Shipping & Environmental Air Pollution
As maritime transportation plays an important role for world sea trade its contribution to air pollution and climate change cannot be brushed aside. The current population of the world merchant fleet of 100 gross tonnage and above is about 117,000 vessels and the total gross tonnage is 1.36 billion. Annual growth was 4.6 % by number of vessels and 5 % by gross tonnage in the period 2008 to 2018 . During the period from 2007 to 2012 average annual maritime fuel consumption ranged between 250 and 325 million tonnes and average annual emissions of sulphur oxides (SOx), nitrogen oxides (NOx) and carbon dioxide (CO2) were 11.3 , 20.9 and 1016 million tonnes respectively. Maritime CO2 emissions by the year 2050 are projected to increase by 50 – 250 % as compared to 2012 .
LNG Carriers & Decarbonization lead to Higher Shipping Costs
Generally liquified natural gas (LNG) carriers have a capacity of 174,000 cbm. One LNG carrier namely BW Cassia, is an interesting case study , being equipped with a small scrubber for carbon capture pilot project intended to capture 50 kg/h CO2 using proprietary technology. The CO2 scrubbers are huge funnels from which the exhaust is tapped of dual-fuel engines capable of burning VLSFO and LNG and propulsion shaft. The LNG cargo boil off is reliquified and returned to the cargo tank when there is an excessive pressure buildup from where it gets fed into the engine and combusted as fuel. The LNG can be directly fed into the engine from the cargo tank without any additional or separate holding tanks.The four cargo tanks can be accessed in parallel, as opposed to serially, for both cargo and fuel.The tank walls comrise of Nickel-Iron alloy having a low thermal expansion coefficient, remaining ductile and crack resistant at the cryogenic temperatures needed to store LNG (-160C).
Supply Capacity
The shipping industry is taking its foray towards decarbonization and the classification society DNV in its latest edition of Maritime Forecast sensitizes the significant technical hurdles and costs involved. Shoreside infrastructure and production has to have the capacity to supply sufficient quantities of fuel . As of now only 5.5 % of the global fleet in service can operate on alternative fuels but a third of the vessels under construction (based on gross tonnage) are designed to use alternative fuel sources. At present LNG rules the roost with around 900 ships in service and another third of current orders of 500 ships due in the near term.
Sustainable Green Fuels & Climate Change Onslaught
Keeping in view the efforts to develop many options ranging from ammonia to methanol and methane as well as fuels produced from sustainable biomass such as bio-LNG, bio-MGO, bio-methanol it is predicted that fossil-based LNG may witness a decline by the year 2050. There is a trend towards electronification which may double in the future yet lower sulfur fuels with carbon capture and storage will remain a part of the industry for years to come.Higher shipping costs are yet to be recognised in the face of the climate change onslaught.
Uncertainty of Investments in Green Technology
To add to the uncertainty surrounding alternate or green fuels pricing structure significant investments are required to achieve rapid adoption required for the maritime and shipping industry to switchover to green fuels and DNV forecasts that investments for onboard technology will range from $ 8 billion to $ 28 billion annually between 2022 and 2050. The choice of primary green fuel has to be determined as well. Investments for production and onshore infrastructure are staggering and likely to be in the range of $ 30 billion and $ 90 billion annually all the way upto 2050. Ammonia and hydrogen remain the darling green fuels of choice but developing onboard technologies , infrastructure , bunkering technology investments and challenges are expected in the handling of these fuels .Commencement of IMO’s carbon intensity regulations (CII and EEXI in 2023) may dictate future ship designing and operations.
Future Maritime Power & Green Fuels Scenario
In view of the impending diversification of marine fuels, perceived to be the inevitable choice of future maritime power and fuels , and international maritime transportation a unified fuel should be the gold standard. Climate change impact calls for an integrated abatement of SO2, NO2 and CO2 emissions .Fuels such as hydrogen, ammonia, RNG, renewable methanol, bioethanol and biodiesel need to be technologically studied in the context of key physicochemical properties, feedstock, production processes, transportation, storage, end use, combustion characteristics and emissions performance. Hydrogen and ammonia are commonly known as zero carbon synthetic fuels. Methanol (fossil/renewable) may become the future alternative fuel for global shipping instead of other carbon-neutral biofuels such as renewable natural gas , bioethanol , biogenic dimethyl ether and biodesels .
International Maritime Organization Regulating SO2 and NO2
The International Maritime Organization (IMO) has adopted various regulations and progressively amended the International Convention for the Prevention of Pollution from Ships (MARPOL) to control SOx and NOx emissions and improve ship energy efficiency . To mitigate greenhouse gas (GHG) emissions IMO adopted the Initial IMO Strategy on Reduction of GHG Emissions from Ships in the year 2018 to fulfil the responsibility of the shipping sector. The targets were overly ambitious and it was proposed to reduce the carbon intensity of international shipping by 70 % and the total annual GHG emissions by at least 50% by 2050 whilst pursuing efforts towards phasing them out as soon as possible by employing low sulphur heavy fuel oil (LSHFO), marine diesel oil (MDO), marine gas oil (MGO) or equivalent exhaust gas cleaning systems (EGCS) to control SO2 emissions. The combustion characteristics and air pollution performances of compression ignition engines using alternative fuels, which include alcohols, natural gas , biodiesel and dimethyl ether have to be extensively and scientifically studied. Liquefied natural gas ( predominantly methane), liquefied petroleum gas (predominantly propane and butane) and methanol appear to be the fuels of choice for meeting IMO Nitrogen Oxide emissions standards owing to the limitations of further improvements in engine technology and the immature status of EGCS for ship NOx emissions. In addition, two mandatory mechanisms under MARPOL Annex VI, the Energy Efficiency Design Index for new ships and the Ship Energy Efficiency Management Plan for all ships, have been introduced to improve ship energy efficiency and mitigate CO2 emissions .
