A new report addressing the reduction of emissions from the global maritime sector by Longspur Research analyzes the benefits and drawbacks of new technologies and fuels to achieve shipping’s decarbonization.
Methanol
Methanol has been identified by the IMO as a fuel that delivers climate benefits today. Methanol is four parts hydrogen, one part carbon and one part oxygen and is typically produced from natural gas through reformation of the gas with steam to produce syngas and then converting and distilling the syngas to produce methanol.
This is known as ‘grey’ methanol and today accounts for 95% of total methanol used in the shipping industry. In saying this, grey methanol produces 80% less NOx, 99% less SOx, 95% Particulate Matter (PM) and approximately 20% less CO2 than HFO on a tank-to-wake basis according to MAN Energy Solutions.
Batteries
All-electric marine vessels hold multiple advantages as they are quiet, environmentally friendly without any emissions or risks of oil spills and have reduced maintenance costs. However, using batteries on ships can also be a difficult market with multiple challenges such as:
- Limited range to the size of the battery bank, where the weight can add up quickly and beyond the maximum carrying weight of the vessel.
- Range can be improved by using a generator, however, speed is limited by the size of the battery charger and the generator may be a source of emissions.
- Batteries systems with electronic components on a boat are prone to corrosion and need to prove themselves to be safe and reliable in a hostile environment.
- Deep discharging of batteries can cause damage and failure that is not easily diagnosed.
- Lithium-ion batteries are particularly susceptible to thermal runaway where overcharge, over-discharge, over-temperature, short circuit, crush and nail penetration may all result in a catastrophic failure, including the pouch rupturing, the electrolyte leaking, and fire which is difficult to extinguish.
- Charging is affected by being at the “end of grid” and often in built up areas
As it stands today with the current battery technology, all electric vessels are primarily used for shorter distances in harbours and coastal shipping and therefore account for a minor proportion of the global marine market.
A battery propulsion solution is the most efficient at 68% if the power was provided by a zero-carbon source
said the report.
Wind-assisted ship propulsion
Wind-assisted ship propulsion (WASP) enables ships to reduce fuel consumption through the use of technologies that are able to utilize the wind to propel a ship forward. Unlike some alternative fuels, WASP technologies are not dependent on new infrastructure for storage, use a cost-free energy source and have technologies already developed that can be adopted at scale today.
The ability for ship operators to flick between conventional or alternative fuels and WASP in times of high wind speed has the potential to be an attractive fuel cost saving method as well as having a positive effect on the IMO energy efficiency index EEDI.
Modern WASP technologies that practical for deep sea shipping come in the form of wing sails, kite sails deployed in high altitude wind, Flettner rotors and Ventifoils.
Low carbon liquid fuels
The key long haul shipping solutions are liquid fuels of one form or another. The key contenders are hydrogen, ammonia, methanol and biomethane.
All these fuels can be used in reciprocating engines with greater or lesser degrees of modification, normally to the fuel delivery systems.
The major manufacturers are working on methanol and ammonia ready engines with methanol units already in service. Ammonia engines remain in development and are only expected in 2025.
LNG
LNG is considered by many in the shipping industry as the ideal transitioning fuel for shipping decarbonisation. Whilst natural gas is a fossil fuel, it offers a lot of environmental benefits when compared to traditional shipping fuels and can be deployed today at a fraction of the cost of alternative low carbon green shipping fuels.
Its growing popularity amongst shippers is largely due to its ability to minimise the long-term impact of GHG emissions and meet short term regulatory requirements implemented by the IMO.
Additionally, moving to LNG reduces SOx emissions and particulate matter by 90% and NOx emissions by 80% when compared to HFO and will enable vessels to reduce their EEDI rating and Carbon Intensity Indicator by c.20%.
Biofuels
The most suited form of biofuels for the shipping industry are hydrotreated vegetable oil (HVO), fatty acid methyl ester (FAME) otherwise known as biodiesel and bio-LNG. It is important to considered that each feedstock differs in its GHG emission reduction capabilities with Lifecycle GHG reductions in the range 20-90% are typically reported for different biofuels, making many of these poor low carbon solutions.
HVO as an alternative shipping is considered a ‘drop in’ fuel meaning it is a direct substitute for current HFO using existing petrol engines.
Whilst untreated vegetable oils are not practical as a drop in fuel based on the fact, they reduce the engine lifespan due to build-up of carbon deposits and damage to engine lubricant, HVO is a much higher quality fuel having undergone the process of removing the oxygen using hydrogen.
FAME or biodiesel is not considered a drop in fuel but instead can be blended with conventional fuel making it an ideal transitional fuel but long-term usability in deep sea shipping is unlikely.
Hydrogen
Creating ‘blue’ hydrogen is expensive and does not completely eliminate emissions. Green hydrogen is produced by a process called electrolysis where water is split into hydrogen and oxygen using renewable electricity.
The biggest challenge for using hydrogen for long distance shipping is how difficult it is to store in comparison to not only the HFO but other potential fossil free fuels being considered.
Hydrogen cannot simply replace current bunker fuel in the current system as in order to store it on a ship as a liquid, it will need to be frozen to temperatures of around minus 253oC requiring heavy cryogenic tanks that take up precious space.
Ammonia
One of the advantages ammonia has is it is already a traded commodity, used to produce fertilizer. This means that the infrastructure and procedures associated with transporting ammonia are already in place as ammonia is frequently loaded and unloaded from gas terminals onto ships and vice versa.
Additionally, ammonia can be stored as a liquid at minus 33 degrees Celsius at ambient pressure on board the vessel and at port site facilities without the need for cryogenic tanks.
However, ammonia has never been bunkered.
EXPLORE MORE AT THE METHANOL RESEARCH
