Liquid Natural Gas (LNG) is in focus for new consumers due to the environmental benefit and the increasing availability as an alternative to oil. It is composed of 90% methane which is a colourless gas with a boiling point of –162º Celsius. So it is quite different from HFO and diesel.
It can, however, be used for marine service provided it is kept under pressure and in insulated cylindrical tanks. Short sea shipping has been an early starter in spite of lack of established infrastructure comparable to what we are used to for oil.
This article talks about the experience in Norway with gas-driven ferries and other small ships in short sea trade. One important driver is the environmental benefits, especially in congested areas with heavy traffic and dense population. It concludes that large ships engaged in deep sea shipping are therefore normally not candidates for LNG fuel for propulsion.
But could LNG be a viable alternative for big container ships in port and ECA/SECA areas? Big cities close to container ports like LA/LB could face a better future if LNG could provide perfectly clean reefer power by using LNG. Could be an alternative to cold ironing or distillate fuels?
Small scale LNG, an overview
The use of LNG as fuel for propulsion onboard merchant ships has been commonly practiced for LNG carriers only. Practically all LNG carriers delivered until just a few years ago use the boil-off from their cargo as fuel for steam boilers and propulsion.
Now, however, a new development is under way. A wider range of applications for LNG is evolving. New shore-based consumers, and use of LNG as fuel for engines onboard ships other than LNG carriers, are important factors in this development.
LNG is being independently supplied to other categories and smaller consumers. This requires establishment of new infrastructure for distribution of LNG in smaller quantities. The evolution of a new Small Scale LNG is progressing and is expected to gain momentum in the years to come, especially as regulators impose caps on greenhouse gas emissions.
Today there are 13 small (below 13,000 GWT) LNG carriers in operation worldwide, distributing LNG on a small scale. The first one was delivered in 1993 in Japan. Only four such vessels were delivered before the year 2000, all to Far East owners. As of the end of March 2009, the global order book has six small (2 x 10,000 m3 + 4 x12,000 m3) LNG carriers on order, all being built in China and owned by Norwegian comany I.M. Skaugen. These vessels are also intended for ethylene, LPG and VCM cargos in addition to LNG.
New shore-based consumers of energy from LNG, previously consuming energy from other sources, are important for this development. Making steady progress in Norway, thet may be indicative of coming developments in other parts of the world.
Drivers Behind Small Scale LNG Development
There are a number of general drivers behind the development of small scale LNG. Some of them are overlapping and related. Among the most important ones are:
• economical considerations of fuel prices today and projected developments
• increasing availability of LNG
• environmental benefits
• regulatory developments
• technical developments/improvements, facilitating the use of LNG and making it more attractive
• operational benefits
• charterers’ preference
• profiling/brand management
One limiting factor LNG has lower energy density than fuel oil. The fuel oil volume has to be doubled to achieve the equivalent energy content for LNG.
For practical reasons and in order not to sacrifice cargo capacity, the operational range due to bunker capacity of the vessel, will normally be reduced. LNG is therefore a fuel alternative primarily for vessels which can re-fuel relatively often. This fuel alternative is therefore most applicable to short sea shipping. Large vessels engaged in deep sea shipping are therefore normally not candidates for LNG fuel for propulsion, at least not with present technologies.
The Environmental Aspect of LNG
LNG is often highlighted as the cleanest fossil fuel alternative. When compared to diesel oil used for piston engines, LNG has the following potential benefits/ reduced emissions as opposed to conventional diesel engines. (Illustration: Rolls-Royce).
It is important to note that the gas engines available today can be divided in two main categories:
• dual fuel engines (e.g. Wärtsilä, Man)
• lean-burn gas engine (e.g. Rolls-Royce, Mitsubishi)
The different engines and engine/ propulsion arrangements have varying characteristics and levels of efficiency.
The true reduction of greenhouse gas emissions in each individual case will of course depend on the total efficiency of the chosen alternative. It should be noted here, however, that methane slip, i.e. in-complete combustion of methane (CH4) in the cylinders, releasing methane on the exhaust side, will negatively influence the reduction of greenhouse gases significantly, and in worst cases eliminate the gains from CO2 reductions.
