[kmm]

Ammonia has a negative enthalpy of formation of about -46 kJ/mol [0]. If you read the wikipedia page of the Haber process [1] it explicitly states the reaction is exothermic.

The reason the Haber process is so costly is because it uses very high pressures and temperatures to overcome the activation energy, even with the best catalysts we have. Not because creating ammonia from nitrogen and hydrogen needs energy. It's in effect wasted energy.

Enzymes can't change the cost equation, but luckily it's in our favor. If they can reduce the activation energy without wasting a ton of energy, it can be a net energy producer.

0: https://en.wikipedia.org/wiki/Ammonia 1: https://en.wikipedia.org/wiki/Haber_process

[rasmusei]

Yes, it can be a net energy producer given a source of hydrogen, but hydrogen is typically not available for free. See my other comment.

[kmm]

Nobody is saying hydrogen is free. Nor will the production of ammonia from compounds we have in abundance (i.e. water, air and rock) ever produce energy, as it's a high energy compound, releasing quite a bit of energy when combusted. But that is absolutely not what this is about.

However, I was refuting the GP's wrong assertion that the energy cost equation of this reaction shows that it cannot be a net energy producer.

It makes sense to optimize this step, because the energy equation shows the energy is just wasted as heat, as it's not contained in the compound itself.

[rasmusei]

I agree 100%. Thanks for the clarification!