With new emission control regulations taking effect, gas as a ship fuel, once banned, is now re-emerging as an environmentally and economically attractive option. Compared to oil, natural gas has two key advantages: high efficiency and a lower environmental impact: 100% less of SOx, 85-90% less of NOx, and up to a 25% reduction in CO2 emissions.
Whilst there are a number of ways to meet emissions restrictions in Emission Control Areas, such as the use of low sulphur fuel or the installation of a scrubber, natural gas is an appealing answer. In liquid form natural gas cannot ignite: it is simply too cold. When evaporated into gaseous form it is still very difficult to find right mixture of gas and air to allow it to burn. Additionally, the ignition temperature of the air-gas mixture is very high (600°) and there are no surfaces in the engine room hot enough to ignite gas.
Until recently, LNG tankers were the only ships equipped with gas burning propulsion systems using their cargo boil off as fuel. These ships used to be equipped with boilers and steam turbines until the break through in 2004 of the construction of the first dual fuel diesel-electric propulsion on board the LNG tanker GAZ DE FRANCE ENERGY.
In early June 2009, the IMO Committee on Maritime Safety (MSC) lifted the ban on natural gas as a ship fuel by adopting Resolution MSC 285(86), called “Interim Guidelines on Safety for Natural Gas-Fuelled Engine Installations in Ships”. Developed by the IMO subcommittee on Bulk Liquid and Gases (BLG) with GL assistance over the past few years, the Interim Guidelines are the first step towards the envisioned general code for gas as a ship fuel, the so-called IGF Code, which is currently under development by IMO and is expected to enter into force conjointly with the revision of SOLAS 2014.
See also Platform supply vessel VIKING ENERGY.