[thackney]

The only question is: can this be done efficiently?

If it was perfectly efficient, you could only get out what you put in. But in real world, any process isn't perfect, there is some losses and you get less useful energy out than put in, the balance is losses like heat.

[norraad]

... efficient?, that would be something called gasoline, always has been, always will be, even better if you don't dilute it with taxpayer subsidized corn sweezins’.!