This is the salient point that is glossed over without so much as blinking.
To get 1J of biofuel-based fuel, how many J of fossil fuel is burned? If it’s like 0.9J then you really have to ask how much carbon is released when turning carbon sinks into farmland, because it will take many many crop cycles to recoup that from biofuels.
That is the implementation detail that makes the whole thing a scam, yes. None of that is fundamental to bio-fuels, but rather a property of it being cheaper to do it that way in our current fossil fuel economy, and people not being interested in looking all that closely because they don’t really care.
What is not factored into the above is how much is going to be grown anyway. Corn yield in particular can quickly surprise you. Even if you try to only grow enough for food, there will be years where you still have way more than you can handle.
That is why we started producing corn-based ethanol. It wasn't intended to see people grow corn for it, but rather clean up the unmanageable excesses realized in the due course of growing it for food-based reasons that otherwise would have been left out to rot. In that vein, J is insignificant as it is spent either way.
The problem is that humans aren't very good at moderation. A little ethanol production is quite sensible, but once humans get it into their head something might be sensible in small doses they have to take it to a ridiculous extreme... You see that in everything.
The other issue is people seeing corn for ethanol (especially subsidized) can be waaaay more profitable and deciding to switch crops. Not only do you lose a potentially valuable food crop. But it's replaced by one of the nutrient and GHG intensive crops around
As a corn grower myself, I wouldn't go that far. Ethanol production is really only profitable when corn isn't profitable to grow. In other words, when you have ethanol plants champing at the bit to buy your corn, you are wishing you hadn't grown it in the first place! It can be a profitable crop, but only on the backs of food buyers who are much less price sensitive.
Ethanol does serve as a helpful buffer to step in when corn would be otherwise worthless, where the alternative is to let you see it rot, minimizing the losses — But if you are counting on ethanol to make you rich... Good luck!
Granted, there was that strange period around the early 2010s, in reaction to the early-to-mid 2000s where corn was being left to rot, where the US government was paying ethanol producers to produce ethanol. If you are posting from a time machine from that time, I get what you are saying. But those days are long behind us now.
To get 1J of biofuel-based fuel, how many J of fossil fuel is burned? If it’s like 0.9J then you really have to ask how much carbon is released when turning carbon sinks into farmland, because it will take many many crop cycles to recoup that from biofuels.