> We already have an entire, scaled up industry of producing artificial fuel in a non-petrochemical route: It's where the ethanol in your gas tank comes from.

Ethanol as a fuel is mostly a subsidy for US farmers. The net energy gain is low.[1] Ethanol plants need a lot of heat energy to process corn into ethanol. They don't burn their own ethanol for heat; they use natural gas or even coal.[2] If they made their own process heat, which they could, they'd use about half their own output. They wouldn't get the subsidy on that. So they burn other fuels to make ethanol.

That doesn't include the costs of farming the corn.

[1] https://energy.sustainability-directory.com/learn/how-does-t...

[2] https://www.researchgate.net/figure/Energy-use-in-each-of-th...