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Insurer weighs pros and cons of methanol and ammonia as eco fuel
来源：shippingazette 编辑：编辑部 发布：2023/01/30 14:41:00
LONDON marine insurer Standard Club has weighed the pros and cons of methanol and ammonia as eco marine fuel, and found pluses and minuses for both, reports Athens' Safety4Sea.
As Standard Club says, the UN's International Maritime Organisation (IMO) has set decarbonisation goals.
#1 Methanol has several benefits, including liquid at ambient temperatures, so no need to heat or cool. It is easier to store and handle than cryogenic fuels. Possible to convert existing engines from conventional fuel to methanol.
Relatively minor modifications are needed to existing storage and bunkering facilities. It is already widely traded, well-understood and readily available in some ports for bunkering.
It is watersoluble and biodegradable, with a lower impact on the environment if a spill happens. Comparatively more energy-dense than hydrogen and ammonia. It is a clean burning fuel with low levels of sulphur oxide (SOx), nitrous oxide (NOx) and particulate matter.
But methanol has its problems: Production is still mainly via processing natural gas (grey methanol) or coal (brown methanol), limiting the reduction of CO2 emissions. Only when methanol is produced using renewable sources like biomass, and if the power used to produce it comes from renewable energy, it is considered to be green methanol.
Lower energy density than conventional fuel oil. Large fuel volume is almost 2.5 times fuel oil, so it requires larger storage tanks and/or more frequent bunkering. It has a low flash point of well below 60C is a fire risk, requiring extra fire prevention measures when handled and stored.
It is toxic if inhaled, ingested or handled. Increased corrosion risks Apart from larger volume of fuel tanks, additional cofferdams will be needed to prevent any potential leak into machinery spaces.
#2 Ammonia also has its problems. Processing may influence its cost competitiveness. It challenges include its toxicity. Being extremely soluble, even at extremely low concentrations, ammonia can be absorbed by body fluids (sweat, tears, saliva) and may cause severe chemical burns. Therefore, using ammonia fuel will require additional safety systems.
Ammonia also poses enhanced corrosion risk of certain metals such as copper, brass and zinc and various alloys. Although ammonia is commonly carried as a cargo, it is still in the early stages of development as a fuel the regulatory frameworks are still being worked out. The IGF Code currently does not provide prescriptive requirements to cover toxic fuels like ammonia.
Ammonia's lower efficiency means much more storage capacity will be required on board. The additional space for fuel may require larger vessel sizes, decreased cargo space or more frequent bunkering.
Tanks will need to be designed for temperature and/or pressure control if ammonia is stored in a refrigerated condition, as ammonia continuously evaporates and generates boil-off gas due to heat gain, which increases pressure in tanks if not managed. This storage at low temperatures will require energy.
Ammonia burns more slowly than other fuels and has higher autoignition temperature than conventional fuel oil. This means that sustaining combustion once it gets started is going to be more difficult.
While carbon-free, ammonia contains nitrogen, and burning it will result in nitrogen oxide (NOx) and nitrous oxide (N2O) emissions. GHG impact of N2O emissions is nearly 300x greater than CO2.
As Standard Club says, the UN's International Maritime Organisation (IMO) has set decarbonisation goals.
#1 Methanol has several benefits, including liquid at ambient temperatures, so no need to heat or cool. It is easier to store and handle than cryogenic fuels. Possible to convert existing engines from conventional fuel to methanol.
Relatively minor modifications are needed to existing storage and bunkering facilities. It is already widely traded, well-understood and readily available in some ports for bunkering.
It is watersoluble and biodegradable, with a lower impact on the environment if a spill happens. Comparatively more energy-dense than hydrogen and ammonia. It is a clean burning fuel with low levels of sulphur oxide (SOx), nitrous oxide (NOx) and particulate matter.
But methanol has its problems: Production is still mainly via processing natural gas (grey methanol) or coal (brown methanol), limiting the reduction of CO2 emissions. Only when methanol is produced using renewable sources like biomass, and if the power used to produce it comes from renewable energy, it is considered to be green methanol.
Lower energy density than conventional fuel oil. Large fuel volume is almost 2.5 times fuel oil, so it requires larger storage tanks and/or more frequent bunkering. It has a low flash point of well below 60C is a fire risk, requiring extra fire prevention measures when handled and stored.
It is toxic if inhaled, ingested or handled. Increased corrosion risks Apart from larger volume of fuel tanks, additional cofferdams will be needed to prevent any potential leak into machinery spaces.
#2 Ammonia also has its problems. Processing may influence its cost competitiveness. It challenges include its toxicity. Being extremely soluble, even at extremely low concentrations, ammonia can be absorbed by body fluids (sweat, tears, saliva) and may cause severe chemical burns. Therefore, using ammonia fuel will require additional safety systems.
Ammonia also poses enhanced corrosion risk of certain metals such as copper, brass and zinc and various alloys. Although ammonia is commonly carried as a cargo, it is still in the early stages of development as a fuel the regulatory frameworks are still being worked out. The IGF Code currently does not provide prescriptive requirements to cover toxic fuels like ammonia.
Ammonia's lower efficiency means much more storage capacity will be required on board. The additional space for fuel may require larger vessel sizes, decreased cargo space or more frequent bunkering.
Tanks will need to be designed for temperature and/or pressure control if ammonia is stored in a refrigerated condition, as ammonia continuously evaporates and generates boil-off gas due to heat gain, which increases pressure in tanks if not managed. This storage at low temperatures will require energy.
Ammonia burns more slowly than other fuels and has higher autoignition temperature than conventional fuel oil. This means that sustaining combustion once it gets started is going to be more difficult.
While carbon-free, ammonia contains nitrogen, and burning it will result in nitrogen oxide (NOx) and nitrous oxide (N2O) emissions. GHG impact of N2O emissions is nearly 300x greater than CO2.