y and large, shipping is considered to be environmentally friendly because CO2 emissions are comparatively low. Even so, the industry is facing a major challenge. For cost reasons, most ships are powered by inexpensive heavy fuel oil with a sulfur content of up to 3.5 percent, which produces high sulfur dioxide emissions. This is set to change – for reasons including consideration for the environment and coastal populations.
The International Maritime Organization (IMO) is significantly tightening emission limits for ships. Since 2015, ships charting the waters of special Emission Control Areas, such as the North Sea and the Baltic Sea, are required to use fuels with a maximum 0.1 percent sulfur content or to deploy desulfurization technology. From 2020 on, all waters outside such areas will be subject to a sulfur content limit of 0.5 percent. This will affect some 50,000 commercial ships worldwide.
Drawing on decades of experience in flue-gas desulfurization, Bilfinger has successfully transferred this expertise to ocean shipping. Desulfurization systems, or scrubbers, reduce sulfur dioxide concentrations in emissions from vessels just as effectively as using low-sulfur fuels. When the flue gas is brought into contact with seawater, the sulfur dioxide is almost completely neutralized.
There are essentially three different types of processes: open-loop, closed-loop and hybrid. In the case of openloop scrubbers exhaust gases are cleaned in a continuous process and used wash water is discharged back into the sea in compliance with IMO specifications. A closed-loop process relies on absorbents added to the wash water to neutralize the gases. This processed water is stored in a tank for disposal on land. There is a clear trend toward hybrid scrubbers, which employ both open and closed systems. That is because a growing number of countries prohibit the discharge of polluted wash water off their coasts.
As a full-service provider, Bilfinger offers an all-inone service package – from development through production to maintenance. Bilfinger scrubbers stand out for their low operating costs and excellent environmental performance. Desulfurization systems pay for themselves after a period of 12 months to two and a half years.