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Comment by hotpotamus | Hacker News Reader

The theory is that you make "electro fuels" compatible with existing ICE vehicles. The idea is that if the costs of solar keep decreasing and the costs to extract and refine oil keep increasing, you hit an inflection point where this is economically feasible and as a byproduct possibly save the planet.

Here's an example startup https://terraformindustries.com/

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We don't need electro fuels because we want to keep existing ICE vehicles, but rather because energy density is hugely important for fuels -- especially for things like airplanes, which rely on high-density energy sources in order to function. The comparison to direct "solar" power isn't fair; rather, electro fuels should be compared to other energy storage solutions, such as batteries, which have a much lower energy density than fossil fuels.

I don't think it's very smart to bet against technology that is currently at least 50% energy efficient - end to end -, because of density, that can be improved, with thermic engine, which reach less than 30% efficiency, in the engine alone, on best scenarios.

I really don't understand your comment -- can you clarify? Gasoline thus has about 100 times the energy density of a lithium-ion battery. [1] I'm not sure of the numbers, in terms of electrofuels, but I'm sure they're similarly skewed against battery storage. I'm not sure how 50% vs. 30% efficiency of an engine plays much of a role in this.

1. https://www.aps.org/publications/apsnews/201208/backpage.cfm

I'm not speaking about density but efficiency, billions in r&d has been poured into combustion engine r&d and no engine reach more than 30% efficiency on the car sold.

It mean 70% of the energy spent to produce this fuel is going to be lost. Meanwhile batteries range is improving every year, and electric engine easily reach 90% efficiency.

Yes, the idea is that if solar energy is "free" (it's not, but set that aside for sake of argument) then it doesn't matter how inefficient the process is.

The downside of this process seems to be that it doesn't extract atmospheric CO2 to make methanol, it converts CO2 from concentrated industrial waste streams. It's perhaps "better than nothing" but the methanol will probably end up as CO2 again later (if it's used as fuel, for example) so it really isn't as great as it might sound.

Capturing CO2 to be burned elsewhere sounds like releasing half the CO2. Not great, but better?

No, it re-releases all of it.

And a bit more because producing it wasn't free.

But then you're only releasing it once, rather than twice as much. Hence: half.

No, that makes no sense at all. You might as well say you sweat/piss out half as much water as you drink. No: all of it.

You have two things that burn fuel and produce CO2. Thing A burns fuel, its CO2 isn't released but captured. That captured CO2 fuel is then burned at Thing B and released. Half. (if you assume the energy from reprocessing the CO2 into fuel doesn't produce Co2 itself and comes from clean sources)

X tons mined carbon in, X tons atmospheric carbon out. What you do with it on the way doesn't matter. What matters is purely carbon in the atmosphere.

The only thing that does make a difference is if you succeed in getting the carbon back into the ground.

The waste stream from making cement is kinda capture-ish... because the concrete slowly absorbs CO2 as it cures.

> The theory is that you make "electro fuels" compatible with existing ICE vehicles

Outside of classic/antique cars, why would we want to keep existing ICE vehicles long term? After a couple decades, the few remaining ICE vehicle niches will probably still be served by petroleum-derived fuels or bio-methanol, not synthetic hydrocarbons.

Subtrack the emissions and an IC engine has any number of advantages, from range and refuel time, to recycling potential. Steel is far far easier to recycle than any battery tech.

Well, a couple decades from now is still a couple decades away for one thing. For another, some things like long haul trucking or air travel may be harder to directly electrify.

It seems like electric rail would make a great replacement for long-haul trucking.

I can't imagine synthetic hydrocarbon fuels being anywhere near cost competitive with either petroleum or bio derived hydrocarbons in the next couple decades.

Switching long haul trucking to renewable hydrogen would make much more sense, since weight is an issue. Air travel is tougher. In the near term we will start blending waste oil based sustainable aviation fuel. Longer term people have suggested directly burning liquid hydrogen.

The biggest near term CO2 reductions will come from switching to renewables for electricity. We have the tech to make major strides on that front now.

The site I linked originally has a whitepaper on the economics of the business and thinks it should end up cheaper than conventional fossil fuel drilling. I'm not familiar with bio derived hydrocarbons other than ethanol, but that doesn't seem all that promising from anything I've heard about. The founder left his job as a NASA software engineer to start it up, so he's probably not a dummy. He could certainly be wrong though.

Right, the associated talking point is that it might be impossible to replace the worlds cars fast enough to reduce the emissions in the next 5 years. Also some people think battery production will hit a hard limit because of resources. I can’t judge 100% but I have a personal opinion on those points.

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