To reduce the climate impact of shipping, the introduction of alternative fuels is required. There is a range of different marine fuel options but ammonia, a potential zero carbon fuel, has recently received a lot of attention. The purpose of this paper is to assess the prospects for ammonia as a future fuel for the shipping sector in relation to other marine fuels. The assessment is based on a synthesis of knowledge in combination with: (i) energy systems modeling including the cost-effectiveness of ammonia as marine fuel in relation to other fuels for reaching global climate targets; and (ii) a multi-criteria decision analysis (MCDA) approach ranking marine fuel options while considering estimated fuel performance and the importance of criteria based on maritime stakeholder preferences. In the long-term and to reach global GHG reduction, the energy systems modeled indicate that the use of hydrogen represents a more cost-effective marine fuel option than ammonia. However, in the MCDA covering more aspects, we find that ammonia may be almost as interesting for shipping related stakeholders as hydrogen and various biomass-based fuels. Ammonia may to some extent be an interesting future marine fuel option, but many issues remain to be solved before large-scale introduction.
The transport sector is often seen
as the most difficult sector
to decarbonize. In recent years, so-called electrofuels have been
proposed as one option for reducing emissions. Electrofuelshere
defined as fuels made from electricity, water, and carbon dioxidecan
potentially help manage variations in electricity production, reduce
the need for biofuels in the transportation sector while utilizing
current infrastructure, and be of use in sectors where fuel switching
is difficult, such as shipping. We investigate the cost-effectiveness
of electrofuels from an energy system perspective under a climate
mitigation constraint (either 450 or 550 ppm of CO2 in
2100), and we find the following: (i) Electrofuels are unlikely to
become cost-effective unless options for storing carbon are very limited;
in the most favorable case modeledan energy system without
carbon storage and with the more stringent constraint on carbon dioxide
emissionsthey provide approximately 30 EJ globally in 2070
or approximately 15% of the energy demand from transport. (ii) The
cost of the electrolyzer and increased availability of variable renewables
appear not to be key factors in whether electrofuels enter the transport
system, in contrast to findings in previous studies.
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