Zero Emission Vessels – roadmap to 2050

At MEPC 72 in April 2018, the IMO dropped something of a bombshell on shipping with its announcement of an ambitious roadmap to reduce the industry’s greenhouse gas emissions in a stepped approach.

by Gillian Lovering

The IMO’s strategy envisages for the first time a reduction in total GHG emissions and by at least 50% by 2050 compared to 2008, while, at the same time, pursuing efforts towards phasing them out entirely. In addition, the strategy looks for energy efficiency improvement by 40% in 2030 and 70% in 2050 – also compared to 2008.

Although there seems to be a view that this is all about CO2 reduction, this is not actually the case. Certainly, the energy efficiency improvements are all about CO2 because they fall under EEDI and soon perhaps the EEXI rules. But the 50% by 2050 covers Greenhouse Gases and in addition to CO2 this will include several other gases.

Having said that, the prime source of emissions on vessels do come from burning fuels and aside from a small number of fully electric ferries powered by batteries charged from the shore grid, virtually every vessel afloat uses some type of fossil fuel. Some could quite easily switch to battery power fully or partially, bunker barges, water barges, some tugs and crew transfer vessels are examples, but for vessels that operate for long periods away from shore, battery power is not a viable option.

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Putting aside the question of fuels for the moment there are three alternatives to the internal combustion engine that could be used to move ships. Wind power, fuel cells and nuclear power.

Wind power has the longest heritage of any in shipping but there are many reasons why it was dropped in favour of steam and motor ships. While there are many projects aiming to bring back sails and to use other forms of wind assistance such as Flettner rotors or variations of them and kites, most analysts agree that wind power alone has no future in modern shipping.

However, it has a very strong claim in the area of assisting in increasing efficiency and will doubtless be exploited in many ways to improve EEDI and EEXI ratings.

Fuel cells have been touted as the future for shipping for more than a decade but there have been only a handful of instances of their use on ships and then only as a minor contributor. There are several types of fuel cells that might be used but unless pure hydrogen is carried on board, then there will be emissions produced.

Although the stack (where hydrogen is combined with oxygen to produce heat and electricity) itself is emission free, the reformer unit where hydrogen is released from methanol, methane, fuel oil or what ever other hydrogen carrier is being used will produce CO2, CO and various other emissions. In addition, the processes that take place in a fuel cell require high operating temperatures which requires an energy source of its own.

Despite its stuttering start, fuel cell technology looks certain to enter the marine field in the near future. Wärtsilä and offshore operator Eidesvik have announced that a 2MW system could be in use by 2023 and numerous other developers have projects with a similar time scale.

Hydrogen can also be burned in an internal combustion engine and there are already some cases where this is done in road vehicles and in a handful of marine uses. As a fuel, hydrogen has several obstacles that need to be overcome.

As a gas, it has a very low energy density, can diffuse through metals, and has the undesirable characteristic of making some material brittle. Stored as a liquid this is less of a problem, but storage temperatures and pressures are much more difficult to achieve than say for LNG or LPG.

A new power source that is beginning to be discussed is the molten salt nuclear reactor. If prejudice against nuclear power can be overcome, the MSR nuclear power system has much to recommend it. It can be installed in a newbuilding with sufficient fuel to last for the whole lifetime of the ship. Freeing up space for cargo that would have otherwise been sued for fuel and eliminating the need to take bunkers thus avoiding any fluctuation in fuel prices and imposing no limitations on service speed.

But these are the future, and in the meantime, ship operators have to work with what is available and affordable. LNG which produces around 15-20% less CO2 than fuel oils is beginning to be used in an increasing number of ships. Once confined to LNG carriers and ferries, LNG is now used on almost all ship types albeit with a fairly small reference base at the present. Containers, bulk carriers, tankers, car carriers and cruise ships are all sectors where LNG is now used as a fuel.

