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Low carbon innovations for maritime freight

“Hydrogen from renewable sources is key to carbon-free maritime transport”

Anaïs Marechal, science journalist
On May 4th, 2022 |
3 min reading time
Delphine Gozillon
Delphine Gozillon
Sustainable Shipping Officer at the European Federation for Transport & Environment
Key takeaways
  • The energy transition to liquefied natural gas (LNG) is not so good as it remains a fossil fuel that releases methane when used. About 3% of the 80% used by ships.
  • The use of biofuels is not particularly adapted to the shipping sector. Many sectors, notably aviation, will need 2nd and 3rd generation biofuels to achieve decarbonisation.
  • Two thirds of current GHG emissions could be avoided with a renewable energy mix and hydrogen seems to be the best alternative to fossil fuels.
  • The main limitation, behind the cost of these e-fuels, is the deployment of the whole sector. The challenge is to produce enough renewable hydrogen.

Between 2012 and 2018, the International Maritime Organisation1 noted a significant shift in the energy mix of carriers towards liquefied natural gas (LNG) and methanol. What are your thoughts on that?

Today the sector’s ener­gy mix is still 99% fos­sil fuel based. It is dif­fi­cult to mea­sure a trend in green­house gas (GHG) emis­sions because of the dis­rup­tion caused by the Covid-19 cri­sis. Nev­er­the­less, a tran­si­tion to LNG is observed, we esti­mate in 2020 that it rep­re­sents 6% of the fuel used for Euro­pean mar­itime trans­port, and that this share could rise to almost 25% by 2030. The tran­si­tion is neg­a­tive for two rea­sons. First, it is a fos­sil fuel. Sec­ond, 80% of LNG is cur­rent­ly con­sumed by ships whose engines release about 3% of methane – a pow­er­ful GHG – into the atmos­phere. The car­bon foot­print is there­fore high­er over the life cycle than con­ven­tion­al fuels 2.

Some large shipown­ers such as Maer­sk are mov­ing towards methanol. Most methanol is cur­rent­ly pro­duced from fos­sil resources. How­ev­er, it is pos­si­ble to syn­the­sise it from renew­able hydro­gen… It is nec­es­sary to impose reg­u­la­to­ry con­straints on the ori­gin of fuels. This is cur­rent­ly being dis­cussed at Euro­pean lev­el, by the Mem­ber States and the Euro­pean Parliament.

Does the renewable origin of a fuel always make it virtuous?

We must pay atten­tion to this fac­tor, but also to con­flicts of use. For exam­ple, the pro­duc­tion of bio­fu­els must not com­pete with food pro­duc­tion or lead to changes in land use. Only bio­fu­els pro­duced from waste are vir­tu­ous. The avail­abil­i­ty of the resource is anoth­er very impor­tant con­sid­er­a­tion. Many sec­tors, notably avi­a­tion, will need 2nd and 3rd gen­er­a­tion bio­fu­els to low­er car­bon foot­print. We have esti­mat­ed that the trans­for­ma­tion of all agri­cul­tur­al residues would only cov­er a lit­tle more than 10% of aviation’s needs in 2050. We do not believe that the use of bio­fu­els is rel­e­vant for the ship­ping sector.

What is the ideal fuel to decarbonise shipping?

Two thirds of cur­rent GHG emis­sions could be avoid­ed with a renew­able ener­gy mix3. Avail­abil­i­ty for large-scale deploy­ment must also be con­sid­ered. For small riv­er ves­sels, elec­tric propul­sion is inter­est­ing and already used. How­ev­er, the capac­i­ty of the bat­ter­ies does not allow to pow­er large ves­sels today. For them, hydro­gen-based fuels of renew­able ori­gin are the most suitable.

For short to medi­um dis­tances, hydro­gen can be used direct­ly in a fuel cell or com­bus­tion engine. For long dis­tances, the space need­ed to store large quan­ti­ties of hydro­gen is a lim­i­ta­tion. Elec­tro­fu­els (see box) are the best alter­na­tive. I am think­ing, for exam­ple, of e‑methanol or e‑ammonia, pro­duced from hydro­gen of renew­able ori­gin. The poten­tial for reduc­ing GHG emis­sions using these solu­tions is esti­mat­ed at over 70%, or even 100% in the case of e‑ammonia.