Consistent Violation of MARPOL Coastline – Low Water Line
The MARPOL Convention prohibits discharge into the sea of nearly all forms of garbage including plastic. It does however, contain a specific exemption for food waste. Under MARPOL Annex V, discharge into the sea of food waste is permitted while the vessel is en route and as far as practicable from the nearest land but in any case, not less than 3 nm from the nearest land if the discharged food waste has been comminuted or grounded but not less than 12 nm for unprocessed food waste. Stricter discharge standards apply in ‘Special Areas’ however, neither China nor Australia have designated any Special Areas for the purposes of MARPOL. Countries define their baselines differently as some define the baseline for establishing the territorial sea drawn at the low-water line as stated in official charts. In a manner of speaking the normal baseline is an “outline” of a country’s coast. However, a number of countries have established baselines as straight lines between prominent coastal features and others claim “archipelagic status” with baselines joining outlying islands. Such countries’ baselines can therefore lie many nautical miles off their coasts.
Emission Inventories & Life Cycles
Recent studies have reviewed the possible decarbonization pathways and the CO2 abatement potential of alternative marine fuels such as LNG, methanol, biofuels, hydrogen and ammonia being considered as 20 – 100 % with the exact value hinging upon fuel type. LNG is propagated as an alternative fuel in shipping sector under the regulations of MARPOL. The life-cycle emission inventories of LNG and HFO for two ships operating in the Taiwan Strait were conducted as a case study and the promising future of LNG as an alternative fuel on board was highlighted. Findings indicated it being a cost-effective option to phase out fuel oil and making the transition to LNG and methanol earlier.However, the application of biofuels in the shipping sector is not advisable due to limited supply and being less competitive compared to other energy sectors. The CO2 abatement capabilities of LNG are not sufficient to deliver the necessary climate impact. LNG remains an alternative intermediate solution with a limited window of opportunity.Hydrogen, methanol and ammonia are recognised as superior options from a socio-economic cost perspective once costs are rationalised. Battery storage is only an option for short range transportation. In terms of air pollution methanol performs similarly to LNG yet better than conventional petroleum fuels. At this stage more types of feedstocks, blending, comparative fuels and pollutants need to be covered in further studies.
Electro Fuels Available Options
Electrofuels, which are carbon-neutral synthetic fuels produced from CO2 and water by storing electricity from renewable energy sources, could be used in combustion engines and may not require significant investments in new infrastructure. However, the production costs of electrofuels were found to be higher than fossil fuels and biogenic fuels. There is no readily available fuel option for the mitigation of ship emissions at present and viable alternative fuel options are constrained by constraints of feedstock supply and fuel production. More types of alternative fuels should be developed and applied in transport sectors and extensive assessment and comparison of their viability in the shipping sector made.The production and downstream use of ammonia and hydrogen may seem commercially viable yet the real challenge is in the transport, blending of various green fuels, storage and eventually distribution of hydrogen carriers.
Hydrogen
Hydrogen technology was invented in 1880 and windmills used to produce hydrogen gas for lightning purposes. Hydrogen is presently used in the chemical industry and its current day extraction is from fossil fuel and to make it environmentally friendly hydrogen production will have to be through renewable means. Generally electrolysis produces hydrogen stored in batteries with a storage time being three times that of natural gas
Green Ammonia
Green ammonia is the favoured mechanism to transport renewable energy over large distances by ships. Ammonia is highly toxic in its gaseous or liquid form and exposure to high levels of ammonia can cause death from chemical burns to the lungs. The round trip efficiency of green ammonia as a medium for transporting renewable energy needs to be first determined to establish whether it is energy efficient to use green ammonia to transport energy. Green ammonia production is a highly energy intensive process. Green ammonia can be produced by synthesis of hydrogen from water electrolysis and nitrogen separated from air in the Haber-Bosch process and approximately 13.65 kWh of green electricity produces 1 kg of green ammonia. As the efficiency of the hydrogen fuel cell is about 50 % the round trip efficiency of green electricity from green ammonia is as low as 15 % as 80-90 % of the primary green energy is lost during this process.
Battery Powered Maritime Transportation
Converting a small container ship (DWT 7000T) hauling 500 TEU’s at a speed of 15 knots into a battery powered one consumes around 15-20 tons of heavy fuel oil if powered by a low-speed diesel engine for sailing 667 km . Combined with the weight of the battery pack (almost equal to weight of 404 Tesla battery packs ) the notion of running bigger ships on battery is not appealing.
Authored by Nadir Mumtaz
Credit ; https://www.sciencedirect.com/topics/earth-and-planetary-sciences/research-vessel
https://gard.no/web/articles?documentId=34257434
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https://www.sciencedirect.com/science/article/abs/pii/S0959652621008714
International maritime Organization
http://CE Delft and UMAS, 2019
http://Corbett and Winebrake, 2018
http://Balcombe et al., 2019; Xing et al., 2020
http://Paulauskiene et al., 2019
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