C Alvin Scott
Hello, this is not so good, there is the case that the Nitrogen content on Ammonia when combusted joins with oxygen easier than nitrogen in Air as when kerosene is used in a gas turbine so in terms of NOx this is worse option to cut CO2
Ammonia has been used in road vehicles successfully. I believe it was used in Belgium in WW2 in trams.
It is a noxious gas, but disperses quickly. The article implies that more energy is obtained by separating hydrogen by catalysis, than by burning ammonia (NH3) directly. Is this correct?
Why waste so much time and effort, when CO2 is not a pollutant, except in the myths of the mainstream media?
Brian M
The logical way forward is to invest in trying to efficiently create a kerosene substitute that can be used in the current fleet of aircraft from a green processes that fixes as much carbon as is burnt during its use, with energy for the production process coming from renewable/non-carbon source.

nd , i.e fixing the components from th eatmosphere and usign green
I wonder if seeding the atmosphere with nitrogen oxides will affect the weather? No one seems to worry about acid rain anymore.
"Though it only has a third of the energy density of diesel"

Nobody here ever heard of a fuel called "bio-diesel"?
(Which can be easily/cheaply produced from a very wide range of bio-mass & can be also used for all trucks & ships as well as aircraft & would require almost no infrastructure/design changes?)
There is a hugely important factor missing from the analysis, so far: cost. Ammonia is already commercially available, so it shouldn't be hard to guess the base cost. But carrying three times (?) more fuel and it being pressurized means increased cost for each flight, even after paying for upgraded tanks and engines.
I would think that Bio-fuels would offer a better alternative...as a drop-in replacement for Kerosene. As I try to unpack this statement: "In this new system, the ammonia is stored as a chilled, pressurized liquid in the wings of the airplane just as kerosene-based fuel is today." I did not think modern airplanes can store chilled and pressurized fuels. To me this seems like an engineering re-design that would be no small feat...
I hope someone bothers to check the exhaust gasses for the various reactive molecules (NOx and others) and how they would react with the upper atmosphere, before bringing this to market. Remember: CFCs were the wonderful solution to the problems of their time. For that matter, fossil fuels were the answer to the problems of their time.
Expanded Viewpoint
Oh good grief, here we go again!! Ammonia, (NH3) doesn't grow in nature, it's a chemical compound that is created by people in factories. Therefore, it has a "bad Carbon footprint" attached to it. Carbon based fuels are used to generate the electricity that makes the Ammonia. Is everybody following along here? Then, you need trucks that run on Carbon based fuel to haul it hither and yon, unless you have a vast network of piping to deliver it, and again, lots and lots of carbon based fuels are involved, leaving their footprints all over the landscape.
Then, we move on to Oxides of Nitrogen, possibly, as we're not told just how any energy that is invested into the production of the Ammonia is pulled back out of it, nor at what level of efficiency. In short, it's just another boondoggle that will never "get off the ground" no matter how many pretty pictures of it are painted for us to gaze upon and marvel at.