E‑fuels refer to all hydro­gen-based fuels, usu­al­ly in liq­uid form for marine use. In addi­tion to hydro­gen itself, e‑fuels include e‑ammonia, made from hydro­gen and nitro­gen. Syn­thet­ic fuels, such as e‑methanol, e‑methane, and e‑diesel, are made from hydro­gen (H2) and car­bon diox­ide (CO2). Hydro­gen can be pro­duced by elec­trol­y­sis of water and then com­bined with CO2 in a ther­mo­cat­alyt­ic reac­tor to pro­duce the fuel. CO2 can be cap­tured from the atmos­phere, or from bio­log­i­cal sources such as agri­cul­tur­al and house­hold waste. Their car­bon foot­print can be much less attrac­tive if the car­bon and hydro­gen are of fos­sil ori­gin: the life-cycle car­bon foot­print then becomes greater than con­ven­tion­al fuels.

The main lim­i­ta­tion at present is their price. All renew­able hydro­gen fuels are very expen­sive. E‑ammonia, the cheap­est of them, is about 4 times more expen­sive than bio­fu­els 4. Of course, wider adop­tion will bring economies of scale. But their price will inevitably remain high­er than that of fuel oils. 

Is it already possible to use synthetic fuels in merchant ships?

The tech­nol­o­gy is mature, but it is aimed more at renew­ing the mar­itime fleet: a design and engines adapt­ed to e‑fuels are need­ed for effi­cient ship oper­a­tion. About a third of the Euro­pean fleet is at the end of its life, so the solu­tion is rel­e­vant. The first engines using ammo­nia are expect­ed to be mar­ket­ed by the Ger­man com­pa­ny MAN ES by 2024. Wärt­silä, anoth­er man­u­fac­tur­er, is also prepar­ing ammo­nia-methanol engines. Asian ship­yards have announced the first com­mis­sion­ing of ammo­nia con­tain­er ships in 2025. 

The main lim­i­ta­tion, beyond the cost of these e‑fuels, is the deploy­ment of the whole sec­tor. In Den­mark and Nor­way, projects for the pro­duc­tion and use of renew­able e‑methanol, hydro­gen and e‑ammonia are being set up: the chal­lenge remains to pro­duce enough renew­able hydro­gen. The EU’s tar­gets have just been increased due to the cri­sis in Ukraine, and now aim to pro­duce over 20 mil­lion tonnes of hydro­gen by 2030. There is also a need to devel­op the infra­struc­ture to sup­ply ships, espe­cial­ly as con­ver­sion pos­si­bil­i­ties are lim­it­ed. For exam­ple, ammo­nia is tox­ic and cor­ro­sive and requires ded­i­cat­ed stor­age facil­i­ties. This does not apply to e‑diesel, which has the advan­tage of work­ing with exist­ing ships and infra­struc­ture. But the extreme­ly high cost, much high­er than e‑ammonia, may make its large-scale use prohibitive.

Leg­is­la­tion cur­rent­ly favours the deploy­ment of LNG infra­struc­ture: we believe it is more appro­pri­ate to encour­age the deploy­ment of ded­i­cat­ed hydro­gen and ammo­nia refu­elling infra­struc­ture and to intro­duce min­i­mum tar­gets for the use of e‑fuels by ships.

1Organ­i­sa­tion mar­itime inter­na­tionale, Fourth IMO GHG Study 2020, 2021.
2Trans­port & Envi­ron­ment, 2022, FuelEU Mar­itime : T&E analy­sis and recom­man­da­tions. How to dri­ve the uptake of sus­tain­able fuels in ship­ping
3Trans­port & Envi­ron­ment, 2021, Decar­bon­is­ing Euro­pean Ship­ping. Tech­no­log­i­cal, oper­a­tional and leg­isla­tive roadmap
4T&E, based on cost assump­tions of Ricar­do EAE and UMAS-LR

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