Carbon-neutral petrol

[OwlHoot]

In climate change discussions it is axiomatic that use of fossil fuels is evil, which is fair enough. But then imperceptably that morphs into "hydrocarbons are evil", and ICE vehicles must all be swept away to leave only electric, and anyone who ventures to suggest otherwise either works for an oil company or is a bit loopy!

Fossil fuels are bad only because their combustion releases long-sequestered CO2 all at once. But what if petrol or diesel could be produced from CO2 already in the atmosphere, by some process using suitable catalysts and another energy source such as solar or nuclear? The fuel would be carbon neutral then, even when combusted. In principle, "hydrocarbon" need not be synonymous with fossil", even though it has been so until now.

Not being an industrial chemist, I don't know if hydrocarbon production "from scratch" like that could ever be made efficient enough to be practical. But if so then it would have some advantages, and we could go on using petrol and the like as handy high-density fuels as they are now, with engines whose efficiency has been honed for over a century with further improvements possible.

Another advantage is that it would avoid soon having to manufacture literally billions of electric batteries for vehicles, and keep reconditioning these and having to manufacture more, as this will cause massive pollution in itself, not to mention likely resourcing issues and squabbles for all the weird and wonderful rare earth elements required in them:

2021-11-04 The Dirty Truth About Clean Technologies

So I wouldn't be surprised if in 100 years there are large flotillas of oil tankers out in the Atlantic, with their decks covered in solar panels or surrounded by floating solar sheets, and busily churning out petrol, and ICE cars are still going strong!

[malvolio]

Well the first problem is getting the CO2 separated into C and O2

Oh,hang on, you need a tree....

Otherwise it's a very strong bond that requires energy to break.

[jayn200]

Where are you going to capture emissions? This likely won't solve localized air pollution problems which no one talks about anymore but cause way more deaths than climate change.

[OwlHoot]

Well the first problem is getting the CO2 separated into C and O2

Oh,hang on, you need a tree....

Otherwise it's a very strong bond that requires energy to break.

Of course. I wasn't suggesting you could produce hydrocarbons without requiring a fair bit of energy and suitable catalysts, speaking of which:

2017-06-05 Splitting carbon dioxide using low-cost catalyst materials

A promising avenue for the future of clean energy is to store it in the form of carbon-based fuels produced from renewable sources, effectively enabling the clean use of liquid fuels such as gasoline. A first step is the electrolysis of carbon dioxide into oxygen and carbon monoxide. But current CO-forming catalysts are either not selective enough or too expensive to be industrially viable. Now scientists have developed an Earth-abundant catalyst based on copper-oxide nanowires modified with tin oxide.

[Lance]

It’s fiendishly difficult (energy intensive) to make hydrocarbons from the air.

you need to step back even further though. Why are hydro carbons useful?
1. Availability. Just drag it out if the ground.
2. distribution already in place.
3. long term storage is easy.

if you were to use another liquid chemical then 2&3 are covered. Alcohol does this already. And is far more efficient. You just need a source of sugar/carbohydrate and yeast.

[malvolio]

It’s fiendishly difficult (energy intensive) to make hydrocarbons from the air.

you need to step back even further though. Why are hydro carbons useful?
1. Availability. Just drag it out if the ground.
2. distribution already in place.
3. long term storage is easy.

if you were to use another liquid chemical then 2&3 are covered. Alcohol does this already. And is far more efficient. You just need a source of sugar/carbohydrate and yeast.

Doesn't matter where it comes from, if energy is dependent on combustion then you are back to square one. Hydrogen is the way forward, via fuel cell technology and is fairly simple to obtain (off peak electrolysis of water is hardly rocket science, you could do it at home ), it's the storage and distribution architecture that is the tricky bit. Then again I can fill my motorhome with pressurised LPG (barely less dangerous than liquid H2) at a conventional pump, so it's clearly possible. As California are proving.

[OwlHoot]

Doesn't matter where it comes from, if energy is dependent on combustion then you are back to square one.

Sure, Again I wasn't claiming that combusting manufactured hydrocarbons would reduce the amount of CO2 in circulation just not add to it, hence the phrase carbon-neutral.

Hydrogen is the way forward, via fuel cell technology and is fairly simple to obtain (off peak electrolysis of water is hardly rocket science, you could do it at home ), it's the storage and distribution architecture that is the tricky bit. Then again I can fill my motorhome with pressurised LPG (barely less dangerous than liquid H2) at a conventional pump, so it's clearly possible. As California are proving.

I did read somewhere that hydrogen leaks terribly over time, so long-term storage is a big problem. But then if Count von Zeppelin could do a fair job of storing it over 100 years ago, they've probably ironed out the wrinkles by now.

Also, I take Lance's point about alcohol as an ICE fuel. But you'd have to adulterate it with some noxious combustion-neutral unextractable additive, to prevent idiots drinking it!

[tazdevil]

Doesn't matter where it comes from, if energy is dependent on combustion then you are back to square one. Hydrogen is the way forward, via fuel cell technology and is fairly simple to obtain (off peak electrolysis of water is hardly rocket science, you could do it at home ), it's the storage and distribution architecture that is the tricky bit. Then again I can fill my motorhome with pressurised LPG (barely less dangerous than liquid H2) at a conventional pump, so it's clearly possible. As California are proving.

Hydrogen is the way forward but as a combustion engine fuel rather than using expensive and fragile fuel cells to convert hydrogen to electricity

[vetran]

Hydrogen is the way forward but as a combustion engine fuel rather than using expensive and fragile fuel cells to convert hydrogen to electricity

initially with adapted engines, then as they develop via fuel cells. walk before you can run..

I agree Hydrogen is an easy drop in replacement.

[malvolio]

initially with adapted engines, then as they develop via fuel cells. walk before you can run..

I agree Hydrogen is an easy drop in replacement.

Not that easy. You can't put pressurised liquid hydrogen into an unmodified fuel system, plus you need a specialised regulator, but none of that is all that difficult to overcome. It's not as energy dense of petrol (very little is, actually) so you'll use a lot more by volume, but the end result is comparable.

I've seen someone claim it will produce NOx as a by product, used this way, which I find a little puzzling...