Evidently butanol has the rather remarkable property that it can be blended in considerable quantity, with no modifications to engines, to either gasoline or diesel fuel. Sort of a "Type O" universal additive. This raises the interesting prospect that you could have some of the fuel supply cast in butanol, or even some of the tankage at a gas station, and mix it with either to more flexibly adjust to supply and demand shifts. Prices bobbing up and down independently over various refinery issues etc. will be a thing of the past.

Of course, the fuel would need to be sold by the MJ (GGE) instead of by the gallon to account for the slightly variable energy density depending on mixture.

RP
No real downside relative to ethanol that I'm aware of. Ethanol is more common because we've known how to produce it using fermentation for thousands of years. I was easier to scale up grain based ethanol production to begin with. Vested interested? Of course. Many farmers in the USA are being subsidised to produce ethanol and love it. I sympathize. Farming is a tough life and it's tough to do well economically. This is really helping them. Not a good long term policy to use food for fuel though. ...unless the French Revolution on a world scale sounds like fun. I'd rather see cellulosic biobutanol with subsidised food farming.

Ethanol has some problems as a fuel. It is a more polar molecule and mix with water more easily than oil. (h2o is a very polar molecule with + charge at one end and - charge at other. Oil is made of very non-polar hydrocarbon molecules. This is why "oil and water don't mix". They tend to separate into layers.) This is great if you have it in a sealed can and put it in your gas to help dissolve water that is already in there, but not so good if the ethanol is just sitting around because it will draw in water vapor. Think this is the problem with transport ethanol using existing oil pipelines made of steel and why it corrodes these pipelines. Oil pipelines must be maintained as is.

Butanol is better choice for fuel. DuPont and BP are also working together on biobutanol production:

http://www.greencarcongress.com/2006/06/bp_and_dupont_t.html (BP & DuPont partner up for bio-butanol development – Jun 2006)

http://thefraserdomain.typepad.com/energy/2007/03/dupont_provides.html Update on DuPont Bio-Fuels efforts – March 2007

http://www.greencarcongress.com/2007/06/abf-bp-and-dupo.html “ABF, BP and DuPont to Build $400M Bioethanol Plant and Biobutanol Demo Plant” – June 2007.

RP,
You're very welcome. I'm no expert but appreciate anothers interest in this subject. Thank you.

"Does butanol also have this problem?"
No, it does not. It can use existing fuel pipelines. I've read that ethanol has to be shipped by tanker truck.

"Better how?"
1. It can use existing fuel pipeline infrastructure, as just stated.
2. "Evidently butanol has the rather remarkable property that it can be blended in considerable quantity, with no modifications to engines, in either gasoline or diesel fuel." as P Schager and you yourself mention above. Higher concentrations of ethanol require modifications to internal combustion engines. This is where you get all the "flex fuel" vehicle non-sense from Detroit. I'd rather see butanol produced for old vehicles and new vehicle production infrastructure be devoted to PHEVs. Better long term investment.
3. I've read that butanol is better starting substrate for industrial plastics and fertilizer production. (I think ethanol can be used to produce poly-ethalene. I'm not sure about others.) My view is we have started to transition to electric ground tranportation. The battery technology is now here. Costs must come down. The transition will take a long time. (20 years, 30 years?) Long term we will want cellulosic butanol for industrial plastics, not for transportation. Why not plan for that now?

I'm not really sure which has the higher energy density. Can't remember. I have the general impression they are in same ball park. I think compatabiliy with current vehicles is important now and then I think we're going to PHEVs and then possibly EVs, so energy density seems a lesser consideration to me. You don't need to carry as much fuel in a Series PHEV.

I'm also not sure it is better or worse from environmental view point. Probably depends on specific refining/production technology. None of this fuel stuff is very environmentally clean. Industrial refining is a messy business.

I doubt it is any more dangerous than gasoline, but also don't know this.

Butanol is more difficult to produce than ethanol. Otherwise maybe more people would already be doing it. Not sure where you'd go to figure out how to do this. Think this is like cellulosic ethanol. You need to get pretty suffisicated to do it.

You already seem to know some about this.
Hope this helps some.

E85 is rubbish plan and simple. Gasoline real gas not the reformulated crap has 115000 btu/gal. E10 which us Dallasites are forced to buy has 110000-90000 btu a gallon depending on the additive package. Butanol has 110000 btu/gal btw thus its no better than RFG but its world ahead of E85 at 76000 btu/gal. As I commute to Austin on a weekly basis. I get real gas in one city and RFG in another. When I tank up in Dallas I get 285 miles on 15.6 gallons as thats when my fuel alert comes on. On the return trip with an identical 15.6 gals of real gas I get 319 miles till my fuel alert comes on. 225 miles of each tank is wide open motorway at 80 mph each way. The remander is mixed urban/exurban driving in each city. Still on real gas I get 34 more miles in urban traffic of Dallas. My Explorer is Flex fuel and E85 is avalible in the Metroplex but its not economical to use it as you need 1.6 times as much to go the same distance, and its not 62.5% of the cost of RFG. simple economics dictates that one uses RFG not ethanol. For alternative fuels to work they have to be competative in $/per km traveled. Still on this side of the pond fuel is so cheap even at $3 a gallon the average person can afford to drive a Chelsea tractor around solo. There is no underground here in the Metroplex, and the Autobus system is cumbersome to say the least.If one was to chose the autobus plan on spending at least an hour each way to go the 20-30 miles between work and home. Driving the same distance even in peak hour is a 25 min affair. Time is money in my line of work so $3 petro it is. one last point when will you Bloody yanks give up and go metric. having to learn miles and gallons for one country is absurd everyone looks at you like your crazy if you use metric, apparently who cares the rest of the world is standardized. Then again thats the typical attitude here who cares what the world thinks this is America were special. I will say thank you Yanks for makeing me a tiddy living over here, you complain about your tax code and I take great pleasure in paying American taxes compaired to the labor parties mess back home.