Ammonia production is more-or-less a synonym for "hydrogen production" chemically. The NH3 formation happens at a high temperature and pressure, but it doesn't use a lot of energy. Technically, it's even energetically favorable, but with the enthalpy of just -46kJ/mol. For comparison, water is -300 kJ/mol.

In other words, to split 1 mole (18 grams) of water into constituent parts (molecular hydrogen and oxygen), you need to invest at least 300 kJ of energy. If you then use 1 mole of hydrogen to produce ammonia, you can get back 30 kJ of energy.

This is chemically pretty much the best case from the thermodynamic efficiency standpoint (especially when you also factor in the entropy changes) with almost zero potential waste.

The kicker is, of course, that you need extremely high temperature and pressure for the reaction to work. And this is just hard to do on small scale. But that's not a theoretical barrier, but "just" a question of clever engineering! It's great to hear that we're solving these issues.