Can Green Ammonia Be a Climate Fix?

[Algr]

TL;DR Summary

Alternative to current carbon-heavy ammonia production, and use of ammonia as fuel.

Wired has a new article that seems interesting.
https://www.wired.com/story/can-green-ammonia-be-a-climate-fix/

The part about eliminating the use of methane in ammonia production sounds good to me. This could also be a good case of switchable demand - if the wind or solar power dips, the ammonia plants would stop first, thus stabilizing the grid for other uses.

Then it goes into using ammonia as an alternative for methane and other fuels. That part I'm not so sure about, since using ammonia in an ICE, or otherwise using it to make electricity sounds complex. Wouldn't it make more sense to make "Green Methane" using water and CO2 from the air? Or is the process of making green ammonia that much more efficient?

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BTW: I found an old thread about ammonia here, and it got derailed with an issue where having two markets for a product was somehow equivalent to "selling it twice". I hope that has been resolved.

 

[Ygggdrasil]

I'll repeat my post from the previous thread here:

A lot of the issues with the potential for a future "hydrogen economy" that was touted in the early 2000s applies to the idea of these ammonia fuel cells. See https://www.technologyreview.com/s/402584/hype-about-hydrogen/ for a nice discussion about some of the issues with the idea of a hydrogen economy. A few additional thoughts:

1. Ammonia is not a primary energy source. The article discusses using solar energy to produce ammonia. So, the question is, is ammonia generation the most efficient use of that solar energy? In the US and many other countries, one would have greater environmental and health benefits from using solar energy to displace coal-fired power plants, than say, to generate ammonia to displace gasoline in vehicles.

2. Intermittency is a major issue with renewable energy sources like wind and solar, so storing excess energy as ammonia during off peak hours so that it can be burned later could have benefits. However, there are many other ideas and technologies for storage, and it's not clear how ammonia-based technologies would compare. It's certainly worth continuing research into the technology, but it is by no means clear that the technology will beat out some of the alternatives.

3. Similarly, it's not clear that ammonia-power vehicles would be superior to electric vehicles. Given the existing infrastructure for delivering electricity, there would have to be significant benefits from ammonia fueled vehicles to beat out EV technology. EV technology would likely be more efficient than ammonia fuels as well since you skip the step of converting electricity to ammonia and then to hydrogen as proposed in the Science News piece.

The technology does seem to provide a nice alternative to the Haber-Bosch process in a carbon-free future, however.

 

[Melbourne Guy]

So, the question is, is ammonia generation the most efficient use of that solar energy?

I've seen assumptions that curtailed RE will be used to generate green hydrogen and other products such as green ammonia, but your point and observation in your Point #2, @Ygggdrasil, is the key to this topic. It is hard to fathom large scale electrolysis from RE being cost-effective when a key manufacturing input is unpredictable. This suggests that ammonia producers will buy long-term supply contracts, just as aluminium smelters etc. do, but whether they can afford to buy the RE is questionable when higher-margin consumers will be able to pay more. Certainly, some amount of green hydrogen and green ammonia is required for industrial processes, but the huge volumes touted in the OP's article seem unlikely.

Similarly, it's not clear that ammonia-power vehicles would be superior to electric vehicles

Apart from ships, which is mentioned in the article, batteries do seem superior for most road transport compared to ammonia, especially if internal combustion engines are assumed. ICE is being driven out of urban areas because of noise, as well as CO2 and NOx.

Also, the article has a time frame to 2050. Battery energy density will increase considerably over that period and if anyone can design a workable metal-air architecture, any form of ICE or FCEV seems unlikely to compete on an efficiency basis. I remain sceptical of that. It seems a truly hard engineering problem. NantEnergy sold Zinc-air batteries but I believe it has gone out of business, Phinergy’s aluminum-air has been 'coming' for years but has not delivered, and Volkswagen's work on a lithium-air battery mooted almost a decade ago has failed to eventuate.

The technology does seem to provide a nice alternative to the Haber-Bosch process in a carbon-free future, however.

Absolutely And that's where it is likely to remain!