Future path for shipping fraught with peril?
Jukka-Pekka Jalkanen,
Senior Researcher,
Finnish Meteorological Institute,
Finland
Shipping will be irrevocably changed in the future and the driver will be environmental pressures. The detrimental impacts of air pollutants, NOx, SOx and Particulate Matter (PM) have led to regulatory changes at all levels, from local to global. In the Baltic Sea region (BSR), reductions of Nitrogen and Sulphur have been agreed at the International Maritime Organization (IMO), but the compliance options were left for ship owners to choose. Some of these may lead to unexpected side effects.
The global switch to low Sulphur fuel in 2020 was easier than expected, probably because lot of experience had been gained. Low Sulphur fuel could be a costly option if the annual fuel consumption and the price difference between low- and high Sulphur fuels is high.
Alternative option is the use of Sulphur abatement techniques (affects also PM and Black Carbon (BC)) from ship exhaust. In its simplest form, open loop scrubbers, seawater spraying cleans the exhaust gas and the effluent is released back to the sea. Other scrubber options also exist, but these are more expensive than the open loop system. Air pollution is decreased but the effluent creates a new water pollution stream, the impacts of which are not known well. The risk of open loop scrubbers creating a new problem lies on those who have chosen to adopt this path. Most of the scrubbers in the global fleet are of open loop type, which means that this is a global issue in areas with low water volume or limited water exchange.
The use of scrubbers has increased sharply, first in the Baltic Sea area but also globally since the introduction of global Sulphur cap in 2020. There were 95 scrubber ships in the BSR in 2019 and the effluent release of the fleet was the second largest release (by volume) of water pollution from ships after the ballast water discharge. The release of heavy metals, polyaromatic hydrocarbons and other components from ships to the sea has led to local bans of open loop scrubbing in some port areas or close to the shoreline, even if limit values for scrubbers have not been exceeded. The precautionary principle prohibits releasing anything potentially harmful to the sea.
These options are not enough when other air pollutants are considered. From 2021 onwards, also 80% NOx reduction is required from new ships in the BSR. This will gradually reduce the NOx emissions, but its full effect will only be seen once the fleet has gone through one renewal cycle, which can take 25-30 years.
Since the two options mentioned above can be used to cope with SOx regulation but not NOx, it is tempting to switch to gaseous fuel like LNG (liquid natural gas), which is basically methane, and solve both problems simultaneously. LNG engines emit very little Sulphur or particles, which means that BC or scrubber effluent problems are avoided. Depending on the type of LNG engine, it may offer also significant NOx reduction. It can increase the emissions of unburnt methane to the atmosphere, known as methane slip. There are three types of LNG engines, two of which have low NOx emissions but high methane slip and one type with high NOx emissions and low methane slip. With a correct choice of engine, both SOx and NOx requirements can be met with a gas engine.
This brings us to the problem of LNG. First, methane regulation is very likely since methane is a strong greenhouse gas and this increasing emissions source cannot be overlooked by the IMO. Second problem arises from the fact that LNG of today is a fossil fuel and its burning increases CO2 in the atmosphere. Considering the investments made to gas pipelines, terminals, storages and shipping fleet, it would be logical to make best use of existing infrastructure as far as possible. Methane can be produced synthetically, which involves breaking H2O molecule to hydrogen and oxygen with electricity and combining the hydrogen with carbon taken from CO2. Similar processes are involved in manufacturing of methanol and ammonia, which are considered as potential future fuels for ships.
These three fuels have significant benefits. They can be used in internal combustion engines (ICE) and fuel cells, which are considered as a future of shipping. This provides an opportunity to shift the fossil-powered fleet towards greener fuels. All three fuels are hydrogen carriers and have intermediate hydrogen step in their production process. If the electricity needed by this process is taken from wind or the sun, then the need to use fossil energy is removed. All three fuels can be mixed with their fossil counterparts and this can be used to gradually increase the share of non-fossil fuel. It could be said that these fuels buy time for ICEs when moving towards ships operated with fuel cells.
The next 10-20 years will be critical. One significant challenge is to ensure that the shift from fossil to synthetic fuels really occurs. We cannot afford to get stuck with fossil fuels and lose the flexibility ICEs provide in decarbonizing shipping.
Expert article 2883
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