Is methanol the alternative to diesel oil in shipping?
In 2018, the 173 countries affiliated to the International Maritime Organisation (IMO) agreed that the total CO2 emissions from international shipping should be halved by 2050, compared to 2008. Hence all efforts are focused on alternative fuels, of which methanol is the biggest contender for becoming a good alternative to diesel oil in the short term.
What is methanol?
Methanol is alcohol in its most basic form and not suitable for consumption. It is one of the most widely used raw materials in the chemical industry. Almost half of all methanol is used to produce formaldehyde, which is a raw material for adhesives, paint products and plastics, among other things.
In its pure form, it can be used as a fuel and in the production process of biodiesel (vegetable diesel oil). To date, most methanol is still extracted from natural gas and coal (black methanol), but biomethanol is on the rise. Biomethanol can be produced:
- from renewable raw materials such as biomass
- with green power, with which you can make hydrogen and extract the CO2 from the biomass
This biomethanol does not differ chemically from black methanol, but because the CO2 that is released after combustion has been removed from the biomass, CO2 emissions are zero on balance.
What are the advantages of methanol?
No sulphur, less nitrogen oxides and particulate matter
Due to the strong focus on CO2, you would almost forget that the combustion of diesel oil also involves the release and emission of sulphur oxides (SOx), nitrogen oxides (NOx) and particulate matter (PM). A major advantage of methanol is that it does not contain sulphur. Therefore, the combustion does not involve the release of sulphur oxides, nor particulate matter. The nitrogen oxide content is expected to be lower as well. However, that also depends on the engine settings.
Relatively safe fuel
Methanol is a relatively safe fuel, which is liquid at ambient temperature and can be bunkered just like diesel oil. Since the temperature at which methanol starts to evaporate (the flash point) is lower than that of diesel oil, additional regulations apply. So that is something to take into account, but does not stand in the way of large-scale storage & use.
Readily biodegradable
Methanol is readily biodegradable in water and therefore much less harmful to the environment than petrol, diesel or heating oil. Methanol discharges at sea spread faster and aquatic plants and bacteria break it down biologically easily and quickly, without residue.
Good to use in an internal combustion engine
Another major advantage of methanol is that this fuel can be used well in an internal combustion engine. However, the properties of methanol differ considerably from diesel oil. Certain parts of existing diesel engines therefore have to be adapted before you can use them.
Just like with a petrol engine, a spark is needed to ignite the methanol. That ignition energy can be obtained by, for example, injecting a small amount of diesel oil, which is called pilot injection. Other fuels, with just as low a self-ignition temperature as diesel oil, can also be used for this. Given the high reliability of fuel injectors, many engine manufacturers are likely to opt for this method.
As mentioned, methanol does not contain sulphur, and less nitrogen oxides and particulate matter are released during combustion than with diesel oil. The little particulate matter that is emitted comes from the lubricating oil consumption of the engine and from the pilot injection. It therefore does not come from the methanol, which burns cleanly, which also means that the exhaust gas after-treatment can be less complex and smaller than with diesel engines.
As a proof of concept, we at Pon Power had a Cat engine run on methanol in 2020. It was a great success. The concept was not intended to be marketed, but it helps us better understand how it works and what challenges we still face.
What are the disadvantages of methanol?
Lower energy density than diesel oil
A major drawback of methanol is its lower energy density. It weighs almost the same as diesel oil, but contains slightly less than half the energy. Consequently, you need more than twice as much fuel for the same distance. So you have to take this into account with regard to the bunker size and weight.
Other safety instructions
Due to its lower flash point (11°C versus 52°C for diesel), methanol is subject to different safety regulations for bunkering, storage and the fuel delivery system. The entire fuel system of a ship must therefore be adapted or designed for the use of methanol. There are also stricter regulations for, among other things, ventilation and vapour detection.
