I've been brewing ethanol for years. I run my law mower and my enduro motorcycle off it.

I bought a custom made 50L still from Mile High Distillers. Biggest one
They had at the time. I think the biggest prob you would have in a shtf scenario is finding good stuff to ferment to actually get quantity of shine. And quality. Plus yeast doesn't store well so you'll want to learn how to cultivate your own. It can be done I guess.

You can order truckloads of stuff from farmers. But it will rot. Not sure how that would work. I grow Sunchokes. Jerusalem Artichokes. They grow out of control and have a very high sugar content. Much more than corn. At this point they are probably spreading across my county. They are like a sweet potAto. Good to eat too. But they make the best ethanol.

My bike runs great. Same with law mower. They use more fuel than if on gas alone. You need a carb and you'll have to drill the jets out a hair so they run 'rich'. And they need to warm up more. I figured each gallon costs me about .50 cents as a final product not including my labor. It takes time to distill a quality brew if you want the water out. You can't just cook it. Use an electric plate for best temp control and practice practice.

Besides fuel you can drink the stuff as long as you aren't mixing has in. In a collapse scenario having quality booze for cheap will make you a lord.

In hindsight I would probably just buy a large tank and buy 10,000 gallons of diesel. That's more than you'll use in a lifetime. Easier than distilling. Then I'd just brew ethanol for drink to sell. Medicinal purposes. And for lanterns.

It has many important uses. But for fuel for an engine I've learned that it won't be practical in the long run especially for a generator. You're better off with a couple wind generators and solar panels.

Just my thoughts. But definitely get a still. A good one with quality spare parts. Learn the science. Perfect the art.