In consideration of the fact that CH4 is more than 20 times more powerful than CO2 as a greenhouse gas, release of even small volumes of methane easily spoils the potential gains.
The different engines are different in this respect, but the tendency to release methane tends to be highest when engines are operating at lower loads. Engine manufacturers are of course aware of this challenge, and research is being carried out to minimise the methane slip. Prospects for important improvements are claimed to be very good.
Achieving maximum reduction of greenhouse gases from gas-fuelled vessels will require careful selection of engines and arrangements fit for the application and modes of operation (e.g. full load or frequent part load) in each case.
The EU and the IMO are aiming for very ambitious CO2 reductions in the years to come. Even if shipping is the most energy efficient mode of transportation, we must be prepared to be challenged based on shipping’s own reduction potential. In this setting, LNG-fuelled vessels will certainly be one significant part of the solution.
Small Scale LNG in Norway
Small scale LNG has not been developed many places in the world as of yet, but we see a rapidly increasing interest. There have been small scale LNG activities in Japan and South East Asia, and progress has been very good in Norway.
One reason for the development in Norway is the quite complete range of players in the Norwegian small scale LNG cluster, representing all of the different elements necessary to promote and amplify the trend. These include:
• LNG producers
• LNG distributors
• Owner of (world’s smallest) LNG carrier, for local LNG distribution
• Various land-based industries and consumers buying LNG
• Owners prepared to invest and test out new and future-oriented concepts
• Ship designers who understand the challenges involved
• Yards prepared to offer and build new concepts
• Charterers prepared to sign contracts involving new technology
• Road authorities specifying LNG fuel for new ferries
• Engine makers which offer gas-fueled alternatives
• Designers/builders of LNG bunker tanks and gas fuel systems
• Flag authorities prepared to accept the new developments
• Class societies which is developing standards for LNG-fired engines along with associated safety aspects
• Politicians and authorities implementing NOx emission tax for vessels operating between Norwegian ports, and associated NOx fund to subsidise measures to reduce NOx (among them use of LNG as fuel)
• Research institutions (e.g. Marintek in Trondheim)
• Available funding for development and improvement of LNG-based marine transportation alternatives.
We should note that the international shipping community also has a number of highly qualified specialists and suppliers of equipment relevant for small scale LNG. It is therefore important to emphasise that many non-Norwegian suppliers have also been involved in the development of small scale LNG in Norway, for instance yards, designers, builders of gas engines and fuel tanks, and the like.
The importance of the list above is be-lieved to be that attitudes and motivation to develop something new in Norway have been positively influenced by a very complete maritime cluster and the creative and constructive interaction between the players involved.
Conclusions
Shipping is the most energy-efficient mode of transportation. More goods should be removed from the roads and onboard ships, particularly in densely populated areas, to reduce traffic congestion. LNG-fuelled ship transportation would further minimise greenhouse gas emissions.
Small scale LNG has a great potential for development in the years to come, and will have to be part of the solution to reach ambitious emission targets set by national, regional and international authorities and bodies.
For practical reasons LNG as marine fuel is most convenient for short sea shipping, and in the near term for vessels trading between fixed ports or in areas where LNG fuel is conveniently available.
Infrastructure for distribution of LNG has to be developed further. Authorities can do more to promote development of small scale LNG by establishing incentives and contributing to practical solutions.
It is essential that “methane slip” is further reduced in order to achieve the full potential environmental benefits of LNG as a fuel. Engine manufacturers are working on this challenge; the potential for improvement is said to be high.
Small scale LNG has progressed quite far in Norway, which has a complete cluster of relevant participants. There are lessons to be learned from the “Norwegian small scale LNG experience”.
The technology, concepts and safety standards are established, but will be further developed as practical experience with the technologies and operations is gained.
For small scale LNG shipping the risk picture is similar to other conventional maritime solutions.
Some owners are enthusiasts and pioneers, contributing to the development at their own expense, assuming future rewards.
Continuing competence development, safety consciousness, and relevant procedures are essential for the future success of small scale LNG.
Date: 2009-12-17