If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.



Ammonia on route to fuel ships and planes

Carbon-neutral ammonia could be a drop-in replacement for fossil fuels

by Alex Scott
August 12, 2020 | A version of this story appeared in Volume 98, Issue 31


So-called green ammonia is made by reacting nitrogen separated from air with hydrogen made by wind- or solar-powered water electrolysis. It could be an environmentally friendly fertilizer or, backers say, a safe, low-emissions fuel for ships and planes.

A photo of a ship that could be converted to be fueled by ammonia.
Credit: Haldor Topsoe
Haldor Topsoe says ships such as this one can be adapted to run on green ammonia.

A new report by the Danish catalyst company Haldor Topsoe and partners concludes that replacing conventional fuel oil with green ammonia could be a cost-effective way of reducing greenhouse gas emissions from ships.

Green ammonia would be a cheaper fuel for the shipping industry than hydrogen made from renewable energy because it is easier to store and can be burned in standard internal combustion engines. Nitrogen oxides—the only greenhouse gases emitted by the combustion of ammonia—could be eliminated by installing catalytic systems, the Danish firm states.

Topsoe forecasts in its study that the cost of green ammonia from solar and wind energy will be $21.50–45.70 per GJ in 2025, dropping to $13.50–15.00 in 2040. Fuel oil today is priced at $12.50–15.00 per GJ. Ammonia can be mixed with fuel oil, enabling its use to be increased steadily.

Conventionally made ammonia is already stored and handled in 120 ports around the world, meaning it can easily be made available for shipping, the report concludes.

Green ammonia is also being lined up as a fuel for airplanes. The British aircraft-engine manufacturer Reaction Engines says it is working on a fuel system in which ammonia is exposed to a catalyst that splits it into nitrogen and hydrogen, with the latter burned in the aircraft engine.

Ammonia has the advantage over hydrogen in that it can be stored in an aircraft’s wing, as kerosene is today. Ammonia is, however, less energy dense than kerosene, so its use would be limited to short-haul flights.

Reaction Engines is developing the technology along with partners at the Harwell Campus science park in Oxfordshire, England. The project has secured funding from the UK’s Science and Technology Facilities Council.

Ammonia is a major global commodity, with annual production of about 230 million metric tons, according to IHS Markit. The market research firm says green ammonia could “change the landscape” for the ammonia industry over the next 10–20 years.



This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.