Solutions for zero-emission shipping

Selma Brynolf,
Researcher,
Department of Mechanics and Maritime Sciences, Chalmers University of Technology,
Sweden

There are several initiatives and a growing momentum in the transition towards fossil free shipping at the moment. Policy and regulations are key to make the transition faster and possible for all the involved actors. Discussions are ongoing at many different levels, nationally, the European level and globally by the International Maritime Organization (IMO).

LNG was introduced as an alternative fuel as a response to the sulphur and nitrogen oxides regulations introduced by IMO in certain emission control areas (a limit of 0,5% sulphur in the fuel now also applies globally) in the 2000s and are now an established fuel. While LNG can reduce particles, nitrous oxides, and sulphur dioxide – it is still a fossil fuel and have a very limited possibility to reduce the climate change impact from shipping. Thus, there is need for other types of alternative fuels – produced from renewable primary energy sources such as solar and wind energy and biomass. It is possible to produce several different types of energy carriers from renewable energy sources including electricity, hydrogen, ammonia, methanol and methane. When produced from electricity, water and carbon or nitrogen they are typically called electrofuels, while fuels produced from biomass are typically called biofuels – both production pathways may complement each other.

In combination with renewable fuels there is a need for new ship technology, and there are several initiatives coming from the Nordic countries with examples including Stena’s conversion of a RoPax ferry to run on methanol, Maersk’s order of 8 large ocean-going vessels to operate on carbon neutral methanol, Nordled’s hydrogen-powered ferry, DFDS’s concept ferry using hydrogen and electricity, ForSea’s battery-electric ship to name a few. There is also development of ammonia engines and fuels cells.

For existing ships, renewable fuels that can be used without any extensive retrofit will be needed. Ships running on LNG can shift to renewable liquefied methane, ships running on diesel can shift to hydrotreated vegetable oil or be retrofitted to run on renewable methanol. For newbuilding’s several technology pathways are possible and the choice may be dependent on what type of ship segment and operational pattern. For short sea shipping and costal shipping, we see an increase in battery-electric ships. Battery-electric ships are already cost-efficient for some ships in these segments. For ships carrying energy carriers as cargo, there is a trend toward using the cargo as fuel – for instance for methanol, ammonia, and liquefied petroleum tankers. Previously, this was mainly the case for liquefied natural gas (LNG) carriers.

Another decisive factor is how regulations will be formed. There is a strong push towards zero-emission ships sometimes without considering the life cycle perspective. A regulation that limits emissions from the ship will push for carbon free energy carriers such as electricity, hydrogen and ammonia and disqualify carbon-based energy carriers such as methane and methanol. From an environmental and also wider sustainability perspective it is not known which types of energy carriers that will be beneficial in the long run.

Direct electrification is with present technology not possible for long distance shipping. That leaves hydrogen and ammonia, neither of these technologies are mature and even if they are promising, we do not know their performance compared to other renewable fuels such as methanol and methane. Furthermore, there is a risk of introducing a shift of environmental burden from the ship to the fuel and/or ship production if only ship emissions are regulated.

Another option is to consider the entire fuel and ship life cycle and regulate the life cycle performance. Close to zero-emission ships from a life cycle perspective could enable a smooth transition towards fossil free fuels and avoid dead ends.

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