.

On the Olympus, the exhaust from all three Volvo Penta D34AMS auxiliary engines passes through the Catamiser’s SCR reactor, where the catalytic process removes most of the NOx. The exhaust gasses then pass through the Catamiser’s exhaust gas boiler, where the heat is recovered and distributed through heat exchangers to the ship’s heating systems. The exhaust from the main engine, an MAK 9M32C, are led through a separate SCR unit. The heat from the main engine’s exhaust is also recovered in a separate gas boiler. The exhausts from all engines are jointly led through a silencer before release to atmosphere.

Limited space is always a difficulty encountered when retrofitting emission control equipment to ships, as all the units are located in the funnel.

“Space is always a huge challenge. Installing a Catamiser instead of separate catalyser and economizer units saves a great deal of space,” says Anders Bejre, Technical Superintendent at Sirius Shipping and Project Manager for the Catamiser project.

Another very positive effect of the Catamiser installation was noise reduction:

“The Catamiser itself has a great dampening effect, especially on high-frequency noise. When we tested the noise levels on one auxiliary engine at the shipyard after the installation, the difference was incredible”, says Anders Bejre.