Well, yeah, if you can afford it buy solar panels and wind turbines and
batteries.
That's terrific! (No sarcasm, I'm sincere.) In the medium- and long-term we should transition to all-electric
vehicles with renewable and atomic power.
But there's a huge existing fleet of internal-combustion engines
in vehicles, generators, and tools like chainsaws and leaf blowers, etc.
A locally-produced ecologically benign carbon-neutral fuel source is an important part of the solution, eh?
As for efficiency, consider: Scenario A: grow a crop of corn and feed it
to pigs. Scenario B: grow a crop of corn ferment it and extract the
alcohol and feed the leftovers to pigs.
In B you get two crops for the price of one. (Alcohol is produced by
yeast from sugar. The leftovers are protein, the bodies of the yeast.
The corn is a better feed after fermentation and alcohol extraction.)
As for land use in a permaculture farm you would be growing more than one crop
on the same land at the same time. You might have two or three crops
that produce food and some yams or sugar beets for fermentation.
Also, a lot of things you might not realize can be feedstocks. Pretty
much anything with sugar or starch. Farmer Dave had a deal with a donut
bakery to get their scrap dough for fermentation and fuel production.