I don't understand why people bring up only ethanol in this example. What to do with the liquid fuels that are used in the production of liquid fuels? Don't they count as "double-counted" just as much?

I started to elaborate on this point, but yes, these liquids are also double-counted. Any liquid fuel inputs that go into producing a liquid fuel product get double-counted.

But I would also again point out that any portion of biofuels that is actually renewable would not get counted if one just looked at C+C. The relevant metric is somewhere between total liquids and C+C.

And that in turn wuld have a potentially large influence on figuring out a peak, wouldn't it?

If 84 mbd is produced, with that 20:1 EROEI, you lose 4.2 mbd every day, so you have net production of 79.8 mbd. That is quite a difference.

And it would be less important if EROEI stayed the same, but it's getting worse all the time, so you lose ever more, and the numbers reflect reality ever less.

I understand that it would be hard to model, but still feel it's too easily neglected.

You biofuel comment is valid. I guess it would be too much of a stretch to look at natural gas use, like in the tar sands?! It may not be C+C (+NGL), but is sure is a waste of energy. Isn't it more appropriate to count these things in some kind of "energy" form, like calories, or joules, or......?

The 'triple-net' is far far lower than 20:1, when you include indirect costs (hiways, insurance, food transport, etc) and environmental externalities. So as energy becomes more difficult to access, the % allocated to energy sector, wide boundaries and all will increase. How much of the 85 mbpd is required to procure the 85mpbd now is an interesting, important and near impossible question to answer.
..overlooks the portion of ethanol that is a legitimate net addition to liquid fuels.

When the debate is about peak oil how can any biofuel be counted towrds production?

I totally agree and have often wondered why the 2 issues are mixed.
When the debate is about peak oil how can any biofuel be counted towrds production?

Because peak oil is not really the relevant metric. It is peak energy. One could say "Sure, we lost 1 million bpd of oil, but we gained 2 million bpd of ethanol." But an accurate metric has to account for the net of that 2 million bpd of ethanol.

"Because peak oil is not really the relevant metric. It is peak energy"

Do you mean to say "peak liquid fuels"?

Yeh Robert - I'd certainly prefer to keep petroleum on one side (C+C+NGL) and other liquids and other forms of energy that may be used to mitigate the shortfall on the other side of the equation.

Peak energy is what we should be focussed on with PO (C+C+NGL) a subset of that broader debate - IMO.