Liquefied Natural Gas (LNG) has recently become a popular fuel in the
shipping industry due to its low emissions and high energy density. However, it
requires one or more bulky cryogenic tanks for storage onboard. Considering a
traditional fast ferry, it is hard to find onboard a location for tanks, thus hindering
the retrofit of existing ships. In this context, Compressed Natural Gas (CNG) might
be a viable solution, since it can be more flexibly stored onboard and has greater
availability in minor ports compared to LNG. Hence, this article investigates the
feasibility ofretrofitting the propulsion system of a fast ferry to employ CNG as fuel.
After a review of the pros and cons of CNG and LNG as alternative fuels to marine
diesel oil (MDO), a critical analysis of the technical requirements for retrofitting a
fast ferry with CNG propulsion systems is carried out. Defined the layout and
changes of the refitted unit, its performances are assessed on atest operative scenario.
The study concludes that CNG retrofitting is technically feasible and provides
several benefits, including lower emissions, higher levels of performance and higher
reliability compared to LNG. Nevertheless, the retrofit requires significant changes
to the ship layout and its fuel system to fit the required number of CNG cylinders.
