
New ammonia production process: generates electricity instead of consuming - ph0rque
https://phys.org/news/2017-02-flipping-ammonia-production-electricity-consuming.html
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rasmusei
Replying to a number of previous comments on energy balances.

The reaction N2 + 3 H2 -> 2 NH3 is exothermic, giving off energy [1]. N2 is
abundant and free (80% of the atmosphere), but H2 is not. The most common way
[2] of producing H2 is from hydrocarbons (oil/gas products). In principle H2
can be produced from something else (e.g. water, through electrolysis), but
that is _very_ energy intensive [1], making the overall reaction N2 + 3 H2O ->
2 NH3 + 3/2 O2 a net energy consumer.

Point being, yes, it might be possible to save energy compared to the Haber-
Bosch process, but the net production of ammonia from free/abundant materials
will not ever be "for free" energy-wise.

[1]
[https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation](https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation)
[2]
[https://en.wikipedia.org/wiki/Hydrogen_production](https://en.wikipedia.org/wiki/Hydrogen_production)

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msandford
ATP is required to make the reaction happen. My suspicion is that it's energy
net-negative. Sure you make some electricity but how much does it cost to make
ATP? Probably more than you get out in electricity. Not that there's a fast
and easy way to turn electricity into ATP.
[https://www.reddit.com/r/askscience/comments/46ax8r/can_elec...](https://www.reddit.com/r/askscience/comments/46ax8r/can_electricity_be_used_to_convert_adp_to_atp_in/)

~~~
rosalinekarr
Theoretically, ATP could be harvested from plants or bacteria. They could also
be modified to produce the ammonia directly via this reaction. That wouldn't
actually reduce the energy cost, but it could reduce the economic cost by
making it logistically easier to produce. Maybe instead of making ammonia in
complicated chemical plants, we could "grow" it on farms.

~~~
msandford
I mean, sure, you can do that. But it's kind of silly. "Grow" ammonia
feedstock on farms to then turn into fertilizer to use at the farm to grow
food?

Maybe you should just plant legumes instead and let them fix the nitrogen
straight into the soil where you want to grow food. It's not sexy since it's
19th century technology (or older) but it works. And it requires very little
in the way of logistics or infrastructure meaning that it's resilient.

[https://en.wikipedia.org/wiki/Nitrogen_fixation](https://en.wikipedia.org/wiki/Nitrogen_fixation)

~~~
VLM
Oh you city slickers... This has been a thing for centuries and it works
pretty well. Getting big industry in the middle of the process would be new
but the process is old.

[https://en.wikipedia.org/wiki/Green_manure](https://en.wikipedia.org/wiki/Green_manure)

