Exhaust gas treatment systems and hybrid propulsion systems

IMO developed strict rules regarding SOx, NOx and PM emissions. Regulations along Canada’s coast lines (including the Saint-Lawrence and Great Lakes) are even stricter as they are part of the North American Emission Control Area (ECA). To reduce emissions ships can either use low sulfur fuel (e.g. liquid natural gas) or use exhaust gas treatment technologies (scrubbers).

Exhaust gas treatment technologies or scrubbers

Scrubbers are meant to abate SOX emissions before they are released into the atmosphere. They allow the continuous use of bunker fuel, which is cheaper than refined fuels. However, not all types of vessels are built to fit a scrubber unless complex and expensive retrofits are undertaken.

Many different types of scrubbers exist and these various types are classified according to the technology they employ to clean the particles.

The two main categories of scrubbers are dry and wet systems. The wet scrubber systems are further divided into two sub-categories, depending on whether they are closed loop or open loop systems.

The open loop technology uses the alkaline properties of sea (salt) water to neutralize SOX emissions.

The closed loop technology uses the alkalizing power of fresh water and caustic soda to neutralize SOX emissions.
The closed loop system is more suitable for ships navigating in low alkalinity waters (low salinity), such as in the Great Lakes.

Both technologies require the treatment of the residual water before it can be discharged over board.
The use of scrubbers reduces SOx emissions by 90 % and PM emissions by 60-90%. (Source: Ce Delft mars 2015, Scrubbers – An economic and ecological assessment)
Today, a few ships operating in the St. Lawrence and Great Lakes are equipped with a scrubber in order to comply with regulations.

Hybrid propulsion systems

Hybrid diesel-electric or diesel-LNG propulsion systems use engines that are able to run on both diesel fuel and electrical power or liquid naturel gas (LNG). Hybrid systems allow the use of cleaner sources of energy (LNG or electric batteries), thus offering some operational flexibility.

In the St. Lawrence, the Société des Traversiers du Québec (STQ) was a pioneer in launching the first hybrid diesel-electric ferry in 2013, the NM Peter-Fraser, serving the small island of Île-Verte.
STQ also ordered the first LNG-driven ferry in North America, the F.A. Gauthier, in service since 2015 between Matane and the North Shore.

Another leader of this kind is Groupe Desgagnés, planning to build a series of four dual fuel tankers that are able to run on diesel, LNG and bunker fuel. The first tanker, the N/C Damia Desgagnés was successfully delivered in the spring of 2017. It is the first Canadian registered tanker and the world’s first asphalt tanker of its kind.

By using LNG, emissions are reduced by 85%, GHG by 25-30% and PM emissions are almost inexistent.