MIT engineers make converting CO2 into useful products more practical

Isn't it also used as input to basically every e-fuel which can replace fossil hydrocarbons?

No. The value of commercial co2 is its energy content -- what it takes to process it into useful form. There is no useful form of co2 for making fuel. The energy has already been extracted.

You're right (current state of the art), but also wrong (in the spirit of the question as I read it).

If energy prices go down, e.g., from continuing decline of solar, then it may be very cost effective to store energy as hydrocarbons which are synthesized from cheap energy + CO2. E.g., make natural gas from the air and sell it cheaper than it could be extracted and transported.

In this scenario, rather than paying exorbitant fees for CO2, the cheap energy could be used to extract it from the atmosphere where it is abundant.

Before anyone bites my head off - consider the tyranny-of-the-rocket-equation problem of burning gas to transport gas from source (wells, refineries, etc) to consumers. Then consider that the sun shines most places, and CO2 is effectively uniformly distributed. So Synthesis wouldn't have to be cheaper at the source if it can beat the price at the consumer via avoiding huge distribution costs.

Exactly right. FTA: "The electrochemical process that converts CO2 into ethylene involves a water-based solution and a catalyst material, which come into contact along with an electric current"

That "electric current" is the challenge. It takes energy to convert CO2 into other chemicals. If that energy isn't carbon-neutral, you're just spinning your wheels.

I'm not sure if we are talking past each other, but: https://en.wikipedia.org/wiki/Electrofuel

Electrofuels, also known as e-fuels, are a class of synthetic fuels which function as drop-in replacement fuels for internal combustion engines. They are manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen obtained from water split.

It is my understanding that there is actually a shortage of concentrated co2 if we want to produce e-fuels as drop-in replacements in e.g. planes.

> If that energy isn't carbon-neutral, you're just spinning your wheels.

True, but the "long term" angle here would be to supply that energy from, say, excess solar generation during midday after the overnight storage batteries are refilled.

All ideas for "fuels" hinge on the future availability of an economical energy source, which would have to be either solar or nuclear.

I wonder what happened to the Navy's attempts at synthesize aviation fuel in aircraft carriers. They have plenty of power (newer carriers have even more) and reducing or eliminating the need of support craft for fueling would be a massive bonus.

They've been looking at that for a while, I don't know what issues they encountered.

They couldn't get it to be efficient enough.

Yes of course, I am not claiming otherwise.

My point was just about the scarcity of concentrated co2.