Liquefied Natural Gas (LNG) seems to become an important fuel solution for sea-going vessels. The number of ships running on LNG is still limited but growing rapidly. Why does LNG bunkering make for a good alternative to conventional oil-based fuels?
The global gas reserves are huge, particularly in North America and Russia, but also in South America, the rest of Asia and Australia. It is estimated that the global gas reserves will last us at least another 200 years.
Let’s have a look at the LNG Value Chain:
As of January 2017, the global LNG shipping fleet counted 439 vessels, including FSRUs (Floating Storage Regasification Units) and floating storage units. In 2016, a total of 31 newbuilds, including two FSRUs, were delivered from shipyards, representing a 7% increase on 2015.
LNG as ship fuel for the future
LNG has great potential as ship fuel for three reasons:
- LNG consumption is clean, meeting the current and future emission standards
- Existing technology can be used: LNG carriers and coastal vessels and ferries in Europe already use duel fuel engines
- Price-wise, LNG is competitive with fuel oil
Most conventional ships will continue to use conventional oil-based fuel, as introducing LNG as fuel would result in having to install new systems and implement adapted risk management on board. However, LNG makes for a good alternative. After all, conventional fuels are running out and LNG is superbly placed to meet the ever stricter emissions requirements, as laid down in Marpol Annex VI.
This is explained by LNG’s composition of 87 – 99% Methane. Methane (CH4) is odourless, colourless, non-corrosive, non-flammable and non-toxic. Other chemical components of LNG are
- Ethane, ranging from less than 1% to 10%,
- Propane with a maximum of 5%,
- Butane of just over 1%
- Nitrogen with a maximum of 1%
- Minute traces of other hydrocarbons
Environmental protection legislation focuses on
- Sulphur oxides
- Nitrogen oxides
- Carbon dioxide
- Particulate member (linked to sulphur content)
The absence of sulphur and the limited amount of nitrogen means that burning LNG results in demonstrably lower emissions.
Burning methane also has numerous operational advantages:
- it requires no fuel heating, purifiers or hot filters
- burning methane leaves no sludge
- its ignition and combustion properties are excellent
- it reduces maintenance of pistons, cylinders, valves and turbochargers
it requires much less fuel system maintenance.
Risks and disadvantages of LNG
This post would not be objective if I didn’t mention the main risks and disadvantages, which include (but are not limited to):
- the extreme low temperatures (-162 degC), requiring special materials for storage as most materials become brittle and lose strength
- the need for more storage space of up to 150% of fuel oil storage space
- the dangers of leaks to staff, both due to the extreme cold and the risk of asphyxiation (the gas is odourless and colourless, making detection virtually impossible)
- strict separation of gas and air – burning methane can only be extinguished by removing either the oxygen or the methane
- as venting to air is not an option, a means to deal with boil off gas (BOG) is required
The main risk is ‘BLEVE’: boiling liquid/expanding vapour explosion. BLEVE is caused by a rupture in a storage facility, as the decreased internal pressure results in the liquid starting to evaporate rapidly and the valve capacity cannot handle to volume of gas. The risk is best managed through design, maintenance and procedures.
Last but not least, new build costs for LNG-fuelled vessels are much more expensive.
LNG bunkering
Suffice to say that LNG bunkering is not without risk either. Strict planning and monitoring, special demands on the equipment used and gearing methods to the installations of the receiving ship and the terminal tank, barge or truck make for specialist bunkering procedures, including vapour management.
Currently, the LNG bunkering infrastructure is still a problem as it is mainly concentrated in North-West Europe and the US Gulf and East coast. To become a success, the LNG-fuelled shipping industry and bunker infrastructure need to develop further and expand. Although bunkering initiatives are growing, for most ports LNG bunkering still poses too big an investment.
The way forward?
The pressure is on to make the shipping industry keep up with commitments made in line with the Paris agreement. The risks notwithstanding, LNG offers huge advantages, compared to fuel oil. Yet it is recognised that LNG is still a fossil fuel, producing CO2. Nevertheless, LNG is said to represent the most like alternative fuel for ships. The technology for ships’ engines and bunkering is available, and the environmental gains are clear, making LNG a viable fuel option.
Would you like to know more?
If you have any questions concerning the use of LNG as fuel, please do not hesitate to contact me. Alternatively, we offer in-house workshops and training, geared to your needs through our marine surveying academy.
The pressure is on to make the shipping industry keep up with commitments made in line with the Paris agreement.
