[ZeroGravitas]

We produce it in immense quantity from fossil fuels and vent the fossil CO2 into the atmosphere.

The price of which is forecast to go up.

Green Ammonia is made from renewable energy, which is forecast to become cheaper.

It also requires electrolysers which are ramping up production and are also predicted to fall in price as they get made at scale from cheaper components.

So it's a fairly safe bet even if you don't believe all the published academic papers that go through the working in great detail, or the business cases that predict a multi-Billion dollar market for it.

[ClumsyPilot]

Ammonia production is already in billions of dollars, we produce 191 million tonnes

What is the basis in physics for your belief that ammonia can be produced more efficieblntly, and why was it not done already?

[ZeroGravitas]

Because it piggybacks on the political might of fossil fuel producers who are subsidized by taxpayers and don't have to pay for their externalities.

It's not "cheaper" for a mob connected waste disposal firm to dump waste into a river. If they were prosecuted for the damage they did to other people's property and had to pay for the damage they did then they'd need to raise their prices to the point that just dealing with it properly would be cheaper.

In physics terms:

Dig up hydrogen connected to carbon. Separate the hydrogen from the carbon. Release the fossil carbon into the atmosphere as CO2. Capture the same amount of CO2 from the atmosphere. Seperate it from oxygen, store the carbon. Use hydrogen to make Ammonia.

Versus

Use electricity to split water into hydrogen and oxygen. Use hydrogen to make Ammonia.

[ClumsyPilot]

So whats the best case possible efficiency?

[Sinidir]

https://www.sciencedirect.com/science/article/pii/S187661021...

This is a nice paper on the different fuel cycles of hydrogen ammonia and methyl.

Roundtrip efficiencies for hydrogen and ammonia are both at about 30% plus. Don't know how high it could theoretically go.