Comment by photochemsyn | Hacker News Reader

Comment by photochemsyn | Hacker News Reader

This article seems rather confused at best. Take this:

> "So-called clean ammonia comes in two main varieties: green, produced with hydrogen that is created by splitting water with renewable electricity; and blue, made with traditional hydrogen from which the by-product CO2 is captured and stored underground."

Underground storage of carbon dioxide from fossil fuel combustion has been over-hyped for decades and never convincingly demonstrated. It still appears that the energy cost of collecting, piping and injecting all the CO2 from a fossil fuel combustion or hydrogen reformation process exceeds the total amoung of energy that the process generates. That means all the power produced by the fossil fuel power plant would be devoted to capturing, transporting and injecting the resulting carbon dioxide - a futile cycle leaving no energy available for any other use.

Additionally, you have to ensure that the combustion of ammonia generates N2, not NOx (nasty air pollutants). The article doesn't seem to mention it, but it is an issue, for example:

https://nh3fuelassociation.org/2017/10/01/methods-for-low-no...

I worked on the Front End Engineering Design for a blue hydrogen power station with carbon capture, and I can assure you it generated net electricity export after subtracting the power and heat requirements for the CO2 compression and amine units respectively. So the phrase "It still appears that the energy cost of collecting, piping and injecting all the CO2 from a fossil fuel combustion or hydrogen reformation process exceeds the total amoung of energy that the process generates" is definitely not true. And contrary to common opinion, there is no "unproven technology" in CO2 capture and storage, every unit operation has been around for decades.

However your other phrase was 100% correct I think: "Underground storage of carbon dioxide from fossil fuel combustion has been over-hyped for decades and never convincingly demonstrated." I'm not 100% sure why that is, but I think it is probably to do with the lack of economic incentive combined with relatively little industry experience. If every Operator knew without a shadow of a doubt their Scope 3 emissions would get taxed at $100US per tonne CO2 then a whole industry would spring up and CO2 capture would become commonplace. But you don't get there with a smattering of plants across the world, with various incentives.

A few years ago I tried to dive into the question of whether DOE-financed projects like FutureGen and other fossil-carbon-capture-and-sequestration efforts had any solid scientific basis, and I always ran up a against a brick wall of proprietary data in these 'public-private partnerships', when it came to figuring out the ratio of carbon going into the plant in the form of gas/oil/coal, and carbon coming out of the plant in the form of CO2, and the fraction of that CO2 that was actually being stored vs. the fraction being emitted to the atmosphere.

My conclusion such as it was (not having full data access) was that all these plants only captured a relatively small fraction of their CO2 emissions, and more often than not, were simply using that CO2 in enhanced oilfield recovery operations - and here again, it seemed that a good fraction of the injected CO2 was coming back out of the ground with the oil it was intended to extract, then being boiled off [to the atmosphere] in the distillation process.

All in all I think it's probable that a complete external investigation of this ~20 year saga of public-private 'carbon capture and sequestration' programs at the US DOE would not look good at all, and might reveal a fair amount of blatant fraud.

[one can sort of grasp the problem by imagining if a gasoline-powered vehicle driving down the road would ever be capable of capturing its CO2 emissions in some onboard storage tank, which could then be offloaded at a gas station when refueling for 'permanent underground storage'.]

On your project, what ratio of generated energy was spent on CO2 capture and storage?

The greenhouse gas emissions of blue hydrogen production exceed those of simply burning natural gas.

https://onlinelibrary.wiley.com/doi/full/10.1002/ese3.956

I think the real meat of the article is further down, where they discuss replacing the Haber-Bosch process. That's what the article really ought to be about. Haber-Bosch is a huge emitter of CO2, and our industrial agriculture depends on it. That they intend to replace methane with ammonia would be nice, but regardless of that, if this Tsubame process can be made to work, it will have applications beyond that.

They also talk about ammonia replacing methane in power plants, which is problematic.

It’s very difficult to combust ammonia without producing a lot of NOx. That means more smog, acid rain, asthma and other respiratory disorders.

We’ve gone to huge efforts to reduce and eliminate NOx emissions from vehicles and power plants, so it would be a major setback to start adding new sources of it.

Wouldn’t industrial processes that use H2 directly generally be preferable to having ammonia as an intermediary?

NOx are industrially useful and profitable to scrub out at large scale (and relatively easy too, just pass exhaust gasses through water) because it generates nitric acid, which is an extremely useful and relatively expensive chemical that is the basis for vast amounts of industrial processes. So the use of ammonia in power plants is relatively unproblematic, in fact I would not be surprised if tuning ammonia based power plants to produce the most amount of NOx possible was the most economic choice.

As a bonus, nitric acid can be directly used to create fertilizers, which is one of the central usages of the Haber–Bosch process.

Not sure, whether there's a technically proven ammonia fuel cell yet. For some applications it could enable the use ammonia to generate electricity _without_ NOx emissions.

There is. It is practical to operate at a scale as small as a single wind turbine, for local fuel and fertilizer on a farm.

Where and how do you recommend learning more about this? Thanks.

You minimize NOx production just by running a little bit rich.

NOx output from natural gas plants is today kept down by injecting ammonia.

Haber-Bosch itself does not emit CO2. I presume you mean that the generation of H2 needed for Haber-Bosch is what emits the CO2 - unless using green hydrogen?

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