On 13 April 2018, the International Maritime Organization (IMO) adopted resolution MEPC.304(72) on Initial IMO Strategy on reduction of GHG emissions from ships.
The initial strategy refers to a range of candidate short-, mid- and long term measures that will be considered by IMO.
According to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, policy measures fall into five broad categories (IPCC 2014):
• Regulatory approaches (e.g. set a limit or standard).
• Economic instruments (e.g. Market based measures (MBMs) like subsidies, levies, credits or allowances).
• Information policies (e.g. exchange of best practices, technical cooperation)
• Government provisions and procurement (e.g. procurement of low-carbon fuels for government-operated vessels )
• Voluntary action (e.g. rewarding good performers, port incentives).
Furthermore the measures can be specific (e.g. set a maximum carbon content of marine fuels) or goal based (e.g. setting a carbon intensity goal for ships). In case of goal based measures, it will be up to the shipowner to decide on how to achieve the requirement by either retrofitting the ship to be more energy efficient, or adopting fuel-efficient operations, innovative solutions and alternative fuels. The technical and operational solutions may include:
• Hull Form Optimization (e.g. Optimizing Ship Particulars, Minimizing Hull Resistance and Increasing Propulsion Efficiency)
• Energy-saving Devices (e.g. Propulsion Improving Devices, Skin Friction Reduction)
• Renewable Energy (e.g. Solar panels, wind propulsion)
• Structural Optimization and Light Weight Construction (e.g. Use of Higher Strength or composites)
• Advanced Machinery Technology (e.g. Engine Energy Efficiency Enhancements and Performance
Measurement and Control, Waste Heat Recovery, Variable Speed Motors)
• Alternative fuels (e.g. LNG/LPG, ethanol/methanol, Hydrogen, ammonia, Bio-fuels)
• Efficient Operation (e.g. Voyage Performance Management, Hull and Propeller Condition Management)
Concerns have been expressed that the improvement of ship design and operation through the deployment of energy efficient technologies may not be enough to meet the targets, and significant energy switching from fossil fuels to alternative low carbon energy including renewable energy in the future is needed. Some alternative fuels are briefly discussed below:
1. LNG/LPG:
The use of natural gas as a ship’s fuel is not new. The first LNG fueled LNG carrier, the ABS classed Methane Princess, was entered into service as early as 1964. Some of the challenges include:
• Bunkering
• Methane Slip
• Complex Systems
• Storage and distribution network.
According to the main engine manufacturers, CO2 emissions will typically reduce by as much as 20-25%.
LPG as fuel on the other hand is a relatively new endeavor for the shipping sector. There are currently several projects with Approval In Principle (AIP) from major classification societies with at least a couple in progress in Greece for the retrofit to LPG carriers.
Due to the wider potential availability of LPG bunkers and easier handling and storage, boom in shale gas exploration and potential price to rival HFO, a LPG fueled vessels expected to materialize in the near future. Some of the challenges include:
• Bunkering
• Complex Systems
• LPG vapor is heavier than air and it moves downwards
• Need for SCR for NOx Tier III compliance
According to the main engine manufacturers, CO2 emissions will typically reduce by as much as 20%
2. Ethanol/Methanol:
Experience operation of methanol in marine engines is small due to the limited number of applications. Methanol’s heating value is half than diesel, thus requiring almost double storage volume or more frequent bunkering. Also, it might be required to install different injectors to cope with the increased fuel flow demand. Methanol is more corrosive than conventional fuels so the material selection should be considered or special coatings may be required.
Ethanol has not been used on ships yet. However, it has been used in diesel engines in the transport sector. Its properties, such as energy density, viscosity, lubrication ability and flash point are similar to methanol, is also sulphur-free, corrosive to some materials and it dissolves quickly in water. However, is not classified as toxic to humans.
Type of fuel | Lower calorific value (kJ/kg) | Carbon content |
CF (t-CO2/t- Fuel) |
Liquefied Natural Gas (LNG) | 48,000 | 0.7500 | 2.750 |
Methanol | 19,900 | 0.3750 | 1.375 |
Ethanol | 26,800 | 0.5217 | 1.913 |
CO2 emissions will typically reduce due to the lower conversion factor CF but both fuels have relatively low calorific value.
3. Hydrogen:
So far, liquid hydrogen has not been used as marine fuel. A fuel cell will convert the hydrogen which is stored in pressurized tanks to electricity for propulsion and electric power on board. One of the technical challenges is to maintain the liquid hydrogen fuel at minus 253 degrees to keep it from evaporating. Hydrogen is also a very explosive gas, and protection against gas leaks is an important part of the safety requirements for the fuel. Much R&D work is being done towards generating hydrogen in a sustainable manner (e.g. using excess electricity from wind farms).
4. Ammonia:
Ammonia is produced on a large scale worldwide for the fertilizer industry. Technology for production, storage and transportation both on land and at sea is mature. Ammonia can be used as the hydrogen source for fuel cells. Use of ammonia as fuel for internal combustion engines (ICE) is possible and has been demonstrated with both gasoline and with diesel engines. In both cases a pilot fuel was needed in conjunction with the gaseous ammonia. When ammonia is burned in an internal combustion engine CO2 is not emitted, but some NOx. However as with hydrogen, at present large scale production of ammonia does leave a carbon footprint.
* Director, Business Development, ABS