I’m partial to sticking them to carbon atoms for storage (methane).

How would this compare?

artemonster 3 days ago | parent | next [-]

Lets go further and synthesize them to even longer and more complex carbohydrates so that they will be liquid at normal temperature and smell nice!

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troymc 3 days ago | parent [-]

Essential oils from plants (terpenes/terpenoids) are hydrogen-rich hydrocarbons and they smell nice. Menthol is an example, with a hydrogen mass fraction of about 12%. For comparison, water has a hydrogen mass fraction of about 11.2%.

If you abandon the "smell nice" constraint, you can get an even higher hydrogen mass fraction. For example, n-pentane has a hydrogen mass fraction of about 16.8% and it's liquid at a pressure of 1 atmosphere and a temperature of 25 degrees Celsius, but it evaporates rapidly, so you need to keep it in a container.

If you don't mind pressurizing the container a bit, you could put ammonia in there, and it has a hydrogen mass fraction of about 17.6%.

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bilsbie 3 days ago | parent | next [-]

I didn’t realize the mass fractions were that low. Is that correct??

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philipkglass 3 days ago | parent [-]

Yes, because hydrogen atoms are so light. It takes 12 hydrogen atoms to equal the mass of a carbon atom and 16 hydrogen atoms to equal the mass of an oxygen atom.

	▲	bilsbie 3 days ago \| parent [-]
		It’s a surprisingly good rocket fuel to be mostly carbon then.

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artemonster 3 days ago | parent | prev [-]

It was a joke about gasoline

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ricardobeat 3 days ago | parent [-]

Smells nice?

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SoftTalker 3 days ago | parent [-]

Some people actually think it does. Especially before it had so much ethanol added. I don't think it smells particularly nice but it is definitely a memory trigger of being a small kid helping my dad get the lawn mower ready to cut the grass.

	▲	toast0 3 days ago \| parent [-]
		Ethanol free gas definitely has a more enjoyable smell than gas with ethanol, but nice is maybe the wrong word.

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ViewTrick1002 3 days ago | parent | prev [-]

Carbon is annoying (expensive) to collect from the atmosphere.

To work with a circular system you would need carbon collection on all combustion engines. Try fitting one on a plane.

And now we’re down the path of fossil industry talking points where they will ”soon” implement carbon capture and storage.

Another option is ammonia. The maritime industry is particularly interested in that one due to hydrogen taking up too much space if you want to go across oceans.

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loeg 3 days ago | parent | next [-]

> To work with a circular system you would need carbon collection on all combustion engines. Try fitting one on a plane.

Why would you need the carbon collection on planes? Surely a ground station would be equivalent and more sensible.

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ViewTrick1002 3 days ago | parent [-]

See this comment:

https://news.ycombinator.com/item?id=45313923

Direct air capture introduces processing massive volumes which causes extra energy usage.

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loeg 3 days ago | parent [-]

But like, so what? We have a lot more volume, load-bearing, and energy on the ground.

	▲	ViewTrick1002 3 days ago \| parent [-]
		Okay. Planes was a bit tongue in cheek from me. The central point was that syngas, as it stands today, only really works if you have a concentrated carbon source due to the infeasibility of direct air carbon capture. Meaning, for aviation to be freely able to release its previously captured carbon to the atmosphere we need a source for it. Capturing the exhaust fumes from a coal plant is just fossil emissions with extra steps. One source could be biofuels and biogas from waste. But is that enough to run all airtravel on? Likely not. And if the carbon source is biofuels then we might as well just skip making syngas and run the airplanes on it directly. The aviation industry have enormous problems to solve, and for it to work I think direct air capture needs to be solved. Or they need to manage with liquid hydrogen or ammonia. Come to think of it; ammonia and an airplane crash sounds like a terrible recipe... For maritime shipping they alreay have engines running on hydrogen, methanol, syngas, syndiesel, ammonia and whatever else that is liquid at any temperature and makes a bang. They also have the space to install carbon capture systems if they choose to go down carbon based fuels allowing them to not be reliant on direct air capture. This is why they truly like ammonia. It is a liquid with similar nastiness properties as methanol which they know how to deal with. Nitrogen is trivial to capture and it makes a bang when ran in an engine.

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AnotherGoodName 3 days ago | parent | prev | next [-]

Fwiw it's pretty trivial to make synthetic methane and has similar overall efficiency to making hydrogen from electricity. We have no more trouble collecting carbon atoms than we do hydrogen atoms.

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chii 3 days ago | parent | prev | next [-]

> need carbon collection on all combustion engine

why not simply centralize the carbon collection and synthesis in some area (preferably where the sun shines a lot), then pipe/transport the resulting hydrocarbon fuel to where it is needed?

	▲	crote 3 days ago \| parent [-]
		Because centralized carbon collection isn't simple. About 0.0427% of the atmosphere is CO2, getting rid of the other 99.9573% you don't want to capture is rather tricky*. The most efficient way is probably by using plants - but that doesn't really scale. On the other hand, the output of a methane-powered fuel cell is 33% CO2 and 66% H2O - with the water being rather trivial to filter out. Even a dirty regular combustion engine outputs about 14% CO2.

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bilsbie 3 days ago | parent | prev [-]

Check out terraform industries for some ground breaking concepts and prototypes on this.