In recent years, methanol has gained attention as a sustainable maritime fuel. Its liquid form, production versatility from renewable sources, and potential to reduce greenhouse gas emissions make it a compelling alternative to Fossil fuels for powering Ships.
Methanol As Maritime Fuel
Methanol, also known as methyl alcohol, is a clean-burning fuel derived from natural gas, biomass, or even captured CO2. Its high octane rating makes it efficient for marine engines, reducing emissions of sulfur oxides (SOx) and particulate matter and soot compared to traditional fossil fuels.
Properties
Technical Specification/Details
Boiling point: With a boiling point of 64.7 degrees C, it is a liquid at room temperature and does not require to be compressed and cryogenically stored unlike LPG, LNG, Hydrogen etc.
Density: It has a density of approximately 0.79 g/cm³ at 20°C. Methanol is thus lighter than water
Solubility: Methanol is highly miscible meaning it will readily dissolve in seawater in case of a spill.
Flashpoint: It has a low flash point of 11 DegC making it a highly flammable fuel and requiring a higher degree of safety in storage and handling.
Energy Density: Methanol (CH3OH) is a simple alcohol with a lower energy density (5.5 kWh/kg) compared to Heavy fuel oil (HFO) (12.6 kWh/kg). This means we need to burn more than twice as much quantity of methanol compared to HFO to achieve the same energy output. The implications for storage tank capacity still need to be evaluated for each vessel type when considering a switch to methanol.
Energy/Performance Efficiency: While energy density is lower, methanol offers near-complete combustion, leading to potentially improved engine efficiency compared to HFO. This can partially offset the difference in energy density and may require more frequent bunkering depending on voyage lengths.
Emission Profile
The carbon footprint of methanol depends on the feedstock and the production pathway, taking into account all the emissions caused directly by the supply chain and by energy and materials used in the supply chain.
The GHG intensity of methanol can vary depending on several factors such as:
- Feedstock (Natural gas/Biomass/Coal/Captured CO2 etc.)
- Production process
- Carbon capture and Utilisation
- Life Cycle Assessment (Extraction, Production, Transportation, Storage and combustion).
Based on existing Life Cycle Analysis, Methanol typically shows a better overall environmental performance compared to HFO. Methanol’s low carbon content, better combustion efficiency and potential for renewable feedstocks give it a lower GHG Intensity than HFO.
Types
The two most used types classified on the method of production are:
- E-Methanol: Produced using renewable electricity, E-methanol offers a carbon-neutral alternative, crucial for meeting stringent environmental regulations. It is synthesized through the electrolysis of water to produce hydrogen, which is then combined with CO2 to form methanol. E-methanol promises zero net carbon emissions when sourced from renewable energy.
- Bio-Methanol: Made from biomass feedstocks such as agricultural residues, forestry waste, or dedicated energy crops, Bio-methanol reduces lifecycle greenhouse gas emissions and promotes sustainability. It can be produced through gasification and subsequent synthesis processes, ensuring a renewable and environmentally friendly fuel option.
Technology Readiness
All major Engine makers including MAN ES, Wartsila and WinGD, have designs for 2-stroke and 4-stroke Engines capable of using Methanol as fuel. All are dual-fuel engines, capable of using marine diesel, marine gas oil or fuel oils as a fuel. These engines also require a diesel or fuel oil pilot fuel injection when using methanol fuel.
MAN ES calculations suggest that the pilot fuel will be between 1% and 3% of the fuel mix, depending on engine load and the inclusion of optimized methanol-diesel share with Port Fuel Injection (PFI) technology.
Fuel Injection and Mixing
Methanol is injected into the combustion chamber alongside air. The amount of methanol injected is typically a significant portion of the total fuel input, often around 60-80% by energy content, depending on engine design and operational parameters.
Compression and Ignition
The engine compresses the air-methanol mixture. Ignition can occur through various methods:
- Spark Ignition: Similar to gasoline engines, where a spark plug ignites the mixture.
- Compression Ignition: Utilizing the high compression temperatures to ignite the mixture without a spark plug, akin to diesel engines.
Performance and Efficiency
Methanol’s high octane rating (typically around 110-130) improves combustion efficiency compared to diesel. This leads to reduced emissions and burns more cleanly, contributing to lower greenhouse gas emissions.
Flexibility and Adaptability
Dual fuel systems allow ships to switch between methanol and other fuels based on availability, cost, and environmental regulations. This flexibility is crucial for complying with emission control areas (ECA) and achieving operational efficiency.
The Dual-fuel methanol engine is notable in the containership segment of Maersk line, Hyundai, CMA CGM, Cosco etc. for having made the strategic decision to move towards methanol fuels.
MAN ES has MAN B&W ME-LGIM engines on 20 vessels that are currently operational, including several methanol carriers that can use their cargo as fuel and has a big orderbook of new buildings. WinGD has announced one of its first two-stroke methanol dual-fuel orders including a 90-bore engine on 4 container ships.
Operational Considerations
Storage and Handling
Due to its highly corrosive nature, it must be stored in specialized bunker tanks. The common storage tanks include:
- Integral Fuel Tanks: The integral fuel tank is the same kind of tank as normally used for marine gas oil; however, the methanol fuel tank should be surrounded by cofferdams and its ullage space must be filled with Inert gas to prevent fire. Cofferdams are not required below the water line, because it is non-toxic to aquatic life and biodegradable.
- Independent Fuel Tanks: Independent tanks are self-supporting, do not form part of the ship´s structure and are not essential to the hull strength. Independent tanks can either be positioned above the deck or below the deck. When positioned below the deck, the space in which the tank is placed is called the fuel hold space.
- Portable Fuel Tanks: A portable tank is like an independent tank with the exception that it can be easily connected and disconnected from the ship´s systems and that it can easily be installed on- and removed from the ship.
Availability and Costs
The Asia-Pacific region is the largest producer of Methanol with China, India, and Indonesia leading the charge. The USA is also a significant producer. Germany and the Netherlands have the most production capacities in Europe while in the Middle East; Iran, Saudi Arabia and Oman are the major producers.
The cost of e-methanol depends to a large extent on the cost of hydrogen and CO2. The cost of CO2 depends on the source from which it is captured, e.g. from biomass, industrial processes or DAC. Methanol as a marine fuel is priced at approximately 350 USD/MT presently.
Prices can vary between regions due to transportation costs, local regulations, and infrastructure availability. For ship propulsion, it need not be its purest form and can be blended down with 25% water injection making it cheaper.
One way to accelerate decarbonization is to implement “green corridors”, i.e. specific trade routes between major port hubs where zero-emission solutions are supported. These corridors would ideally be large enough to include all relevant value-chain actors, such as fuel producers, cargo owners, and regulatory authorities.
They would provide fuel producers with offtake certainty and send strong signals to vessel operators, shipyards, and engine manufacturers to ramp up investment in zero-emission shipping, making the risks more acceptable for all involved.
As of 2019 data, the Australia-Japan Iron Ore route trades 111 Bulkers, burning over 5 lakh Metric tons of Fuel Oil, equalling 1.7 million MT of CO2 Emissions! It would take about 40 zero-emission vessels to decarbonize all iron ore trade between Australia and Japan.
The Asia-Europe containership route traded 24 million TEUs, burning 11 million MT of Fuel! The pipeline of announced green-fuel projects is sufficient to supply 50 zero-emission new-build vessels, which would be required to replace ageing vessels on this corridor.
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Source: MarineInsight