Methanol vs other biofuels and batteries & fuel cells
Methanol has the best chance of succeeding
It is not so much about whether methanol is better or worse than other biofuels or batteries. There will inevitably be applications where those options are better suited. But when comparing the current alternatives and carefully looking at all facets, such as motor fuel use, safety, bunkering & storage options and emissions, we believe that methanol has the best chance of succeeding for maritime applications, because of the properties of this alternative fuel:
- liquid
- CO2 neutral
- biodegradable
- excellent motor fuel
Biofuels
Fuels made from vegetable materials, such as biodiesel (FAME: Fatty Acid Methyl Ester) and HVO (Hydrotreated Vegetable Oil), share more or less the same properties as fossil diesel oil. One advantage of biodiesel and HVO is that the engine and fuel storage do not have to be adapted for these fuels, provided the fuel system seals are suitable. The disadvantages compared to methanol are the particulate emissions and that you need biomass or vegetable oils to produce it, whereas you can also make methanol through electrolysis and CO2.
Biodiesel
Due to the legal blending obligation, a small percentage of biodiesel or HVO is added to the fossil diesel oil. However, biodiesel is highly hygroscopic: it attracts moisture that is absorbed into the biodiesel. This causes bacterial growth when it is stored in the fuel bunker for a longer period of time. This in turn forms flakes that can clog the fuel filters.
HVO
You do not have that problem with HVO. It is refined from organic components, contains no fatty components and is not hygroscopic. HVO can be mixed in and thus you meet the mixing obligation, but it can also be used pure in most engines.
BioLNG
BioLNG (liquid green gas) can be used for gas/diesel Dual Fuel or gas engines. This fuel mainly consists of methane gas that comes from the fermentation of biomass. To store it, a large, well-insulated storage tank is required and the equipment to vaporise the BioLNG again. The cost of such a system is high, and in addition, you must have the space for it.
Hydrogen
Carrying enough hydrogen on a ship is only possible if it is stored in liquid form or under very high pressure. To liquefy and keep it, store it refrigerated below -254°C. For comparison: LNG must be cooled to -164°C and also supplies approximately twice as much energy per (liquid) m3. The storage of hydrogen can therefore stand in the way of its use for ships. But for applications where this is not a problem, it can also be a CO2-neutral solution. Major adjustments to the combustion engines are, however, required, because hydrogen burns more easily and faster than diesel oil, but that is something that is being looked into.
Batteries
Batteries for primary marine propulsion can only be used for very specific applications. The distance to be covered must be limited or it must be possible to recharge or exchange the batteries in the meantime. Given the size of the required capacity, batteries can quickly become too expensive and heavy.
One option, for example, to cover a small route without emissions, is to install an acceptable amount of batteries, which can also be used when the ship is stationary, instead of the auxiliary generator. This gives the luxury of silence.
Fuel cells
Another option is to use fuel cells. However, these are still very expensive compared to the same power of engines and also require an all-electric or hybrid propulsion line.
The methanol engine is coming
Diesel engines have been in use for more than a century and are still being developed for more power, higher efficiency & reliability and therefore lower costs. You do of course want the same for methanol engines. Caterpillar is currently working hard on developing and testing new engines.
As things stand and with current progress, we estimate that Pon Power will be able to offer methanol engines within a few years. Installing these engines in existing ships will require a significant retrofit in terms of the fuel storage and supply system.
Methanol important alternative fuel in shipping
Since shipbuilders look about 10 years ahead and expect that methanol will gradually become one of the main alternative fuels in shipping, they are already taking this into account. This includes the fact that different safety regulations apply compared to diesel.
These regulations, the lower energy density and its consequences have a major impact on the design of the entire fuel system, ranging from storage to engines.
The new methanol engines and the new ships on the horizon will make a noticeable contribution to reducing CO2, sulphur, nitrogen oxides and particulate emissions. It therefore seems that methanol is indeed the alternative to diesel oil in shipping.
Facts & figures
100 jaar
It has taken us a century to refine diesel technology to what it is today. The transition to methanol will take several years.
2020
In 2020, Pon Power ran a Cat engine on methanol as a proof of concept.
2050
By 2050, total CO2 emissions from international shipping must be halved.
2,2x
The storage of methanol requires 2.2 times more space than diesel oil and therefore weighs twice as much.
11°C
Methanol has a lower flash point than diesel oil: 11°C vs 52°C.
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