Environmental and price challenges are driving the interest in alternative ship fuels, but the number of realistic candidates is small, finds the latest study Alternative Fuels and Technologies for Greener Shipping of classification society DNV GL.

The study believed liquefied natural gas (LNG), liquefied petroleum gas (LPG), methanol, biofuel and hydrogen to be the most promising candidates to be used by the shipping industry as an alternative marine fuel.

“Among them, LNG has already overcome the hurdles related to international legislation, and methanol and biofuels will follow suit very soon. It will be a while before LPG and hydrogen are covered by appropriate new regulations within the IMO IGF Code, as well,” it finds.

“The existing and upcoming environmental restrictions can be met by all alternative fuels using existing technology. Fuel cells can use all available alternative fuels and achieve efficiencies comparable to, or better than, those of current propulsion systems.”

However, the study notes fuel-cell technology for ships to be still in its “infancy”. The most advanced developments to date have been achieved by the projects running under the umbrella of the e4ships lighthouse project in Germany, with Meyer Werft and ThyssenKrupp Marine Systems heading the projects for seagoing ships.

Wind-assisted propulsion, meanwhile, could potentially reduce fuel consumption, especially when used for slow ships, but the business case remains difficult.

Batteries as a means to store energy can be considered as an alternative fuel source in the widest sense. Still, they have major potential for ships running on short distances and can be used to boost the efficiency of the propulsion system in any ship, but are unable to substitute fuel in deep-sea shipping.

With low-sulphur and alternative fuels becoming more widely available, the well-known combined cycle gas and steam turbine technology represents a viable alternative for highpower ship propulsion systems.

“All fuel alternatives discussed here could meet the foreseeable volume requirements for shipping over the coming years,” it notes.

“A major increase in consumption would require an appropriate increase in production capacity; the only exception is LNG, which is available in sufficient quantities today to meet the potential requirement of the shipping industry for many years.

“Without taxation or subsidies, renewable fuels will find it difficult to compete with the prices of conventional fossil fuels. “

In short, the study finds LNG and LPG to be the only fossil fuels capable of achieving a reasonable CO2 emissions reduction.

CO2-neutral shipping seems possible only with fuels produced from regenerative sources.

If the shipping sector resorts to synthetic fuels produced from hydrogen and CO2 using regenerative energy, the available alternatives will be liquefied methane (which is very similar to LNG) and diesel-like fuels.

Photo credit: DNV GL
Published: 11 May, 2018