On 4/26/2014 11:02 AM, jim wrote:
....

From the EIA site...

"U.S. corn ethanol production grew considerably from 2006 through 2012,
boosted by the phase-out of the use of Methyl tertiary-butyl ether
(MTBE) as an oxygenate and octane enhancer, the availability of blender
tax credits, and rising oil prices. Ethanol production and use grew
beyond levels called for by the RFS as early as 2006. U.S. ethanol
production and use continued at rates beyond the RFS-mandated level
through mid-2012. ..."

Hence, in fact, they _are_ using more than the mandate calls for.

There was more ethanol used than the mandate called
for before mid 2012. At that point usage reached the 10%
ceiling that is the maximum allowed. Ethanol usage would be
higher today if the EPA allowed it to be.

As the above says, "... use grew beyond levels called for by the RFS as
early as 2006...". Perhaps conversations would go more smoothly if you
would actually read first, write second.

Actually, EPA sets no limits; E15 and E85 are approved for use so
there's no 10% limit at all.

It's (like virtually everything in real world, particularly those that
are part of public policy) complicated. The mandate really isn't
ethanol per se, it's "renewable fuel" that's mandated. It just so
happens that current technology, the existence of a large fleet of
gasoline engine vehicles such that whatever fuel alternative used had to
be compatible and feed stocks available for renewable fuels in the US
favor corn ethanol at the moment.


The market place determined that outcome.

Strongly influenced by national policy and technology limitations as well.

Biodiesel and all are included as well; they just don't get the
attention ethanol does as soybeans aren't as cute, apparently.

Yes that is how it saves money. It costs money and energy
to boost octane by converting low octane petroleum
fractions to higher octane fractions.

Cite?
...

That's easily found and well-known and has been in the earlier
subthreads in this thread as well. I wouldn't say it in precisely those
terms but increased refining to build octane from crude oil itself
definitely hurts yield. Refiners used additives for the purpose from
the very beginning; the widespread use of tetraethyl lead began in the
early 20s or thereabouts to allow for increased compression that was
needed for higher performance and thus needed higher octane-rated fuels
to inhibit knocking.

Higher compression is not just about performance. It
is also necessary for efficiency. And it is not just about
thermal efficiency. Higher compression means you can get
more power from a lighter engine. That means the chassis and
suspension can be lighter also.

"Performance" is a generic term which includes all of the above and more...

MTBE was the primary substitute of choice when
unleaded was mandated owing to lead's deleterious health effects and
contamination until it was determined to be as bad or worse for it's
propensity to contaminate water supplies when spilled and carcinogenic
nature. Hence, it also went the way of the dodo bird and ethanol has
the facility to raise octane and meet RFIS as well as lower emissions of
nitrous oxides, etc., ... So, at the moment it's the deal.

When and if something better comes along, it'll surely take it's moment
in the sun as well...


Henry Fords first car ran on ethanol. It has been
used as fuel longer than gasoline.

While true, of little relevance to the present discussion. Sperm oil
was used before crude, too, but hasn't any bearing.

--