There are a number of e-fuels that could be synthesised from low-carbon hydrogen, but the ones widely expected to perform best in coming decades are the synthetic fuels best suited to decarbonise long-distance maritime shipping and aviation—e-ammonia and e-kerosene respectively.

Despite their additional costs, these two e-fuels also are viewed as better options than the use of straight hydrogen in these sectors. This is because of their superior energy density and the high cost of storing liquefied hydrogen on vessels and aircraft.

The first part of this two-part series explores the potential of e-ammonia for shipping through 2050 as well as the major barriers it must first overcome.

Potential scale

E-ammonia is expected to become the preferred option for shipping a decade or so earlier than e-kerosene will for aviation.

In 2018, delegates to the annual meeting of the International Maritime Organization (IMO), the UN entity that regulates the industry, agreed to reduce carbon dioxide (CO₂) emissions by 50pc from 2008 levels by 2050. Maritime shipping presently contributes almost 3pc of global total anthropogenic CO₂ emissions.

"The main constraints for the adoption of e-ammonia by the shipping industry are not technological, but political" Smith, UCL

Fortunately for the global shipping industry, e-ammonia should come to the industry’s rescue over the next three decades, as indicated by the IEA’s recently released net-zero emissions scenario. In this IEA scenario, e-ammonia accounts for 45pc of the shipping industry’s energy mix by 2050 compared with almost none currently. And according to international consultancy DNV in a report released in September 2019, nearly all newly built ships should be running on e-ammonia from 2044 onwards.

“The main constraints for the adoption of e-ammonia by the shipping industry are not technological, but political,” Tristan Smith, a professor at University College London’s Energy Institute, tells Hydrogen Economist.

“If the IMO was to progressively ban the use of fossil fuels by vessels or incentivise the use of the hydrogen-derived fuel through some form of carbon pricing, we could possibly get even higher than the IEA’s 45pc figure by 2050.”

Major technical barriers

The cost of producing e-ammonia is presently about twice the price of very low-sulphur fuel oil. The two major drivers for the cost discrepancy are relatively high prices for green electricity and capex outlays, both of which are likely to decline in the future, according to Hendrik Brinks, principal researcher for non-carbon fuels at DNV.

“There are significant but not insurmountable technical and safety challenges associated with ammonia as a marine fuel,” Brinks tells Hydrogen Economist. “Due to the high toxicity and corrosiveness of ammonia appropriate safety barriers need to be in place, material selection is of paramount importance. In addition, commercial two-stroke engines fuelled by ammonia are presently under development, and likely three or four years away.”

3pc – Global emissions produced by maritime sector

Brinks and Smith both believe ocean-crossing ships powered by e-ammonia should be commercially available by 2025, with quite a few related projects already underway. These include:

• Finland’s Wartsila’s plans to test ammonia in a modified marine diesel engine in Stord, Norway.

• Korean shipbuilder Samsung Heavy Industries and Germany’s MAN Energy Solutions developing an ammonia-fuelled oil tanker as part of a larger consortium with a 2024 target launch date. 

• Viking Energy, an offshore supply vessel chartered by Norway’s Equinor, which aims to become the first vessel propelled by ammonia fuel cells, also in 2024.

The timeline for e-ammonia fuel cell-powered ships for long distance routes is much longer as their power requirements are far greater.

The second part of the series looks at e-kerosene and how effectively it may be able to decarbonise the aviation sector, which, like the maritime sector, does not fall under any nations' contributions to the Paris Agreement.

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Author: Vincent Lauerman