Butane is a source stock for the production of MTBE which was taken out of most fuels after contamination of environment issues.  Here's an article on it's economics back around 2000 when MTBE was priced HIGHER than straight gasoline and we blended MTBE as an oxeygenate.. later replaced by etoh.

http://www.eia.gov/forecasts/steo/special/pdf/mtbecost.pdf

However, you can also make ETBE out of Butane and ethanol which may (???) alleviate some of the environmental disadvantages that MTBE had... ???  ETBE could ALSO be shippd through pipelines and treated more like straight gasoline.. so it may (??) hold some advantages for ethanol also...???  Certainly if you added the Butane through the ETBE process you would cut down on the total amount of etoh used.. however..???  If we are short on supply anyway...???  would that be all bad...???

There's a growing amount of Butane that currently is cheap.. and adding ETBE would LOWER the cost of gasoline.. use a growing excess amount of Butane WHILE STILL using Ethanol...  I'm not sure it's the direction that we WANT to go.. but it MIGHT (??) be an option to consider...???

The Refiners like it as it uses a waste product stream for them (adds value) as well as kicks off hydrogen which they can use back in their production stream.. THEY WILL However, push maximum butane.. and as noted as we drill in the shale Nat Gas zones.. that supply will grow.. upwards of 100 to 200,000 bbls/day vs current ethanol production of around 800,000 b/d.

Here's a primer pdf on it..

www.efoa.eu/en/cust/documentrequest.aspx?DocID=187

ETBE uses more butane than ethanol for the finished product.. so it could eat into the current ethanol market significantly.. so ethanol would be yielding some ground.. but would still be used.. and probably constrained by the amount of Butane produced.. which ???  We don't really know.. could be some.. could be alot..it's going to continue to grow given the CURRENT environment.

The world looks alot different then it did 13 years ago from the first link above..

and also starting to look a little different then even 5 years ago in 08 when etoh hit it's building boom.. I'm sure some ethanol proponents would be dead set against this.. (myself included...??)  Just don't know.. do you raise a white flag to hold onto what you have.. offering a cheaper option to the consumer?  Or press on.. hoping for a MONSTER 2013 crop...???  If we don't get the crop.. then what...??

fyi.. not advocating.. just saying.. "heads up.. this is on the horizon.."

This would probably be viewed as a triage kind of thing.. amputating a leg (or two) in order to save the patient... "You want to do WHAT?!?" so.. ???

However, Butane is ALSO domestically produced.. currently cheaper.. and a growing supply.. under a couple of scenerio's this "may" be the "right thing to do" as well as "NOT" under others.. Kind of tricky to guess..  What happens in the future?  Back to Monster corn crops?  Or not..???  Take the leg.. or risk the infection..??