Although a fossil fuel, LNG is chemically identical to methane produced from renewable sources and can also be synthetically produced. The same is true of fuel oils and numerous vessels have made voyages wholly or partially using fuels produced from renewable sources. Some operators are even offering carbon neutral carriage of goods to cargo owners concerned about projecting a ‘green’ image.

Currently the IMO’s EEDI and EEXI rules do not take account of bio and synthetic fuels in calculating ships’ ratings. If this were to change it is very likely that bio and synthetic fuels would be much more readily embraced by operators as there is practically no need to change existing procedures besides taking a little care over monitoring ignition characteristics and ensuring fuels are not mixed.

The argument that fuels from renewable sources although chemically identical to fossil fuels are carbon neutral is one that not all stakeholders are willing to accept. There will no doubt be pressure from the suppliers of such fuels, but it is not a battle for which the outcome can be predicted.

Methanol is another fuel that is gaining acceptance although it too is not emission free and merely reduces the amount of carbon emissions. Its benefits include not requiring refrigerated storage and requiring in most respects treatment similar to that of oil fuels.

So far methanol use has been confined to methanol carriers where the fuel is taken from the cargo, and ferries where methanol is supplied from shore, but Stena and Maersk have both announced plans for other ship types fuelled by methanol to be on the water in 2023. If adopted on a wider scale, methanol supply could be rapidly rolled out using the tanks and bunker barges already used for oil fuels.

LPG is another niche fuel that is growing in acceptance although so far only for use on LPG carriers. LPG has some advantages over LNG in that it requires less refrigeration and can even be stored under pressure at ambient temperatures. Widely used as a fuel in many fields, LPG already has a global infrastructure in place but that would need to be scaled up if it becomes more used in marine.

Some see LNG, methanol, LPG and bio and synthetic fuels only as a step towards a fully carbon free future but others disagree saying that shipping needs a diversified fuel choice because of the volumes involved.

The future fuel that is seen as being the most promising is ammonia. It is entirely carbon free although its nitrogen content will combine with oxygen when combusted producing NOx and other compounds that are considered as harmful. This would mean that a ship fuelled by ammonia would likely need a Selective Catalytic Reduction (SCR) system installed but many already have that.

Ammonia is not yet an accepted fuel and there are issues to overcome before even the engine makers consider they have a commercially viable product. Once again, the year 2023 is most frequently mentioned and although it may be possible to have the first engines in service at that time, the likelihood is that it will be a few years later when ammonia-fuelled ship orders are seen as nothing unusual.

Ammonia requires much the same storage and fuel systems onboard as LNG and as LNG-fuelled ships multiply in number, the same ship designs could equally be used for ammonia fuel as LNG. It would be possible for a ship with a dual-fuel engine to run on oil fuel (synthetic, bio or fossil sourced), LNG or ammonia. However, ammonia and LNG could not be stored in the same tanks simultaneously because of the different temperatures involved.

From an operational point of view – especially with the IMO’s Carbon Intensity Index likely to be arriving soon – emission recording and verification will become more complicated. This could mean that exhaust analysis systems will become more common and possibly even mandatory. They would need to be able to measure SOx, NOx and CO2 emissions and maybe even other components such as methane released due to methane slip when an engine is running on an LNG type fuel.

Because of the build time for ships being around two years most ships ordered now will need to be oil or LNG fuelled, their engines could be adapted later to run on other fuels but space for storage and fuel transfer would need to be designed in. After 2023, attitudes may begin to change, and owners become more adventurous, but it will possibly be another 5 to 10 years before real changes begin to be noticeable with regard to ship numbers.

Thereafter, assuming no geopolitical influences, things will depend more on the financial incentives – or penalties – applied to encourage a switch away from fossil fuels. Some believe that a regional approach to emissions from shipping is an inevitable consequence of the failure of agreements being reached across the IMO’s member states on the pace of change.

Currently the destination is clear but the route to getting there has many options.

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