Humans absolutely can use ethanol for energy. https://en.wikipedia.org/wiki/Ethanol_metabolism We net 7 kcal/g from ethanol, (compare to 9 kcal/g fat, or 4 kcal/g carbohydrate/protein.) There's several intermediate steps, but it's pretty efficient and a dense source of energy.

Much of lipid and protein catabolism also does not rely on glucose as an intermediate. Everything that doesn't get converted to glucose first will get converted to acetyl-CoA (glucose catabolites turn into this too) for use in the Krebs cycle.

Absolutely. Bavarian monks famously invented Bock beer (very rich, high wort density, 7% ABV and above) as nourishment during Lent when they were not allowed to take in solid food.

I've read somewhere that beer was used instead of water in areas where water wasn't safe. IIRC, beer has non-alcoholic calories also. I don't believe one can live on spirits, but it could make you forget you are hungry :)

Edit: I should have read TFA before commenting.

Old saying that my wife's French grandpa liked to say - "I don't drink water, it makes me rust".

Heard it as "Water make iron stomachs rust". Usually everyday beer as a replacement of water was smallbeer/bière de table with 2-3% alcohol.

Yes, humans can derive energy from alcohol.

The system that eventually extracts energy from glucose (the citric acid cycle, also called the Krebs cycle) is involved, after the liver converts the ethanol.

All the calories from the grains or fruits used to make alcoholic drinks don't just evaporate into the ether! "Lite" beers with low calorie contents are a fairly new invention.

If you look back far enough, some early brewing, like that of ancient Egypt, made beer so thick that mugs would often come with straws built into them so people could get past the thick layer of almost-solid grains that would float to the top.

Ethanol is broken down and eventually fed into the TCA cycle. Some useful byproducts are also made. So, yeah, you get some energy out of ethanol. It's a pretty inefficient way to get energy though.

It's an efficient way to get calories up until the year's first harvest though.